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Paul H
12-16-1998, 11:59 PM
I am certain this has been discussed before, so apologies up front, but...<p>I get an occasional engine "miss". It will only occur on a light throttle (never under load), and can be triggered by going over a bump. If a bump does trigger it, there is a small delay (1-2 seconds), and the engine will then miss once or twice.<p>I started to wonder if some sensor might be a little loose, but what?<p>If anyone has had this behaviour in their E34, and has a fix, I'd like to hear about it.<p>TIA. Paul.<br>

Paul H
12-17-1998, 02:27 AM
<i>: I am certain this has been discussed before, so apologies up front, but...<p>: I get an occasional engine "miss". It will only occur on a light throttle (never under load), and can be triggered by going over a bump. If a bump does trigger it, there is a small delay (1-2 seconds), and the engine will then miss once or twice.<p>: I started to wonder if some sensor might be a little loose, but what?<p>: If anyone has had this behaviour in their E34, and has a fix, I'd like to hear about it.<p>: TIA. Paul.<p></i><p>Further to this, I got an inspection II done today, and mentioned the problem to the mechanic.<p>The diagnostics came up with an error 29 - Road speed signal. The mechanic said the sensor is in the diff, but he had to get some more info about the type of problems associated with it.<p>Is this likely to have any significance with respect to the engine misses?<p>Paul.<br>

Andy Peavy
12-17-1998, 10:12 AM
<i>: The diagnostics came up with an error 29 - Road speed signal. The mechanic said the sensor is in the diff, but he had to get some more info about the type of problems associated with it.<p>: Is this likely to have any significance with respect to the engine misses?<br></i><p>I'm going to say YES, because this has happened to my car and I have noticed that it occurs when the rear wheels hit sharp, but small bumps.<p>I have yet to find a solution, and I know there are more than a few who have cars with this symptom.<p>Please post any information your mechanic comes up with...<p>Andy Peavy<br>91 535i<br>email: apeavy@yahoo.com

Jon Brush
12-17-1998, 01:16 PM
<br>: : I am certain this has been discussed before, so apologies up front, but...<p>: : I get an occasional engine "miss". It will only occur on a light throttle (never under load), and can be triggered by going over a bump. If a bump does trigger it, there is a small delay (1-2 seconds), and the engine will then miss once or twice.<p>: : I started to wonder if some sensor might be a little loose, but what?<p>: : If anyone has had this behaviour in their E34, and has a fix, I'd like to hear about it.<p>: : TIA. Paul.<p><br>: Further to this, I got an inspection II done today, and mentioned the problem to the mechanic.<p>: The diagnostics came up with an error 29 - Road speed signal. The mechanic said the sensor is in the diff, but he had to get some more info about the type of problems associated with it.<p>: Is this likely to have any significance with respect to the engine misses?<p>: Paul.<p>

Jon Brush
12-17-1998, 01:20 PM
This is *exactly* my problem to the letter, except no error message has shown up.Several mechanics have tried but nothing has been found wrong.<br> Please do post any solution which works, as Andy says! Hope you can help the rest of us with this problem. I will be in your debt!<br>TIA, Jon <br>: : I am certain this has been discussed before, so apologies up front, but...<p>: : I get an occasional engine "miss". It will only occur on a light throttle (never under load), and can be triggered by going over a bump. If a bump does trigger it, there is a small delay (1-2 seconds), and the engine will then miss once or twice.<p>: : I started to wonder if some sensor might be a little loose, but what?<p>: : If anyone has had this behaviour in their E34, and has a fix, I'd like to hear about it.<p>: : TIA. Paul.<p><br>: Further to this, I got an inspection II done today, and mentioned the problem to the mechanic.<p>: The diagnostics came up with an error 29 - Road speed signal. The mechanic said the sensor is in the diff, but he had to get some more info about the type of problems associated with it.<p>: Is this likely to have any significance with respect to the engine misses?<p>: Paul.<p>

