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Topic Review (Newest First)

  • 07-08-2008, 09:48 PM

    Replace the air boot.

  • 06-27-2008, 10:41 AM

    Re: E28 - Engine Stall @ 1500 RPM or medium cruise spd

    if it is popping back through the intake, that is a lean condition. If the engine starts reliably, then the speed and reference sensors are OK. If you start messing with them, you may as well buy new ones because the harness plugs will crumble. My money is on a vacuum leak. Does the front crank seal leak oil?
  • 06-25-2008, 09:04 PM

    Re: Ref & Spd Sensors & timing

    chug chug - no change I re-checked the crankshaft sensor and can't see how it would disconnect.
  • 06-25-2008, 08:37 PM

    Re: Ref & Spd Sensors & timing

    OK, I finally got the resistance checked on the speed sensors. It is interesting there are two sensors that tie into the transmission housing. I removed them from below and cleaned then off, and then checked, and they were both 1,000 ohms. I cleaned the connections, lightly sanded them with fine black paper, and put some electrical grease on the connectors before attaching. I haven't tested it yet, but one of the connectors had the locking wire a little out of the position, and maybe I am up and running. I am not finding the speed sensors from rockauto, and not sure where to find a replacement. My main question at this point is that I can't find the top plug on the crankshaft sensor. It seems to tie into the main computer plug. Ideas?
  • 06-01-2008, 11:09 AM

    Re: Ref & Spd Sensors & timing

    There may be some dirt and a little grease, but mostly iron particles clinging to the mag head of the sensor. Enough of those iron fuzzies could bridge the gap reducing or nullifying pulse signal.

    15 inches vacuum is a bit on the low side...and I assume the needle is steady at idle which is good. Have you removed all rubber and checked for cracks? Have you tightened up the oil pan?
  • 05-31-2008, 09:18 PM

    Re: Ref & Spd Sensors & timing

    I will check the sensor resistance and get some replacements in play. My son's 735 is waiting the crank sensor part stranded in our drive.

    I don't have any grinding when starting, and saw a good view of the flywheel about 4 years ago during a clutch job, and don't recall any missing teeth. Is there a chance the sensor could get grease on it and not work reliably?

    A local car call in show was also talking about the lean condition, and thought there might be an air leak. My vacuum is running 15 lbs, and I saw another forum indicating this is normal. I would assume this means there isn't air leak after the AFS.

    Thanks again for your input and ideas. This is a great forum, and I will look forward to sharing ideas I have learned also.
  • 05-31-2008, 12:14 PM

    Ref & Spd Sensors & timing


    If you have an ohmmeter, carefully disconnect the sensors (one at a time) and check to verify ohms range from 960 to 1050. The connectors are probably brittle and baked. If ohms are higher than 1050 or have more than 100k miles, replace them as routine maintenance. When the ref sensor fails, you will have a no-start.

    One other question: Has the starter motor ever made a grinding noise when starting? If so, you may have teeth missing on the fly wheel. The teeth are the triggers for the speed sensor, which in turn signals the ECU for proper timing advance (I'm focusing on your backfire issue...either an ultra lean mixture which I doubt or timing).
  • 05-31-2008, 08:24 AM

    Re: E28 - Engine Stall @ 1500 RPM or medium cruise spd

    I have not replaced the speed and reference sensors in the last 130,000 miles. I will look into the slipped chain and valve adjustment. A dealer mechanic contact had also mentioned the possibility of a worn cam lobe and that it would be worth taking the valve cover off to inspect.

    Again, I emphasize that the performance is good at low idle, and good at a harder high idle, but missing in the middle, when the car would be leveled out, or getting the best gas milage performance for that particular gear.

    Thanks so much for the ideas, and hopefully we can get back on the road again.
  • 05-31-2008, 12:28 AM

    Re: E28 - Engine Stall @ 1500 RPM or medium cruise spd

    Pull valve cover and see if the cam gear slipped a couple of teeth on the chain due to excess chain slack and worn gear teeth and chain runner. Use the Bentley manual for the procedure. With the backfiring, you may have blown the new AFM. While you have the valve cover off, adjust the valves. Have you replaced the speed and reference sensors within the past 60000 miles?
  • 05-29-2008, 09:15 PM

    E28 - Engine Stall @ 1500 RPM or medium cruise spd

    I am having trouble with my 85 535 stalling hard, backfiring, and jerking the car (like someone grabbing you by the shoulders and shaking forward and backward). It happens at about 1500 RPM in 1st and 2nd (manual trans) and at about 2200 RPM in 3rd. If I push hard through the rough spot, the car will accelorate and have full power, and it will also idle and run at low RPM w/out stalling. I have changed fuel filter, MAF, Throttle switch, O2, cap/rotor, wires, plugs and a partridge and a pair tree. The only thing I haven't changed is the Fuel Pressure regulator. There seems to be strong vacuum, with a noticable decrease in idle when I pull the dipstick. There are numerous exhaust leaks down under, and there are noticable clouds of smoke coming up from the rear of the engine when I run Sea Foam into a vacuum line. (expect smoke with Sea Foam, and it is supposed to clean out carbon deposits). The car is ringing in at 290,000 miles, and I haven't done anything to the intake or valve adjustments since 162 K where I bought the car. Ideas? This has been a great running car, but this one really has me stumped.

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