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Alex
02-01-2000, 11:35 PM
Found the sources of the cooling system overheating, bad thermostat and insufficient bleeding. The thermostat would not open so the water pump simply pumped hot coolant through the block and cylinder head. Typically, when the thermostat is open, "cool" coolant is drawn from the bottom radiator hose, and "hot" coolant is returned to the radiator via the top hose. After replacing the thermostat, I had to bleed LOTS of air out of the system, more than likely from air pockets in the radiator.<p>I originally diagnosed the leaking head gasket from several observations. The car would cool normally except during prolonged periods of idling when the temperature would climb fairly rapidly into the red zone. The radiator, hoses, and water pump were all reasonably new (less than one year old) so I thought fan clutch. I then replaced the fan clutch but no difference. Next, I noticed that the radiator hoses were very hard and difficult to squeeze. Too much pressure in the system? I then replaced the pressure cap on the coolant reservoir (which is under a BMW recall campaign). Still no difference. It was then I noticed crud at the bottom of the coolant reservoir. Not oil type crud, but light-colored junk. After soliciting the help of several knowledgeable people it appeared that the probable cause was a leaking gasket causing exhaust gases to be forced into the coolant system. This would explain the increased pressure in the system and the "crud" was probably bits of gasket. This diagnosis was confirmed after removal of the cylinder head. The head gasket around one of the coolant channels on #6 cylinder was badly corroded. Even the metal reinforcing ring on the gasket had been eaten away. I cannot state categorically that this was the source of the problem but it definitely seems a distinct possibility. Only time will tell.<p><br>Alex<br>92 735i 167k miles<br>72 2002 187k miles<p>

George
02-02-2000, 08:38 AM
<i>:<br>Alex,<br>Congrats on finding your overheating problem. Just curious if your engine had any missfire <br>associated with the leaky headgasket?<br>Also, was it a big job to pull the head off your big six?<p>Best Regards,<br>George<br>90 735il/138K<p>Found the sources of the cooling system overheating, bad thermostat and insufficient bleeding. The thermostat would not open so the water pump simply pumped hot coolant through the block and cylinder head. Typically, when the thermostat is open, "cool" coolant is drawn from the bottom radiator hose, and "hot" coolant is returned to the radiator via the top hose. After replacing the thermostat, I had to bleed LOTS of air out of the system, more than likely from air pockets in the radiator.<p>: I originally diagnosed the leaking head gasket from several observations. The car would cool normally except during prolonged periods of idling when the temperature would climb fairly rapidly into the red zone. The radiator, hoses, and water pump were all reasonably new (less than one year old) so I thought fan clutch. I then replaced the fan clutch but no difference. Next, I noticed that the radiator hoses were very hard and difficult to squeeze. Too much pressure in the system? I then replaced the pressure cap on the coolant reservoir (which is under a BMW recall campaign). Still no difference. It was then I noticed crud at the bottom of the coolant reservoir. Not oil type crud, but light-colored junk. After soliciting the help of several knowledgeable people it appeared that the probable cause was a leaking gasket causing exhaust gases to be forced into the coolant system. This would explain the increased pressure in the system and the "crud" was probably bits of gasket. This diagnosis was confirmed after removal of the cylinder head. The head gasket around one of the coolant channels on #6 cylinder was badly corroded. Even the metal reinforcing ring on the gasket had been eaten away. I cannot state categorically that this was the source of the problem but it definitely seems a distinct possibility. Only time will tell.<p>: <br>: Alex<br>: 92 735i 167k miles<br>: 72 2002 187k miles<p></i>

