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ChrisDT 15th July 2017 11:04 AM

E36 328i Sport - Erratic Idle
Hi All, apologies for what may be a done to death first post but search didn't bring anything specific up:

I have a 1998 E36 328i Sport and recently (last 200 miles) it has started to hunt when I am at a junction and on occasion stall. Very annoying - so after a bit of internet doctoring it pointed at either a MAF or a Cam Sensor. I have unplugged the MAF and it doesn't make any difference to how the car runs apart from when I plug the MAF back in it triggers the car to hunt quickly but I put this down to the introduction of the MAF again.
I have also changed the Cam sensor and although it appeared to run a little smoother within 30 seconds or so it started to hunt again on tick over - but no stalling, yet. When the car is shut down (by the key) there is a suction noise from near the MAF, I don't have another car to compare it to so not sure if this is normal. Haven't looked at the CCV yet as I only started reading about this today and i'm not with the car until this evening. It may be the air intake boot but that appears to look ok on the surface and I sprayed bubbles near it yesterday and no signs of a leak.

Plugs appeared ok, but I have a spare set of NGKR kicking about I could change them with but it's not lumpy it's just erratic like it's getting starved.

Any advice would be greatly appreciated at this point as i'm chasing my tail.

E46CoupeM3 15th July 2017 11:41 AM

Yo need INPA and to run proper diagnostics on the car.

Sounds like an air leak though

ChrisDT 15th July 2017 12:15 PM

Yeah, I'm going to change the intake boot next and see if that cures it - worth a go!

E46CoupeM3 15th July 2017 12:24 PM

Better to look at the boot for splits and only change if required. Throwing money at parts you don't need is a waste. Better spent where the problem is.

ChrisDT 15th July 2017 12:34 PM

Agreed, but I can borrow one from someone - Going to Vanity tomorrow so may be someone kind enough to assist with a trial fit if required. Also been advised to check the crank case breather hose.

E46CoupeM3 15th July 2017 12:40 PM

Last time I priced one it was 45 for the non-AST version. Splits are easily seen and usually in the convoluted section or under the jubilee clips.

Just changing randomly, even if free you run the risk of fixing it by accidentally disturbing something else and still spending the money and being no wiser / fault reoccurring later

But hey you spends your money and makes your choice.

If you hooked it up to INPA you would see if air through the ICV + air through MAF which IIRC it should at idle unless you have an air leak behind the MAF

ChrisDT 15th July 2017 12:46 PM

Good point, annoyingly I have INPA but my laptop won't run it so it's not that handy! I'll get it plugged in and see what happens I think. Do a visual check on the hoses again and see if I missed anything.

alpina527 15th July 2017 12:55 PM

I wouldn't run the risk of borrowing someone else's boot. Disturbing could easily damage it.

If yours shows any sign of perishing just buy a new one. They usually split along the folds or on the Icv adapter joint.

Are you running an aftermarket filter that stretches the boot?

E46CoupeM3 15th July 2017 01:02 PM


Originally Posted by ChrisDT (Post 2360382)
Good point, annoyingly I have INPA but my laptop won't run it so it's not that handy! I'll get it plugged in and see what happens I think. Do a visual check on the hoses again and see if I missed anything.

Don't spray flammable WD40 all over the boots to hear if the idle picks up indicating the combustible stuff has been drawn in through an air leak

ChrisDT 18th July 2017 03:46 PM

Hi, sorry for the late reply - no it's all standard so no extra pressure on it. Ordered an intake boot so i'll try that.

I also removed the engine oil cap when the car was running as per advice and it didn't make any difference to the erratic idle which suggests an air leak somewhere! Just to find it!

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