Engine starting but not idling...

[TimK]

My 1990 318i starts and then dies almost immediately, unless the throttle is applied and then it will run as normally, but as soon as the throttle is closed it will stall. I have replaced the ICV breather pipe and cleaned the ICV. The main air inlet pipe doesn't appear to have any leaks and I have cleaned the throttle body. The TPS works fine, with good continuity. Any ideas are very welcome as I'm trying to get this sorted myself and not resort to the mechanic...

[e30mtec]

id replace the icv as first port of call pal

[weed1]

You have an air leak between the metering unit and the ports on the cylinder head.
A large one by the sound of your description.

m

[TimK]

I have cleaned the ICV and had it ultrasonically cleaned too. It runs better but the revs drop slightly as though it's about to fall every 6 seconds or so at idle? Also before I cleaned the ICV, I unplugged it, then started and it idled OK, and when I plugged it back the engine surged and stalled. Any ideas? should I replace the ICV?

[e30mtec]

air leak? symptoms sound right pal

[m_jermyn]

Air leak from me too.. Check your big rubber hose from the AFM to the throttle body for cracks... If you dont find it there check all other rubber hoses.

[e30mtec]

start it up ,take oil filler cap off and let me know what happens.if it stays same =air leak if it runs roughor idle drops a bit = no leak..or very small one

[TimK]

Ok will try the oil cap, the thing is it will only idle when warm, has to be left running for about five mins then it will idle lumpily...
I'm pretty sure the big air hose doesn't have any leaks, I have checked it thoroughly. any specific pipes to check? AS I say, I've already replaced the one to the ICV and a small fuel pipe...
Thanks for your help.

[e30mtec]

check ALL the vacuum hoses..pretty much all the hoses around the inlet manifold.i used to have this and never got it sorted.rough idle is probably the biggest thing on an e30....also if you can get your hands on carb cleaner give a squirt into the throttle body or air hose by afm...also just remembered ..on the large air intake hose .near the throttlebody there is a small pipe connected underneath on a 90 degree plastic joint that actuallly goes to the icv..check that is properly connected as i was a muppet and left mine offf then whinged it wouldnt run right ha ha

[TimK]

I have cleaned the throttle body with carb cleaner, and replaced the hose that goes to the ICV, and made sure it fits tight so it shouldn't be that... that's why I'm so confused as to what it is as I've check everything for air leaks, and cleaned everything out

[rmurphy520]

Feel around the inlet manifold gaskets as well as rubber hoses, you could have unmetered air getting in here due to a bad gasket which can cause idling flucuations.

[TimK]

Inlet manifold gaskets are all good too, I have checked them thoroughly. Thanks for suggestions anyway...

[rmurphy520]

But have you actually replaced them? A leaking gasket can be hard to spot.