Alex
02-02-2000, 07:52 PM
<i>: :<br>: Alex,<br>: Congrats on finding your overheating problem. Just curious if your engine had any missfire <br>: associated with the leaky headgasket?<br>: Also, was it a big job to pull the head off your big six?<p>: Best Regards,<br>: George<p><br>George,<p>No, no misfiring, just loped a little while idling. Not much, perhaps +/- 50 rpm. This loping has now disappeared. Misfiring is typically caused by the ignition system, either a bad coil, bad distributor cap or rotor, or bad plug wire/spark plug. You might also want to check that the crankshaft sensor is not loose, and the induction wire on #1 spark plug wire is firmly attached to its connector on the black plastic box beside the fuel rail.<p>Removing the head was, how can you say, challenging. I originally followed the workshop manual instructions but was stumped when trying to remove the electrical connectros on the fuel injectors. On three separate occasions, I tried unsuccessfully to remove the connectors. Each time I had to re-connect everything again after failing as I couldn't keep the car out of commission for a long period of time. Finally, I solicited the help of Dan Patzer who recommended leaving the intake manifold in the car, complete with fuel injectors and fuel rail, and simply remove the head. This trick really worked. Disconnecting the inlet manifold from the head was tricky especially the nuts on the underside (I have the permanent wounds to prove this). All in all, head removal took about 2 to 3 hours. By comparison, I can remove the head on the 2002 with both manifolds still connected in about 40 minutes.<p><p>: Found the sources of the cooling system overheating, bad thermostat and insufficient bleeding. The thermostat would not open so the water pump simply pumped hot coolant through the block and cylinder head. Typically, when the thermostat is open, "cool" coolant is drawn from the bottom radiator hose, and "hot" coolant is returned to the radiator via the top hose. After replacing the thermostat, I had to bleed LOTS of air out of the system, more than likely from air pockets in the radiator.<p>: : I originally diagnosed the leaking head gasket from several observations. The car would cool normally except during prolonged periods of idling when the temperature would climb fairly rapidly into the red zone. The radiator, hoses, and water pump were all reasonably new (less than one year old) so I thought fan clutch. I then replaced the fan clutch but no difference. Next, I noticed that the radiator hoses were very hard and difficult to squeeze. Too much pressure in the system? I then replaced the pressure cap on the coolant reservoir (which is under a BMW recall campaign). Still no difference. It was then I noticed crud at the bottom of the coolant reservoir. Not oil type crud, but light-colored junk. After soliciting the help of several knowledgeable people it appeared that the probable cause was a leaking gasket causing exhaust gases to be forced into the coolant system. This would explain the increased pressure in the system and the "crud" was probably bits of gasket. This diagnosis was confirmed after removal of the cylinder head. The head gasket around one of the coolant channels on #6 cylinder was badly corroded. Even the metal reinforcing ring on the gasket had been eaten away. I cannot state categorically that this was the source of the problem but it definitely seems a distinct possibility. Only time will tell.<p>: : <br>: : Alex<br>: : 92 735i 167k miles<br>: : 72 2002 187k miles<p></i>

Stefan Borch
02-03-2000, 05:17 AM
Alex,<br>Now you've got me curious too! The cylinder ID sensor is on the wire leading to the plug closest to the passenger compartment on my car (1987, yet still E32), but if I read you posting correct, that is not the right wire?<p>Any comments?<br>Stefan

