M42 idle problems

[mikeedler]

I know most of the crap under the intake is a bit old, but none of it is outright cracked and sucking in a noticable amount of air.

sometimes the piece of crap idles o.k.(less often), sometimes it idles like its on 3 cylinders, and sometimes it idles at 2000-2500rpms.
the other day after running it at 190-220 kmh for about 15 min. straight on the autobahn, it would idle good in town, but it had ZERO power under 3000rpm-- this was for about 5 min.

so question is--- is there any easy fix or something you guyyzz know about that.

please don't say replace all the crappy ass hoses under the intake. the car was free and is my winter crap house-- I can deal with the way it is, but it would be nice to have it correct too.

thanks.

[carguy101]

I would clean the ICV on the back side of the intake. Another good resource for information is M42club.com. Good luck!

[KenC]

I'd be less worried about the idle and more worried about the power loss. That's quite an array of symptoms.

The idle might be fixed by cleaning out the ICV, but M42s are VERY sensitive to vacuum leaks at idle.

I'd try swapping in a known good AFM and/or ECU and start from there.

[Balleristic31]

If u don't wanna replace all the hoses, pinpoint the problem area by spraying around with brake cleaner. Find the problem and just replace/fix that hose

[mikeedler]

If u don't wanna replace all the hoses, pinpoint the problem area by spraying around with brake cleaner. Find the problem and just replace/fix that hose

problem is I know when I start on one hose, they are ALL going to fall apart and have to be done. before the winter I replaced EVERYTHING including the heater core that had to do with the cooling system. way over budgeted my free winter beater!

I will try the ICV cleaning, but an air leak seems to be kinda odd, seeing as it idles high/low/good/crappy all within 1 15 min. drive.
is the AFM interchangable form the M20?

[KenC]

I'm pretty sure the AFM is an M42 part. The ICV seems unlikely to be causing such a wild idle. The power loss is what would concern me. The fact that it's intermittent makes me think AFM or ECU. Maybe FPR??

[mikeedler]

yeah, the car is kinda a problem child. the oil I have now changed twice due to (thin oil)

after about 150 km after a fresh iol change, I checked the oil and it seemed to be VERY watery- but perfect color. so I changed it again thinking, who knows what was in the crankcase (i got the car out of a junk yard).

well, another 150km and it seems to just run off the dipstick like water running off-- but the color looks like BRAND SPANKING new oil. coolant is ok, and it doesnt overheat.

I think I am just going to not open the hood anymore and hope I make it through the winter.

[KenC]

Weird. WTF is thinning it out? Smell like gas at all?

Try doing a quick compression check.

[mikeedler]

no, doesnt smell like gas either ??????? like I said, i think i am just going to keep the hood closed until it won't start anymore.

[KenC]

Throw some 15w40 Dino in there with a bottle of Lucas oil stabilizer. If it was free, I'd say just run it until it dies.

[goinstrong]

While it sounds like a vacuum leak or ICV, there is the possibility of a bad 02 sensor as well....
I replaced mine recently, and the rough idle/variable idle went away. However, all hoses had been replaced under the intake, so vacuum leaks were eliminated.
Good luck!

Tim

[mikeedler]

changed the AFM today, still runs the same. tried to turn the idle down with the set screw, but it is already all the way down. I think it i a vacuum leak!! AHHHHHH!

after some research, I found out the AFM and the ECU are the same as the 318i M40 euro cars.-- tons of those around over here.

[mikeedler]

so, just to put an end to this thread, it was def. the idle control valve. it was stuck in one pos. and due to all the vacuum leaks in the brittle hoses, it could still hold and idle that way.