M52 Odd Idle/CEL

[ArtClassShank]

Hey all, back with another troubleshooting puzzle.

My M52B28 E30 is having a bit of an idling problem. It never dies or stalls, but it idles high at around 1100RPM, and surges and moves after coming to a stop.

If I start it cold and let it sit idling, it'll stay rock solid at 900. But once warm and actually moving, it starts to idle at 1100. The other thing that effects idle is sitting still for 30+ seconds. After coming to a stop and sitting for 30 seconds, it'll throw on a 1221 CEL code, and the idle will drop down to 900.

The odd thing is I can get rid of the CEL seconds later if I shift at 3K+ RPM.

Here's a video of the problem, this is after a spirited 30 minute drive.

http://www.youtube.com/watch?v=eu1XPlqfGx8

It does have a TRM chip and the following mods:

• 3.5" Euro E36 M3 HFM
  OBD1 conversion
  Upgraded injectors
  3.5" K&N intake
  Supersprint long tube headers

So far I've looked around for an intake leak and cleaned my ICV. I've often heard O2 sensor codes are almost never an O2 sensor on these motors, so I haven't replaced that.

Anyone have any ideas or similar experiences?

My next move might be to get a new ICV, but thats expensive.


Thanks

[ParsedOut]

The 1221 code is an indication that you're either running really lean or really rich (or bad O2, but as you mentioned that is less likely).

Clean your MAF with MAF specific cleaner.
You already mentioned vacuum leaks, I would recommend completely disassembling all of the intake hoses (PCV, ICV, evap, intake boot, etc) and inspect them on the work bench for cracks or leaks. If nothing is found, put it all back together and have a shop smoke test it, shouldn't cost much and can save you hours of headaches. Based on your idle issues, I'm heavily leaning towards an inconspicuous vacuum leak.
If it passes the smoke test, then move onto fuel pressure check.
If it passes that, I'd take a look at your fuel injectors and have them cleaned/flow tested.
Then you're into DME/sensor territory, but I'd be willing to bet you'll figure out the issue by that point.

[ArtClassShank]

The 1221 code is an indication that you're either running really lean or really rich (or bad O2, but as you mentioned that is less likely).

Clean your MAF with MAF specific cleaner.
You already mentioned vacuum leaks, I would recommend completely disassembling all of the intake hoses (PCV, ICV, evap, intake boot, etc) and inspect them on the work bench for cracks or leaks. If nothing is found, put it all back together and have a shop smoke test it, shouldn't cost much and can save you hours of headaches. Based on your idle issues, I'm heavily leaning towards an inconspicuous vacuum leak.
If it passes the smoke test, then move onto fuel pressure check.
If it passes that, I'd take a look at your fuel injectors and have them cleaned/flow tested.
Then you're into DME/sensor territory, but I'd be willing to bet you'll figure out the issue by that point.

Cleaned the MAF already, first thing I thought of.

I got a quote for a smoke test, $200. Seems kinda expensive, but that seems like the norm for my area.

I'll see if I can get it done cheaper. Hopefully it is a vacuum leak, would be a nice easy fix.

Thanks

[e30forlife]

Crazy thing for me too. I replaced all 02 sensors, replaced ICV "known working", replaced CCV...Turned out it was my Fuel Pressure Regulator...I took the vacuum line off of it and fuel was dumping out of it..This was brand new part also..After I replaced that my car was perfect.

My setup is m52b28 running m50 manifold..I am using a m50 fuel rail for this setup also.

[ArtClassShank]

Crazy thing for me too. I replaced all 02 sensors, replaced ICV "known working", replaced CCV...Turned out it was my Fuel Pressure Regulator...I took the vacuum line off of it and fuel was dumping out of it..This was brand new part also..After I replaced that my car was perfect.

My setup is m52b28 running m50 manifold..I am using a m50 fuel rail for this setup also.

Is the FPR in the engine bay? Or down near the filter under the car?

[e30austin]

FPR is located on fuel rail. You'll have to remove the fuel rail to get it out.

[ParsedOut]

FPR is located on fuel rail. You'll have to remove the fuel rail to get it out.

Depends if he's running an M50 NV or M50TU fuel rail if I'm not mistaken.

[RobertK]

Depends if he's running an M50 NV or M50TU fuel rail if I'm not mistaken.

No, its the same for both.

If you can't afford a smoke test then try the brake cleaner / carb cleaner test. Also try disconnecting the O2 and see if that makes any difference.

[ParsedOut]

No, its the same for both.

If you can't afford a smoke test then try the brake cleaner / carb cleaner test. Also try disconnecting the O2 and see if that makes any difference.

Oh yeah, I'm confusing M50 vs M52.

[Pipes]

Hey OP, did you figure this out? I have exactly the same setup as you and have the same issue, although mine wants to "idle" at 2800. Car runs great at WOT but has a weird part-throttle hesitation and the idle that behaves same as yours....

[techno550]

1221 is the code for Primary O2 sensor.
1222 is Lambda control 1.
1222 is too lean or too rich for too long. 1221 is bad (or no) signal, and can be heater circuit related.

More trouble codes can be found here:

http://www.trmtuning.com/?p=2492

Though a sufficiently large vacuum leak can throw it. Vacuum leak will also yield a higher warm idle since it is the leak controlling the idle and not the ICV.

Pressure test or smoke test is the best way to find the leaks. You will be surprised what can leak on the older cars. The common leak points on a NA car, especially a swap car, is the charcoal canister port on the throttle body. Often that system is compromised or not connected properly, so a relevant test, assuming its not just a gaping hole like we often find, is to remove that hose and cap it.
The brake booster can also be a source of a vacuum leak. Sometimes wiggling something that hasn't been wiggled since 1987 has undesired effects.

more on leak testing: http://www.trmtuning.com/?p=2424

[TeXJ]

Wonder if this was ever fixed...