George
02-03-2000, 01:46 PM
<i>: : :<br>: : <br>Alex,<br>Thanks for the update. Wondered what it was like<br>to pull off the head. I too have tried without<br>success to pull the connectors off the injectors.<br>Was afraid to pull too hard...they are seriously<br>on there. As I have posted, I have been chasing<br>a small missfire in neutral/park between 1800 and<br>2900 rpm. Appreciate your comments about the <br>ignition system. I have a new coil, new plugs (old ones looked good) wire resistance was good<br>etc. Cleaned and set gap on Crank Position Sensor.<br>I haven't ruled out this sensor is acting up or<br>the inductive wire isn't conducting as it should.<br>Any further comments would be appreciated.<br>Best Regards,<br>George<br>90 735il/138K<p>: <br>: George,<p>: No, no misfiring, just loped a little while idling. Not much, perhaps +/- 50 rpm. This loping has now disappeared. Misfiring is typically caused by the ignition system, either a bad coil, bad distributor cap or rotor, or bad plug wire/spark plug. You might also want to check that the crankshaft sensor is not loose, and the induction wire on #1 spark plug wire is firmly attached to its connector on the black plastic box beside the fuel rail.<p>: Removing the head was, how can you say, challenging. I originally followed the workshop manual instructions but was stumped when trying to remove the electrical connectros on the fuel injectors. On three separate occasions, I tried unsuccessfully to remove the connectors. Each time I had to re-connect everything again after failing as I couldn't keep the car out of commission for a long period of time. Finally, I solicited the help of Dan Patzer who recommended leaving the intake manifold in the car, complete with fuel injectors and fuel rail, and simply remove the head. This trick really worked. Disconnecting the inlet manifold from the head was tricky especially the nuts on the underside (I have the permanent wounds to prove this). All in all, head removal took about 2 to 3 hours. By comparison, I can remove the head on the 2002 with both manifolds still connected in about 40 minutes.<p><br>: : Found the sources of the cooling system overheating, bad thermostat and insufficient bleeding. The thermostat would not open so the water pump simply pumped hot coolant through the block and cylinder head. Typically, when the thermostat is open, "cool" coolant is drawn from the bottom radiator hose, and "hot" coolant is returned to the radiator via the top hose. After replacing the thermostat, I had to bleed LOTS of air out of the system, more than likely from air pockets in the radiator.<p>: : : I originally diagnosed the leaking head gasket from several observations. The car would cool normally except during prolonged periods of idling when the temperature would climb fairly rapidly into the red zone. The radiator, hoses, and water pump were all reasonably new (less than one year old) so I thought fan clutch. I then replaced the fan clutch but no difference. Next, I noticed that the radiator hoses were very hard and difficult to squeeze. Too much pressure in the system? I then replaced the pressure cap on the coolant reservoir (which is under a BMW recall campaign). Still no difference. It was then I noticed crud at the bottom of the coolant reservoir. Not oil type crud, but light-colored junk. After soliciting the help of several knowledgeable people it appeared that the probable cause was a leaking gasket causing exhaust gases to be forced into the coolant system. This would explain the increased pressure in the system and the "crud" was probably bits of gasket. This diagnosis was confirmed after removal of the cylinder head. The head gasket around one of the coolant channels on #6 cylinder was badly corroded. Even the metal reinforcing ring on the gasket had been eaten away. I cannot state categorically that this was the source of the problem but it definitely seems a distinct possibility. Only time will tell.<p>: : : <br>: : : Alex<br>: : : 92 735i 167k miles<br>: : : 72 2002 187k miles<p></i>

Alex
02-03-2000, 08:55 PM
<i>: Alex,<br>: Now you've got me curious too! The cylinder ID sensor is on the wire leading to the plug closest to the passenger compartment on my car (1987, yet still E32), but if I read you posting correct, that is not the right wire?<p>: Any comments?<br>: Stefan<p><br>Stefan,<p>You are absolutely right, I was wrong. I just checked. The cylinder id sensor is on the plug wire for #6 cylinder. This is the cylinder closest to the firewall. Sorry about that. I can replace a head gasket but cannot tell the difference between a 1 and a 6. It was dark outside, that's my story and I'm sticking to it.<p>Alex<p><br></i>

Alex
02-03-2000, 09:01 PM
George,<p>With the misfiring, you might want to try the trick of running the car in a darkened garage with the hood open. Bad spark plug wires will show arcing between the wires and the body or block. Heat (of which there is a lot in the E32 engine compartment) causes internal breakdown of the spark plug wires. It's a very easy test and will instantly show you if there is a wire problem. Let us know what you find.<p>Alex<br></i>

