HELP with e85 annoying idle.

M

Michael85

New member
Ok so I have been lurking on here for over a year, I’ve tried to sign up a few times but it’s never worked...until today! So I will take that as a sign that one of you amazing people will hear my problem and instantly tell me the real issue!

I’ve owned my z4 with 98000 miles on the clock for about 2 years now. I love it, it’s a 3.0 m sport (b12 suspension upgrade because the msport dampers were shot and one spring had snapped (still passed an mot on these worryingly). roof motor went last year but this year I dragged it out and managed to bring it back to life and relocate it to the boot.

But the issue that really gets me is the idle. It’s just not rock steady. It will be between 690-720 and just blip between these with no set pattern! It never stalls, it always starts, it’s the same hot or cold. If you cruise you can still kind of notice it.

I have done as a course of action and because a car of this age just needs some bits and love.

Vanos seals upgrade: I had the rattle.
Intake boot: it split I replaced it.
Disa: old one shot new one is perfect.

Now I had a flat spot and a p0012 so I cleaned the intake solenoid and I replaced the exhaust one cause it was sticking even after cleaning. Flat spot sorted and she pulls better than ever.

MAF sensor: the one in the car has a slight crack in the grill housing and I was paranoid about it breaking loose and flying into the engine so got a Brand new OEM one Hella i believe?

Cam position sensors changed (did those tonight)

Plugs and coils all changed cause I got new boosh ones for a great price of the net.

Idle control valve is clean and isn’t sticking at all.

But still...still....the car idles with that slightly annoying, something not right blip. You can feel it slightly shake or shiver every few seconds.

I have sprayed carb cleaner everywhere to find a vac leak!

Is there something I am missing.

The reason I am asking in a new thread is because believe me I have searched all the others and the symptoms of the others are not the same as mine, it’s not a massive fluctuation like others have reported, it doesn’t stall, hot or cold it’s there.

I have got a magner flow exhaust cat back custom, wouldn’t have thought this would cause the issue though.
 
You can try getting someone with diagnostic software like DIS v57 or above to set the idle higher by up to 100rpm this might smooth out the idle, also try updating the cars spdata files as idle was an issue
 
You don’t seem to have mention the ccv which is known to get gunked up and cause idling issues. How much vacuum do you get if you remove the oil cap with engine running. Any oil in the inlet manifold at all?
 
Thank you both for the quick response. I will try and get a local bmw indie to have a look at the software at some point. The ccv was one of my I hope nots, it looks like a ball ache! Can it be cleaned assuming it’s not leaking or cracked that is, or is it worth just replacing? How much suction should you get when you remove the oil cap, I know that’s a hard thing to explain in words but if it’s meant to suck like a Dyson then I’d say no it doesn’t. I can easily remove the cap while running and the engine bogs and sounds horrible and returns to normal (all be it not perfect) when the caps put back.
 
It should be very light vacuum (a good test is a thin plastic carrier bag over the hole, which it should pull in slightly). I don't remember the idle speed changing dramatically when removing the cap with it running, but I do have a different engine to you. I'm sure one of our other M54 forum member could do this test on their car and report back with their findings??
 
Update: changed the ccv and the return hose to the dip stick was clogged with gunk, had to blow it out of the actual dipstick holder. All replaced and put back on and it still idles the same. Pending code is p0012 after a short drive.
 
If the pipes were so clogged your CCV is done the rubber baffle inside ruptured. Im dealing with mine just now and have decided to delete the CCV and install an oil catch can, will update soon how things go
 
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