Trouble starting & rough idle

[lazlo]

The other night I was unable to start my '91 240, it would crank but not turn over. The next day it did start, but with a rough idle, and the RPMs surged and then dropped until i reved the engine a little bit to keep it running.

I had experenced this same rough idle problem recently before, but never had a problem turning the engine over. Also, occasionally on the freeway the check engine light goes on-- espcially when the RPMs are steady at about 3500 or more. The lgiht goes off when I get off the freeway and the RPMs drop.

Are these two problems related, and does anybody have an idea of whats going on? I tried using a fuel injector cleaner/additive for the rough idle, but it didn't help i guess.

Thanks for your help.

[navysnail]

wiggle the harness connector for the maf around, see if that helps, also cleaning the maf with brake cleaner helps too

[Axel Grungy]

clean your coolant temp sensor connection too

[lazlo]

Sorry to ask a dumb question, but what is the maf?

[benemorius]

Mass Air Flow sensor. It measures the volume of intake air. That's what the harness connector is coming out of the intake pipe right by the airbox.

[lazlo]

thanks alot for the info, i'll try it

[johna_99_99]

let me know if cleaning the MAAFS did anything....thanks

[lazlo]

um... ok -- found the MAF, I could see the filament thing in there and the whole thing looks clean as a whistle. I tried wiggling the harness connector around too. The car starts and it ildes real rough for about a few seconds then it settles in at about 1100 RPM in park.

As far as the MAF goes-- i guess im not sure what to clean. Spray the brake cleaner inside the cylinder?

[johna_99_99]

ya just spray the cylinder thing from about 6 inches away(both sides)...never touch it with anything. i heard also to wait a long time before you start your car again after u spray/clean it.

hope that helps

[lazlo]

Ok - I sprayed some brake cleaner in the maf. The car starts, but I am still having trouble with it idling roughly when it first starts up. Smoke is coming from the exhaust as well. The smoke goes away when the RPMs settle in. I'm not noticing a difference after cleaning the maf.

[fatboy]

that kinda sounds like an egr problem. what happens is the egr gasses start to carbon up the passages and when you start, it has to soak the carbon before it will start which might explain your hard starting condition. just get to where the egr goes into the intake amnifold and get something (clotheshanger or something like that) to hit the carbon off

[benemorius]

lazlo:

Can you describe the smell/color of the smoke?

[lazlo]

The smoke did not have a strong odor, and the color was kind of greyish-- not too dark black. The smoke seems to stop once the idle smoothes out.

[sil80S13]

your aiv valve is connected to ur exhaust manifold and intake air box.. the hose that goes into the air box.. remove it. or if u want open up the aiv and clean the inside with carb cleaner... also there are 3 hoses under the intake manifold..those are vacuum hoses..check that too.. alot of times those come off. the aiv works with the egr.. it dumps hot air into your engine to help warm up the cat. hope this helps.. this worked for my car.

[lazlo]

I found the egr and tested the valve which seems to be working fine. Do I have to remove the egr in order to clean it? or do i just use the coathanger to clear the area below the diaphragm valve?

By the way - in the middle of all this -- my window cable snapped. Does anyone have any suggestions for that? At the very least- i just want the window to stay in the up position, before it rains.

[lazlo]

Ok, fixed it. In case anyone was interested, the coolant temp sensor and the EGR sensor were both shot.