George
02-04-2000, 08:49 AM
<i>: <br>Alex,<br>Tried the dark garage trick some time ago....<br>learned this on a previous car...no luck...no<br>arcing. Also performed a resistance check of all the wires and all tested good. Also replaced<br>cap, rotor and coil. Going to have to find a good<br>scope to try to isolate whether the problem is<br>ignition vs. air/fuel. As a wildcard, it could be<br>carboned valves...have run multiple tanks of gas<br>treatment however. Odd thing is miss is only discernible in neutral/park without load....miss is slight...not as extreme as pulling off a plug wire. Also spark plug coloration is good for all plugs so they are all firing. Car pulls steadily under load...no miss.<br>Fuel economy is average, i.e. 18 mpg city/highway<br>average. The mystery continues.<br>Best Regards,<br>George<br>90 735il/138K<p><p><br>George,<p>: With the misfiring, you might want to try the trick of running the car in a darkened garage with the hood open. Bad spark plug wires will show arcing between the wires and the body or block. Heat (of which there is a lot in the E32 engine compartment) causes internal breakdown of the spark plug wires. It's a very easy test and will instantly show you if there is a wire problem. Let us know what you find.<p>: Alex<p></i>

Alex
02-04-2000, 07:15 PM
<i>: : <br>: Alex,<br>: Tried the dark garage trick some time ago....<br>: learned this on a previous car...no luck...no<br>: arcing. Also performed a resistance check of all the wires and all tested good. Also replaced<br>: cap, rotor and coil. Going to have to find a good<br>: scope to try to isolate whether the problem is<br>: ignition vs. air/fuel. As a wildcard, it could be<br>: carboned valves...have run multiple tanks of gas<br>: treatment however. Odd thing is miss is only discernible in neutral/park without load....miss is slight...not as extreme as pulling off a plug wire. Also spark plug coloration is good for all plugs so they are all firing. Car pulls steadily under load...no miss.<br>: Fuel economy is average, i.e. 18 mpg city/highway<br>: average. The mystery continues.<br>: Best Regards,<br>: George<br>: 90 735il/138K<p><br>: <br>George,<p>Interesting that you mentioned that the "miss" occurs in neutral under no load and is not as noticeable as removing a spark plug wire. Could you perhaps have a faulty idle speed regulator or a sticking flap in the throttle body? I would try removing the idle speed stabilizer and spraying it with carburetor cleaner. I would also do the same for the airflow meter and he throttle body. It made a discernable difference on my car a while back.<p>Alex<br>

George
02-07-2000, 08:59 AM
<i>: : : <br>: :<br>Thanks Alex for your continued responses.<br>I've done quite a bit to great rid of this annoy-<br>ing miss between 1500 and 2800 rpm. As to the idle speed regulator or Idle Control Valve...a couple of comments. 1)Think this device only affects idle speed....my miss seems to be at slightly higher RPM...please correct me if I'm<br>wrong about this....Yes I have removed it and run<br>carb cleaner thru it. 2)As to Air-Flow Meter and<br>Throttle butterfly...yes I have looked at these as<br>well. Both seem functional and I also cleaned both with carb cleaner. Again don't know if its<br>ignition vs. air/fuel. Need to find a scope to<br>isolate one or the other. I am sure open to any<br>other ideas...thanks again Alex.<br>George<br>90 735il/138K<br> <br> <p><br> <p>Alex,<br>: : Tried the dark garage trick some time ago....<br>: : learned this on a previous car...no luck...no<br>: : arcing. Also performed a resistance check of all the wires and all tested good. Also replaced<br>: : cap, rotor and coil. Going to have to find a good<br>: : scope to try to isolate whether the problem is<br>: : ignition vs. air/fuel. As a wildcard, it could be<br>: : carboned valves...have run multiple tanks of gas<br>: : treatment however. Odd thing is miss is only discernible in neutral/park without load....miss is slight...not as extreme as pulling off a plug wire. Also spark plug coloration is good for all plugs so they are all firing. Car pulls steadily under load...no miss.<br>: : Fuel economy is average, i.e. 18 mpg city/highway<br>: : average. The mystery continues.<br>: : Best Regards,<br>: : George<br>: : 90 735il/138K<p>: <br>: : <br>: George,<p>: Interesting that you mentioned that the "miss" occurs in neutral under no load and is not as noticeable as removing a spark plug wire. Could you perhaps have a faulty idle speed regulator or a sticking flap in the throttle body? I would try removing the idle speed stabilizer and spraying it with carburetor cleaner. I would also do the same for the airflow meter and he throttle body. It made a discernable difference on my car a while back.<p>: Alex<br>: <p></i>

