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Old 01-20-2020, 06:56 PM
shadybeings shadybeings is offline
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Location: Central FL
 
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Mein Auto: E39 540i, E34 540i, E36M3
95 540iA bogs with throttle

I just bought a 540iA, not much info on the car. I got it cheap cause it runs like absolute garbage in its current state.

When I give it gas the car bogs down. I found out if I sit there flooring it it will start backfiring and eventually will catch and rev all the way to 6500rpm.

I'm assuming the problem comes from either a bad throttle body or MAF sensor. My assumption is that when I press the gas pedal the fuel is pumping properly but the throttle isn't opening up so now the cylinders are flooding due to oxygen starvation. There are moments where it will run perfectly but basically I had to drive it around just at idle.

Is this a common problem that people have an easy answer to? If not I'll just try to get my hands on a new throttle body and MAF sensor.
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  #2  
Old 01-21-2020, 06:30 PM
Mr._Graybeard Mr._Graybeard is offline
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Mein Auto: '95 540i, '95 525it
Try the "stomp test" to see if you get any codes. I'd be checking the throttle position sensor. That can produce acceleration problems and affect the operation of the transmission as well.

The bane of the M60 is vacuum leaks. Do you have a vacuum gauge? I'd measure intake manifold vacuum to see if it's within spec (17 hg/in or better). As a WAG, I'd suspect your engine is running too lean rather than too rich. Throttle position sensors have a wide-open position that sends a full-rich signal to engine management. That may be why your engine responds when you open it up all the way.
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Old 01-23-2020, 09:41 AM
Mr._Graybeard Mr._Graybeard is offline
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Mein Auto: '95 540i, '95 525it
I've been reminded that the throttle position sensor on the M60 does not have an full-throttle switch like earlier engines, so full throttle would not send a supplementary signal to the ECU, just the full 5-volt signal voltage. Still, TPS is worth checking, but vacuum leaks are more likely.
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  #4  
Old 01-28-2020, 09:41 AM
shadybeings shadybeings is offline
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Mein Auto: E39 540i, E34 540i, E36M3
I'm embarrassed to show how simple the fix was. You are correct it was vacuum but I should've seen that from the start. The piping behind the MAF was broken, didn't immediately trigger for me that since it's after the MAF it would be a problem.

Some tape made it run right now. Will get new piping over the weekend and get some fluids and I'll have my new daily! Tired of driving my manual 540i loll
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