Cold idle trouble

Rand · 12-10-2003, 01:50 PM

I have an 85 318i
When I first start it, it runs VERY rough and won't idle unless I keep my foot on the gas
After it warms up a bit, it runs much better, still idles a bit rough but hey, it is old

Any ideas what may be causing this?

Jared at Pelican Parts · 12-10-2003, 01:55 PM

Hmm, The first thing i would do is check that all the vacuum hoses are in good shape, especially the boot from the fuel distributor/Air flow sensor to the throttle body and the o2 Sensor.

The second cuprit may be the aux. air regulator. Sometimes, these can get crudded up with oil mist and vapor and get blocked. The aux. air regulator works kinda like a choke, allowing extra air to enter the engine when it is cold, as the engine warms up, a temp sensor sends a signal to the regulator, causing ti to close. The regulator may not be opening at all when the engine is cold.

The last thing you may want to check is the warmup regulator, however im not sure if the later 318i had these or not.

twoisnice · 12-21-2003, 05:45 AM

I have another tip for you ...

Your cold temperature sensor on the thermostat housing is probably shot ... not telling the cold start injector to supply fuel when the car is cold, so it runs too lean until it is warmed up.

Some advice - start the car and feel if the injector is pulsing ( the one with the blue connector on the intake manifold) if it's not, the cold temperature sensor as mentioned above, is shot, if you feel it pulsing then the calibration of the injector is wrong, or the injector is blocked, not spraying fuel anymore, but only dripping fuel, which is not sufficient for cold starts.

KC Ron Carter · KC Ron Carter's Garage

I would be suspect of the IAV, Idle Air Valve.

Do you know SAM?

http://www.mesaperformance.com/faqs/idle.html

Later,