John
02-08-2000, 12:08 PM
George<p>Got the same thing here. Just a slight rumble while in neutral, smooth as velvet in Drive??<p>Gone through your's and Alex's checklist to no avail. How about a tired O2 sensor?? Mine now has 90K miles on it. What is the status of yours??<p>John 88 735iL (226K)<br>79 320i (250K)<br>95 Disco<p><i>: : : : <br>: : :<br>: Thanks Alex for your continued responses.<br>: I've done quite a bit to great rid of this annoy-<br>: ing miss between 1500 and 2800 rpm. As to the idle speed regulator or Idle Control Valve...a couple of comments. 1)Think this device only affects idle speed....my miss seems to be at slightly higher RPM...please correct me if I'm<br>: wrong about this....Yes I have removed it and run<br>: carb cleaner thru it. 2)As to Air-Flow Meter and<br>: Throttle butterfly...yes I have looked at these as<br>: well. Both seem functional and I also cleaned both with carb cleaner. Again don't know if its<br>: ignition vs. air/fuel. Need to find a scope to<br>: isolate one or the other. I am sure open to any<br>: other ideas...thanks again Alex.<br>: George<br>: 90 735il/138K<br>: <br>: <p>: <br>: <p>: Alex,<br>: : : Tried the dark garage trick some time ago....<br>: : : learned this on a previous car...no luck...no<br>: : : arcing. Also performed a resistance check of all the wires and all tested good. Also replaced<br>: : : cap, rotor and coil. Going to have to find a good<br>: : : scope to try to isolate whether the problem is<br>: : : ignition vs. air/fuel. As a wildcard, it could be<br>: : : carboned valves...have run multiple tanks of gas<br>: : : treatment however. Odd thing is miss is only discernible in neutral/park without load....miss is slight...not as extreme as pulling off a plug wire. Also spark plug coloration is good for all plugs so they are all firing. Car pulls steadily under load...no miss.<br>: : : Fuel economy is average, i.e. 18 mpg city/highway<br>: : : average. The mystery continues.<br>: : : Best Regards,<br>: : : George<br>: : : 90 735il/138K<p>: : <br>: : : <br>: : George,<p>: : Interesting that you mentioned that the "miss" occurs in neutral under no load and is not as noticeable as removing a spark plug wire. Could you perhaps have a faulty idle speed regulator or a sticking flap in the throttle body? I would try removing the idle speed stabilizer and spraying it with carburetor cleaner. I would also do the same for the airflow meter and he throttle body. It made a discernable difference on my car a while back.<p>: : Alex<br>: : <p></i>

Alex
02-08-2000, 01:29 PM
<i>: George<p>: Got the same thing here. Just a slight rumble while in neutral, smooth as velvet in Drive??<p>: Gone through your's and Alex's checklist to no avail. How about a tired O2 sensor?? Mine now has 90K miles on it. What is the status of yours??<p>: John 88 735iL (226K)<br>: 79 320i (250K)<br>: 95 Disco<p><br>John,<p>A faulty O2 sensor would probably cause the engine to run too rich. This would show up on the spark plugs. George's spark plugs seem to be okay. I am now wondering if the problem is an air or vacuum leak somewhere, assuming it it the fuel system that is causing the problem. It might be worth checking around the following places:<p>- inlet manifold where it attaches to the head<br>- vacuum line that attaches to fuel presure regulator and underside of inlet manifold<br>- rubber hose that runs from inlet manifold to valve cover<br>- large hoses that connect the airflow meter and the throttle body<br>- the small rubber hose that connects to the right hand side of the airflow meter (opposite side to idle stabilizer valve). There is also a small vacuum line that attaches to this hose.<p>The best way I have found to detect leaks is to spray the suspected area with soapy water. The problem with using WD40 or something similar to increase the idle is that these cars have adaptive control systems and will automatically compensate. Good luck.<p>Alex<br>1992 735i 167k miles (runs cool but lots of valve train noise)<br>1972 2002 187k miles (oh, if only everything was this simple)<br>

