530 with M60 idle problems ongoing saga.

[paps49]

Newb here, thought Id jump right in.

Recently purchased an E34 530i '95 and love it to bits but the bitch doesnt want to idle when cold. It tries unsuccessfully to idle at about 600 rpm which is its hot idle speed, I think still too low for an auto even warm. I have been through the Bentley and the forums and got a lot of useful info but have ended up in a weird place.

The PO changed the O2 sensors less than 5k ago.

In order I have......

Removed the intake system and cleaned it, the throttle body and ICV checked for leaks etc - some minor improvement for a short time.
Replaced the ICV _ no change.
Ditto the Temp sensor and the air sensor separately - no change.

Now is the weird part, on Sunday in frustration I unplugged the MAF - problem solvered. No engine check light, idles great cold, a little lumpy warm but acceptable and drives fine.

How is this possible? I can understand the cold idle improvement if the MAF is the culprit but why doent it run like **** with no MAF and hot?

[shogun]

did you check if the oxy sensors are mixed up (wrong connections under the car), oxy sensor plugs cylinder row 1 connected to 2 and vice versa?
I once mixed that up when I changed the oxy sensors, so I connected the oxy sensor of right bank to the plug for the left bank exhaust and vice versa on my M70 V12 engine. Idle was terrible.
Both wirings and plugs coming from the engine are almost side by side under the car and mixing them up is possible.

[paps49]

Thanks Shogun, I will look into that.

[paps49]

Todays thought, I am a courier so way too much time to think/drift off.

I have come across various references to the ECU "adjusting" for engine wear, age, leaks etc and it can all build up over time. One recommendation was to disconnect the battery then short the ICU for 10 mins by connecting the + - battery cables together ( being careful not to short the not connected battery). I wish now I had done this first, but is it conceivable that the MAF has been going west/getting covered in crap for so long that the ECU has compensated for it already? Just couldnt fix the cold Idle?

[632 Regal]

Your cold idle problem is the intake gaskets and possibly the valley pan gasket. Careful with the intake gaskets they sometimes tend to not end up where designed to go, slow and steady so it don't fold over in the rear of the engine area.

[paps49]

Your cold idle problem is the intake gaskets and possibly the valley pan gasket. Careful with the intake gaskets they sometimes tend to not end up where designed to go, slow and steady so it don't fold over in the rear of the engine area.

Thanks Regal, I'll check that out.

Sadly that will have to wait. The radiator shat itself a few days ago, had to tow it home. Went to replace the radiator today and of course the w/pump is history too, cant get one till Tuesday.

[genphreak]

When you removed the intake did you replace the check valve cover? That is the common culprit on an M60. Here's some more info in a how to (http://blog.bavauto.com/10769/diy-video-–-bmw-v8-m60-m62-crankcase-ventilation-check-valve-cover-how-to-replace/).

[Bill R.]

If you're cold idle speed is the same as warm it sounds like a bad coolant temp sensor sending the wrong info to the dme. Check your coolant temp sensor.