Excruciating miss that I can't resolve !! - BMW Forum - BimmerWerkz.com
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#1 (permalink) Old 10-21-2013, 06:55 PM
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Exclamation Excruciating miss that I can't resolve !!

No idea what to try next....

'92 525i, auto trans, M50, non-VANOS, 243,000+ (still usually 22-23mpg)

Experiencing a horrible miss/stumbling pattern and I just can't figure it out.

Started with an intermittent CEL back in the beginning of August. Code was O2 sensor. Noticed it had a slight miss every now and then, and mpg was dropping slightly over the next two weeks. Installed new O2 sensor. CEL has never reappeared, and no codes are present.

But the miss/stumbling has gotten absolutely horrible. I have A LOT of cash wrapped up in this already, and I'll NOT quit now.

Following is a list of what I've changed/repaired, etc.:

Changed:

•ECM
•MAF
•Spark plugs
•Coil packs/boots
•Injectors
•Fuel pressure regulator
•Fuel filter
•Crank sensor
•Cam sensor
•TPS
•Feed/return fuel hoses (at the rail)
•Two vacuum hoses from PCV


Checked and verified OK:

•Fuel pump electrical and system pressure
•ICV
•Cylinder compression (all within acceptable ranges)
•All sensor electrical plugs
•All other appropriate electrical for fuel/ignition system


Vehicle starts fine, idles and drives great, until it starts to warm up.....then the idle becomes erratic and the missing starts. Driving at highway speeds (above 60mph) and it's basically smooth, even when stomping it to the floor with the resulting gear range kick-down. City driving is nothing but stumbling, sputtering, chugging....it just seems like symptoms of intermittent spark and/or fuel. If I sit in the driveway with the parking brake on, my foot on the brake, put it in drive or reverse and press on the gas, it misses so badly it shakes the whole vehicle and won't get above 2000rpm.

ANY / ALL ideas are appreciated. Thanks.
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#2 (permalink) Old 10-22-2013, 09:35 AM
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No vacuum leaks. Already removed, checked, replaced every vacuum hose, and even did the starting fluid spray test at various rpms around said hoses, throttle body, intake manifold, etc. Same result.

Coil pack wiring and everything else in the wiring harness next to the fuel rail is like new, not brittle or deteriorating. Ground wire is fine.

Just this am: changed the ICV and the ATS....what's a few more bucks, right?

No difference, same result.

I hate to think about it, but could the timing chains be failing?
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#3 (permalink) Old 10-22-2013, 06:46 PM
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Quote:
Originally Posted by PA 525i View Post
I hate to think about it, but could the timing chains be failing?
The timing chain wont fail, its the tension that can wear out. Its a hydraulic tensior and they have failed in the past.

Not sure what else could be causing it to be honest. Youve gone through the whole run down for a miss.


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#4 (permalink) Old 11-14-2013, 06:26 PM
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do you have scan tool
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#5 (permalink) Old 11-14-2013, 10:38 PM
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Could the torque converter be locking up??
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#6 (permalink) Old 11-17-2013, 12:30 PM
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I know its a obd1, live data could help, specialy when problen is in idle
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#7 (permalink) Old 11-23-2013, 03:42 AM
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Have you cleaned and checked the intake? A smoke test is easy and informational..
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