George
02-09-2000, 09:01 AM
<i>: :<br>Hey John and Alex,<br>Alex is right, O2 failure should show up in the coloration of the plugs...mine looked fine...<br>changed them anyway when I performed a compression<br>check. Also believe O2 malfunction is more a <br>transient throttle issue....would be more of a <br>hesitation when tipping the throttle....old O2<br>sensors are slow or unresponsive to resistance<br>change telling the DME to quickly change air/fuel<br>ratio. My missfire is at steady state/constant throttle position in neutral. Thanks Alex for all your tips. You have me thinking again about a potential vacuum leak. I have done most of the stuff you listed with the exception of checking inlet manifold to head....replaced all the small vacuum lines and big AFM bellows.<br>I will try the soapy water technique on my intake.<br>John, I was wondering what your miss is like?<br>Mine is like: mmmmmmmmmmmmmmmmftmmmmmmmmmmmftftmmmmmmmmmmmmmmmm<br>There is another fellow on the board, A.T. with<br>the same problem. We have been corresponding as<br>well. Last I heard, he was going to change his<br>throttle position sensor. Please post any further<br>findings/recommendations and thanks again every-<br>one. <p>Best Regards,<br>George<br>90 735il/138K<br> <p><p><p><p><p><br>eorge<p>: : Got the same thing here. Just a slight rumble while in neutral, smooth as velvet in Drive??<p>: : Gone through your's and Alex's checklist to no avail. How about a tired O2 sensor?? Mine now has 90K miles on it. What is the status of yours??<p>: : John 88 735iL (226K)<br>: : 79 320i (250K)<br>: : 95 Disco<p>: <br>: John,<p>: A faulty O2 sensor would probably cause the engine to run too rich. This would show up on the spark plugs. George's spark plugs seem to be okay. I am now wondering if the problem is an air or vacuum leak somewhere, assuming it it the fuel system that is causing the problem. It might be worth checking around the following places:<p>: - inlet manifold where it attaches to the head<br>: - vacuum line that attaches to fuel presure regulator and underside of inlet manifold<br>: - rubber hose that runs from inlet manifold to valve cover<br>: - large hoses that connect the airflow meter and the throttle body<br>: - the small rubber hose that connects to the right hand side of the airflow meter (opposite side to idle stabilizer valve). There is also a small vacuum line that attaches to this hose.<p>: The best way I have found to detect leaks is to spray the suspected area with soapy water. The problem with using WD40 or something similar to increase the idle is that these cars have adaptive control systems and will automatically compensate. Good luck.<p>: Alex<br>: 1992 735i 167k miles (runs cool but lots of valve train noise)<br>: 1972 2002 187k miles (oh, if only everything was this simple)<p></i>

John
02-09-2000, 12:00 PM
George<p>No, my misfires/stumbles are more prevalent. Roughly approximates two runs through the firing order but not quite. The strange thing about it is how just the threat of putting it into Drive eliminates it. The split second before the tranny engages you can already detect that it has smoothed out.<p>And it is not even that bad, just an annoyance has I recall how smooth it used to be!! Me, who spends time each week in one of these turbo-diesel pickups should be complaining???<p>John 88 735iL (226K)<br>79 320i (250K)<br>95 Disco<p><br><i>: : :<p>: Mine is like: mmmmmmmmmmmmmmmmftmmmmmmmmmmmftftmmmmmmmmmmmmmmmm<br>: There is another fellow on the board, A.T. with<br>: the same problem. We have been corresponding as<br>: well. <br>: Best Regards,<br>: George<br>: 90 735il/138K<br>: <p><p><p>: <br>: eorge<p>: : : Got the same thing here. Just a slight rumble while in neutral, smooth as velvet in Drive??<p>: : : Gone through your's and Alex's checklist to no avail. How about a tired O2 sensor?? Mine now has 90K miles on it. What is the status of yours??<p>: : : John 88 735iL (226K)<br>: : : 79 320i (250K)<br>: : : 95 Disco<p>: : <br>: : John,<p>: : A faulty O2 sensor would probably cause the engine to run too rich. This would show up on the spark plugs. George's spark plugs seem to be okay. I am now wondering if the problem is an air or vacuum leak somewhere, assuming it it the fuel system that is causing the problem. It might be worth checking around the following places:<p>: : - inlet manifold where it attaches to the head<br>: : - vacuum line that attaches to fuel presure regulator and underside of inlet manifold<br>: : - rubber hose that runs from inlet manifold to valve cover<br>: : - large hoses that connect the airflow meter and the throttle body<br>: : - the small rubber hose that connects to the right hand side of the airflow meter (opposite side to idle stabilizer valve). There is also a small vacuum line that attaches to this hose.<p>: : The best way I have found to detect leaks is to spray the suspected area with soapy water. The problem with using WD40 or something similar to increase the idle is that these cars have adaptive control systems and will automatically compensate. Good luck.<p>: : Alex<br>: : 1992 735i 167k miles (runs cool but lots of valve train noise)<br>: : 1972 2002 187k miles (oh, if only everything was this simple)<p></i>

