M50 with idle/power issues

[18rabbit]

Sup R3v,

So I bought this e30 m50 late last year and have been slowly fixing it up. Car had lots of goodies installed. The swap though, was done so shoddily that I've basically had to "re-swap" the car, that being said, I'm in the finishing stages and have run the car for a couple hundred miles. Lately the CEL has been on and I've been experiencing idle and power issues. Idle sometime surges, and car misfires or breaks up at random times but mostly when warm. I've also seen the CEL come on and go off multiple times in say a 30 minute drive.

Here is a breakdown of symptoms:

M50 VANOS engine
Only CEL code: 1221

O2 sensor newish
Cluster coolant temp sensor (brown top) is new
Crank sensor is new
Knock sensors are new
spark plugs are new
coil boots are new
Valve cover gasket, intake boot, and all vacuum lines are new

Smoked tested (with home tester) no vacuum leaks
Sprayed carb cleaner, no detection of vacuum leaks
ICV hums at idle and was cleaned with brake cleaner
MAF just cleaned with CRC MAF cleaner

I'm tempted to buy a new O2 sensor but I'd rather do some deductive reasoning before throwing parts at this problem. Let me know what you think.

[18rabbit]

So I unplugged the battery for the weekend while I was away. Cam back tonight, hooked up battery. Took car for a spin CEL came on then off then on then off... in the course of a 5 mile drive. Got back and parked it and now its throwing engine code 1222 so now I'm definitely thinking this is an 02 sensor issue.

[328ijunkie]

Vac leaks/tune. 1222 doesnt mean O2 sensor itself.

[18rabbit]

What does it mean when I unplug the o2 sensor or unscrew the oil cap and the idle returns to normal?

I can also unplug the maf now and rpm surges a little but then finds idle. When I unplug the ICV the car idle goes nuts. I feel that there is a misfire somewhere. Would a misfire, say a bad coil, cause the o2 code?

What are the next steps I should take to get this thing back in order?

[328ijunkie]

Verify Vac leaks not present. Check what chip is in there.

[18rabbit]

Verify Vac leaks not present. Check what chip is in there.

The chip is the appropriate TMS chip for an m50 with s50 cams and lightweight flywheel, I verified this when I had the car broken down over the winter.

Today I used my bee smoker to check for vacuum leaks again and didn't see any leaks, then I put my mouth on the intake boot and held throttle open and blew as hard as I could and couldn't hear any air leaks LOL. One thing I did try was using the carb cleaner spray on an open vacuum leak. So i pulled the crank case valve (remember this is an obd1 m50) and sprayed the carb cleaner at the opening and got no response from the engine, shouldn't the engine rev?

[dunebuggyjay]

Did you ever figure this out?

[18rabbit]

Did you ever figure this out?

Negative ghost rider, Car has been in pieces, trying to figure out what flywheel is installed. I have a new 02 sensor and rebuilt injectors to install so hopefully next week we can see if shes running again. I also have a MAF from a friend that I will try to swap in. If they don't do it I'm gonna try the engine coolant temp sensor.

[18rabbit]

So I put everything back together with new injector filters/o-rings and a new o2 sensor. Car threw CEL until I gave it an ole Italian tune up and its been perfect ever since.