Shawn Anderson
12-17-1998, 01:45 PM
<i>: : I am certain this has been discussed before, so apologies up front, but...<p>: : I get an occasional engine "miss". It will only occur on a light throttle (never under load), and can be triggered by going over a bump. If a bump does trigger it, there is a small delay (1-2 seconds), and the engine will then miss once or twice.<p>: : I started to wonder if some sensor might be a little loose, but what?<p>: : If anyone has had this behaviour in their E34, and has a fix, I'd like to hear about it.<p>: : TIA. Paul.<p><br>: Further to this, I got an inspection II done today, and mentioned the problem to the mechanic.<p>: The diagnostics came up with an error 29 - Road speed signal. The mechanic said the sensor is in the diff, but he had to get some more info about the type of problems associated with it.<p>: Is this likely to have any significance with respect to the engine misses?<p>: Paul.<p></i><p>Just to add a little something to this: I had a malfunctioning speed sensor in my rear differential. It would work sometimes and not others. However, it made no impact on how the car ran. <p>Shawn Anderson<br>1990 535i, 5 speed, 160K miles

Jon Brush
12-18-1998, 01:36 PM
FWIW: After I noticed the 1-2 sec pause between the bump and the "miss" (thanks Paul H for your observations), I began to think about what type of intermittent fault might be responsible. Without knowing much about the systems, it seems to me that a fuel delivery fault rather than a spark fault would be likely. It seems that a spark fault would be more "immediate" while a fuel fault, say in the fuel pump relay, etc., might take a sec or 2 to "reach" the engine and cause the miss. Also, this might account for the feeling that the miss occurs only on light load, as that would be when the fuel is "just barely" being delivered by the injection nozzles. Perhaps the fault does occur under heavier throttle conditions but we don't notice it because there is more total fuel being delivered at that time and the "micro" fuel stoppage is "buried".<p> Does this make sense to anyone else? Where would you think of looking first? Paul, does your mechanic have any ideas yet?<p>Jon '92 535i 5sp<br>Way too much time to think......;^)

Andy Peavy
12-18-1998, 01:59 PM
<i>: FWIW: After I noticed the 1-2 sec pause between the bump and the "miss" (thanks Paul H for your observations), I began to think about what type of intermittent fault might be responsible. Without knowing much about the systems, it seems to me that a fuel delivery fault rather than a spark fault would be likely. It seems that a spark fault would be more "immediate" while a fuel fault, say in the fuel pump relay, etc., might take a sec or 2 to "reach" the engine and cause the miss. Also, this might account for the feeling that the miss occurs only on light load, as that would be when the fuel is "just barely" being delivered by the injection nozzles. Perhaps the fault does occur under heavier throttle conditions but we don't notice it because there is more total fuel being delivered at that time and the "micro" fuel stoppage is "buried".<br></i><p>I'm thinking that the fuel rail is pressurized and would be supplying the injectors with more than enough fuel for a part-throttle "lack-of-fuel" problem.<p>Of course, I'm guessing...<p>Andy Peavy<br>91 535i<br>email: apeavy@yahoo.com

Jon Brush
12-18-1998, 04:52 PM
Andy: Doh....That makes sense...any other thoughts?<p>Jon '92 535i 5sp<br>

Paul H
12-19-1998, 07:59 PM
<i>: FWIW: After I noticed the 1-2 sec pause between the bump and the "miss" (thanks Paul H for your observations), I began to think about what type of intermittent fault might be responsible. <br></i><p>Here are my further thoughts. At my recent Insp II, my mechanic commented that I had electronic throttle and ASC controls (i.e. not actuated by cable). I got to wondering if some intermittent problem with the road speed sensor might cause a temporary confusion with the ASC, causing it to come into play unnecessarily.<p>I'm going to get the road speed sensor error further diagnosed by BMW, some time after New Years Day, so I'll post any interesting info that might arise.<p>Paul.<br>