Alex
02-09-2000, 06:39 PM
George/John,<p>A couple of "stupid" things to check for air/vacuum leaks. Is the oil dipstick sealing properly? What about the oil cap on the valve cover?<p>Alex<p><br><i>: : :<br>: Hey John and Alex,<br>: Alex is right, O2 failure should show up in the coloration of the plugs...mine looked fine...<br>: changed them anyway when I performed a compression<br>: check. Also believe O2 malfunction is more a <br>: transient throttle issue....would be more of a <br>: hesitation when tipping the throttle....old O2<br>: sensors are slow or unresponsive to resistance<br>: change telling the DME to quickly change air/fuel<br>: ratio. My missfire is at steady state/constant throttle position in neutral. Thanks Alex for all your tips. You have me thinking again about a potential vacuum leak. I have done most of the stuff you listed with the exception of checking inlet manifold to head....replaced all the small vacuum lines and big AFM bellows.<br>: I will try the soapy water technique on my intake.<br>: John, I was wondering what your miss is like?<br>: Mine is like: mmmmmmmmmmmmmmmmftmmmmmmmmmmmftftmmmmmmmmmmmmmmmm<br>: There is another fellow on the board, A.T. with<br>: the same problem. We have been corresponding as<br>: well. Last I heard, he was going to change his<br>: throttle position sensor. Please post any further<br>: findings/recommendations and thanks again every-<br>: one. <p>: Best Regards,<br>: George<br>: 90 735il/138K<br>: <p><p><p>: <br>: eorge<p>: : : Got the same thing here. Just a slight rumble while in neutral, smooth as velvet in Drive??<p>: : : Gone through your's and Alex's checklist to no avail. How about a tired O2 sensor?? Mine now has 90K miles on it. What is the status of yours??<p>: : : John 88 735iL (226K)<br>: : : 79 320i (250K)<br>: : : 95 Disco<p>: : <br>: : John,<p>: : A faulty O2 sensor would probably cause the engine to run too rich. This would show up on the spark plugs. George's spark plugs seem to be okay. I am now wondering if the problem is an air or vacuum leak somewhere, assuming it it the fuel system that is causing the problem. It might be worth checking around the following places:<p>: : - inlet manifold where it attaches to the head<br>: : - vacuum line that attaches to fuel presure regulator and underside of inlet manifold<br>: : - rubber hose that runs from inlet manifold to valve cover<br>: : - large hoses that connect the airflow meter and the throttle body<br>: : - the small rubber hose that connects to the right hand side of the airflow meter (opposite side to idle stabilizer valve). There is also a small vacuum line that attaches to this hose.<p>: : The best way I have found to detect leaks is to spray the suspected area with soapy water. The problem with using WD40 or something similar to increase the idle is that these cars have adaptive control systems and will automatically compensate. Good luck.<p>: : Alex<br>: : 1992 735i 167k miles (runs cool but lots of valve train noise)<br>: : 1972 2002 187k miles (oh, if only everything was this simple)<p></i><br>

