Intermittent Complete Loss of Power

[theshadow92]

Usually happens around the lower RPM range. When it happens, I usually go WOT and the power usually comes back. Lousy idle as well. What gives?

[ethirtydavid]

Give us more information with the circumstances when it dies. acceleration? hard acceleration? idle?
when you say loss of power, do you mean loss of electrical power and the car shuts off? or do you mean the engine feels weaker?

[theshadow92]

Sorry for being so vague! Car never shuts off but it experiences a tremendous loss of power. Power is almost non-existent. This never happens during hard acceleration.

[ethirtydavid]

read through this guys account and see if your situation is similar, or if the idle and power loss with your car are being caused by an alternative issue.

http://tkltian.wordpress.com/2011/08/01/e30-intermittent-power-loss-problem-log/

[theshadow92]

My situation does sound similar however I was under the impression that oxygen sensors throw codes. But I would be more than happy to unplug mine if you could show me where they are located exactly on an E36 M42. Thanks!!

[ethirtydavid]

Ah, and this whole time I assumed you were talking about an e30..
Guess we should have started with your car and engine - anyone chime in, do m42 have oxygen sensors?

[theshadow92]

92-95 M42's have only one O2 sensor and its located just before the cats. Problem is, you have to jack up the car to get access to it. Is it OK to unplug it for extended periods of time?

[roguetoaster]

On the E30 the O2 plug is on the passenger side at the very back of the engine bay mounted on the side of the chassis (and is a round connector just like the AFM), perhaps the E36 is similar. Whatever the case the plug will be near the exhaust manifold.

Does the cars idle fluctuate instead of sticking at an RPM too low for proper idling, if so my money is on vacuum leak. But an AFM or CTS failure is also a strong possibility. Give us more info on the poor operation, when it comes in, if the car needs to be hot or cold, and if the car is having trouble starting.

[theshadow92]

I think I found the O2 plug on the E36 and it was underneath near the transmission.
Very little to none idle fluctuation. No trouble starting. Usually needs to warm up a bit. The problem happens about 70% of the time but when I unplug the AMF the problem is there 100% of the time so I'm leaning towards a bad AMF. Best way to test it? Or does anybody want a video?

[ethirtydavid]

a bad AMF??

[roguetoaster]

I think I found the O2 plug on the E36 and it was underneath near the transmission.
Very little to none idle fluctuation. No trouble starting. Usually needs to warm up a bit. The problem happens about 70% of the time but when I unplug the AMF the problem is there 100% of the time so I'm leaning towards a bad AMF. Best way to test it? Or does anybody want a video?

Read this on testing the AFM http://m42club.com/forums/showthread.php?t=5427

Sounds like you may have a dead spot in the carbon track. But the test will reveal more.

[theshadow92]

I've heard the only TRUE way of testing a AFM is with an oscilloscope. Any other likely culprits I should be looking at?

[roguetoaster]

Like we said above, the O2 sensor, and the AFM are the most likely electronic faults. Additionally, the cam & crank sensors could be experiencing some odd issue, but it probably wouldn't be at just low RPM. Outside of that maybe a faulty TPS that thinks it's at WOT all the time, but this is not overly likely.

Probably testing the AFM with an oscilloscope would be the most effective measure, but most of us don't have that. Of course you would probably end up dismayed at its poor performance from a purely electronic standpoint.

Other possibilities include a vacuum leak (likely) or a fuel pressure/delivery issue (not likely).

Does the car stutter after you let off of the throttle during these periods of poor performance? When my O2 sensor was having issues (coding infrequently) it caused poor initial acceleration, stuttered occasionally on throttle lift to idle, and performed fine at or near WOT.

[ScottySbk]

Wanna bring this back to life as i’m having the same issue but with my e30, someone suggested someone’s account to read off of but the link doesn’t work anymore. Let me give the exact experiences i’m having, it’ll start it definitely took longer to start just by a second or so because normally she’d start right up, but the idle was quite rough. Drove it and it never stalled though it sounded like it wanted to, at lower RPM’s I’d have no power when accelerating but once at higher speeds or WOT it’ll drive and run good.