Another Idle Problem... help! - United Bimmer Community

**morroman** · 05-16-2007, 02:10 AM

My 92 325i with the M50 engine has a terrible idle problem.

ATM its happens half the time when at intersections etc and it will drop its revs from 1k to around 700. When it drops its revs it will surge constantly up and down from 700 to 800 and eventually surge further up and down until it hits 1k again. After it hits 1k again its sits at 700 nicely and no more surging.

Whats could be the problem???

BTW i have cleaned the ICV and replaced the vacuum hose for the intake manifold (which was totally stuffed).

**c1apton** · 05-16-2007, 03:02 AM

It sounds like you still have a vac leak - check the bellows tube and ALL of your vac lines. You might also replace your fuel filter & run a good fuel system cleaner through it (since you found a "totally plugged vac hose)

**Numark318i** · 05-16-2007, 11:02 AM

^^ what he said.

**bmdude** · 05-19-2007, 01:36 AM

agree with the above posts.. you've probably dealing with some vacuum leaks.. have it checked right away.

**morroman** · 05-19-2007, 01:48 AM

after a day of driving it seems like the vacuum hose that i replaced helped heaps, its only surging within a 50rpm range now. What other vac hoses is there to check???
Also whats a bellow tube and where is it?

**Dudesky** · 05-19-2007, 04:31 AM

The "bellows tube" is the big rubber 90 degree tube that goes from your MAF sensor to the throttle housing. That's a prime suspect for air leaks; cracks develop in the folds that may or may not be too visible just by looking at it. Take it off and inspect it well, inside and out.

**morroman** · 05-20-2007, 01:22 AM

Bellow tube removed, cleaned, inspected and reinstalled. No leaks. Any other hoses that are prone to air leaks?

**Dudesky** · 05-20-2007, 06:08 AM

There are 2 hoses that attach to the sensor on the back of the airbox. Also check your PCV hoses connected at the front of the cylinder head. That PCV breather hose connector also has an o-ring that may need replacement. The throttle body has a thin gasket where it attaches to the intake manifold, and the manifold has gaskets where the intake runners meet the cylinder head. Also check to make sure your oil cap has a good seal. Any of these places, and more I can't think of at the moment, can introduce excess air into the engine.

**morroman** · 05-20-2007, 07:37 PM

Thanks Dudesky, i'll check these and see how i go. Didn't realise how many hoses there are to check.

**morroman** · 07-02-2007, 09:32 PM

Problem solved, O2 Sensor died on Rich. So after a new O2 sensor and quick reset of the DME, baby runs fine, no rought idle or blogging engine, and also no hesitation at take off.

witeshark · 08-18-2007, 11:00 PM

Great news!