George
02-10-2000, 10:02 AM
<i>: <br>Alex,<br>Yeah, I found out early that the valve train was<br>under vacuum when I tried to purchase a PCV valve.<br>As you well know, there isn't a PCV valve for the<br>Big Six/M-30 and everything is under vacuum.<br>Seems like O-rings on dipstick and valve cover<br>cap are tight. Will definitely check intake manifold with soapy water technique per your<br>recommendation. The more I think about it, a <br>vaccum leak seems to have merit because my 7 pulls<br>pretty hard without a miss under load. Under load, correct me if I'm wrong, the motor pulls more vaccum than the same throttle position without load. May explain why my missfire only<br>occurs without load.....motor may be starving for<br>more vacuum.<br>Of course will keep you posted with any progress<br>and thanks again Alex.<br>George <br> <p><p><br>George/John,<br>A couple of "stupid" things to check for air/vacuum leaks. Is the oil dipstick sealing properly? What about the oil cap on the valve cover?<p>: Alex<p>: <br>: : : :<br>: : Hey John and Alex,<br>: : Alex is right, O2 failure should show up in the coloration of the plugs...mine looked fine...<br>: : changed them anyway when I performed a compression<br>: : check. Also believe O2 malfunction is more a <br>: : transient throttle issue....would be more of a <br>: : hesitation when tipping the throttle....old O2<br>: : sensors are slow or unresponsive to resistance<br>: : change telling the DME to quickly change air/fuel<br>: : ratio. My missfire is at steady state/constant throttle position in neutral. Thanks Alex for all your tips. You have me thinking again about a potential vacuum leak. I have done most of the stuff you listed with the exception of checking inlet manifold to head....replaced all the small vacuum lines and big AFM bellows.<br>: : I will try the soapy water technique on my intake.<br>: : John, I was wondering what your miss is like?<br>: : Mine is like: mmmmmmmmmmmmmmmmftmmmmmmmmmmmftftmmmmmmmmmmmmmmmm<br>: : There is another fellow on the board, A.T. with<br>: : the same problem. We have been corresponding as<br>: : well. Last I heard, he was going to change his<br>: : throttle position sensor. Please post any further<br>: : findings/recommendations and thanks again every-<br>: : one. <p>: : Best Regards,<br>: : George<br>: : 90 735il/138K<br>: : <p><p>: : <br>: : eorge<p>: : : : Got the same thing here. Just a slight rumble while in neutral, smooth as velvet in Drive??<p>: : : : Gone through your's and Alex's checklist to no avail. How about a tired O2 sensor?? Mine now has 90K miles on it. What is the status of yours??<p>: : : : John 88 735iL (226K)<br>: : : : 79 320i (250K)<br>: : : : 95 Disco<p>: : : <br>: : : John,<p>: : : A faulty O2 sensor would probably cause the engine to run too rich. This would show up on the spark plugs. George's spark plugs seem to be okay. I am now wondering if the problem is an air or vacuum leak somewhere, assuming it it the fuel system that is causing the problem. It might be worth checking around the following places:<p>: : : - inlet manifold where it attaches to the head<br>: : : - vacuum line that attaches to fuel presure regulator and underside of inlet manifold<br>: : : - rubber hose that runs from inlet manifold to valve cover<br>: : : - large hoses that connect the airflow meter and the throttle body<br>: : : - the small rubber hose that connects to the right hand side of the airflow meter (opposite side to idle stabilizer valve). There is also a small vacuum line that attaches to this hose.<p>: : : The best way I have found to detect leaks is to spray the suspected area with soapy water. The problem with using WD40 or something similar to increase the idle is that these cars have adaptive control systems and will automatically compensate. Good luck.<p>: : : Alex<br>: : : 1992 735i 167k miles (runs cool but lots of valve train noise)<br>: : : 1972 2002 187k miles (oh, if only everything was this simple)<p><br></i>


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