1994 318i idle issue

aray · 01-30-2009, 09:25 PM

the problem - The car starts however it wont stay running. If i stay on the gas (keeping it around 1000 rpm) it will run, however once I get off of the gas it will drop down to 600rpm and seem to be running good but it will then just die.
I have pulled the ICV out and cleaned it with carb cleaner and wd40. The flapper seems to be doing what it should (I don't have or have never had one to compare). I have also checked or changed the vacuum hoses.

Allen

Manolito · 01-31-2009, 08:20 AM

Did you clean the throttle body passages and around the butterfly when you cleaned the IAC?

Have you checked the connections and resistances at the throttle position sensor? I vaguely recall typing up the instructions and resistance readings for the TPS, either here or over at DTM forums. Not sure if you could still find it.

aray · 01-31-2009, 09:42 AM

Can you elaborate on what you mean by the passages? (Did you clean the throttle body passages and around the butterfly when you cleaned the IAC?)

I will look for your instructions and resistance readings for the TPS

Manolito · 01-31-2009, 12:41 PM

When I clean throttle butterflies, there is usually gunk around the edges of the plate, and there are usually small holes in the air passage that go to who-knows-where, and larger holes that go to and from the idle control valve. I try to get all the gunk out of everywhere that has gunk.

The other thing to check while you are there is to be sure that the tube between the mass airflow sensor and the throttle valve has no cracks in it.

Manolito · 01-31-2009, 12:53 PM

On your car, if you unplug the throttle position sensor, there should be three prongs. Bottom prong is #1 and top prong is #3

Plug off, key on, the plug from the wiring harness should have +5V that it feeds to prong #1.

Plug off, resistance between prongs #1 and #3 on the sensor should be about 4k ohms.

Plug off, resistance between prongs #1 and #2 on the sensor should vary from 1k to 4k ohms as you open and close the throttle. Resistance variation should be smooth with no dead spots as you move the throttle.

Another possibility is the mass airflow sensor. How does the car run at higher RPMs and under load?

aray · 02-03-2009, 10:04 AM

Thanks for the information. I tested the throttle position sensor and it tested good. I'm going to remove the throttle body and make sure its all clean. Thanks again, I will update when done.