Paul H
12-21-1998, 06:03 AM
<i>:<br>: Here are my further thoughts. At my recent Insp II, my mechanic commented that I had electronic throttle and ASC controls (i.e. not actuated by cable). I got to wondering if some intermittent problem with the road speed sensor might cause a temporary confusion with the ASC, causing it to come into play unnecessarily.<p></i><p>Thinking things through further (and I am a physiotherapist, not a mechanic), since the problem usually occurs at a light throttle, which should imply a higher degree of manifold vacuum, it could be that there is some problem with vacuum leakage, allowing unwanted and unmetered air into the system. <p>This problem could perhaps be intermittent, such as a dodgy vac hose connection, or a somesuch. I notice that many hoses are clamped with those cruddy crimp-on things, and I've replaced a couple around the engine bay which are loose (such as the hoses on the power steering fluid reservoir).<p>Anyway, responses anyone? Especially from those with experience in engine management systems???<p>Paul.<br>

Jay
12-21-1998, 11:23 PM
<i>: :<br>: : Here are my further thoughts. At my recent Insp II, my mechanic commented that I had electronic throttle and ASC controls (i.e. not actuated by cable). I got to wondering if some intermittent problem with the road speed sensor might cause a temporary confusion with the ASC, causing it to come into play unnecessarily.<p><br>: Thinking things through further (and I am a physiotherapist, not a mechanic), since the problem usually occurs at a light throttle, which should imply a higher degree of manifold vacuum, it could be that there is some problem with vacuum leakage, allowing unwanted and unmetered air into the system. <p>: This problem could perhaps be intermittent, such as a dodgy vac hose connection, or a somesuch. I notice that many hoses are clamped with those cruddy crimp-on things, and I've replaced a couple around the engine bay which are loose (such as the hoses on the power steering fluid reservoir).<p>: Anyway, responses anyone? Especially from those with experience in engine management systems???<p>: Paul.<p></i>I think you're on the right track about a vacuum leak because the problem occurs at light throttle. Now if the idle speed starts to get affected then the likelihood increases that it's indeed a vac problem.<p>I've had hose problems too. My trans fluid hose had to be replaced at 30k miles, and most of the cooling system hoses by 60k.<p>Jay<br>90 535

Jon Brush
12-22-1998, 08:25 AM
Paul: Good luck! Let us know how it turns out. TIA<br>Jon<br>'92 535i 5sp 67.5Kmi<p><br>

Jim L.
01-01-1999, 11:18 PM
<br>: : :<br>: : : Here are my further thoughts. At my recent Insp II, my mechanic commented that I had electronic throttle and ASC controls (i.e. not actuated by cable). I got to wondering if some intermittent problem with the road speed sensor might cause a temporary confusion with the ASC, causing it to come into play unnecessarily.<p>: <br>: : Thinking things through further (and I am a physiotherapist, not a mechanic), since the problem usually occurs at a light throttle, which should imply a higher degree of manifold vacuum, it could be that there is some problem with vacuum leakage, allowing unwanted and unmetered air into the system. <p>: : This problem could perhaps be intermittent, such as a dodgy vac hose connection, or a somesuch. I notice that many hoses are clamped with those cruddy crimp-on things, and I've replaced a couple around the engine bay which are loose (such as the hoses on the power steering fluid reservoir).<p>: : Anyway, responses anyone? Especially from those with experience in engine management systems???<p>: : Paul.<p>: I think you're on the right track about a vacuum leak because the problem occurs at light throttle. Now if the idle speed starts to get affected then the likelihood increases that it's indeed a vac problem.<p>: I've had hose problems too. My trans fluid hose had to be replaced at 30k miles, and most of the cooling system hoses by 60k.<p>: Jay<br>: 90 535<p>I have had exactly the same symptoms for several years in my 91 5 speed 535 with ASC. Others have noticed it, but no one has been able to diagnose or fix it. I also thought it might be ASC related (it doesn't seem to do it with the ASC switched off), but when the symptoms occur the ASC light never comes on. My car has plus 1 (16 inch) wheels, so it might be confusing the sensors. FYI, there is a service bulletin (no. 12 09 91 (3413) dated December 91 that describes this problem and suggests an updated control unit as the fix. However, my car has the newer control unit and still has the problem, and the bulletin only seems to apply to 91 model E34s. If you find a solution I'd love to hear about it. Good luck.<p>Jim (91 535)


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