M42 problems, plz help.

[BECKSTER]

AHey R3V I'm posting this for a friend, who I really want to help get their m42 running right.

Here is the deal, after starting her car it will start idling very high at 1200rpm and then after driving if she comes to a stop the car will drop rpms very low and sometimes die, she says it dies quiet frequently.

She replaced the alternator last summer with an aftermarket one, changed all the belts and keeps the car very maintained so I'm leaving towards calling the alternator the culprit since it's not oem.

Has anymore expierienced this problem? Would switching back to an oem alternator fix the issue?



Thanks.

[mike.bmw]

Hey R3V I'm posting this for a friend, who I really want to help fix her car.

Here is the deal, upon starting her car it will start idling very high at 1200rpm and then after driving if she comes to a stop the car will drop rpms very low and sometimes die, she says it dies quiet frequently.

She replaced the alternator last summer with an aftermarket one, changed all the belts and keeps the car very maintained so I'm leaving towards calling the alternator the culprit since it's not oem.

Has anymore expierienced this problem? Would switching back to an oem alternator fix the issue?



Thanks.

Sounds like a vacuum leak or the idle control valve needs to be cleaned (or both!).

[fresh_TD]

Did she recently replace the intake manifold rubber boot?

[unixnerd]

The vacuum hoses under the intake boot are old now and may be in a very poor state, one of mine cracked earlier this year. Symptoms are what you've described.

Have a look at the smaller tubes that plug into the main rubber intake boot. If those are OK pull the top half of the intake manifold (not that hard) and check the rest.

[varg]

M42s are cluttered with hoses under the intake which, when old and cracked, cause issues like this. I'd also clean the ICV.

[uturn]

To try and pinpoint the leaks, with the car running, spray some starting fluid around the hoses and see if the idle takes off. Or just do a smoke test.