Warmed up idle puzzle.

[nightsurfride]

I am working on a 1982 320i. A few days ago it started to die after it had warmed up anytime it was returned to an idle position. When it was cold, it idled fine. Off idle, it ran perfect, but come to a stop light and let her idle when warmed up and she would slowly drop from 800 RPM to stall in a matter of seconds unless the driver gave it a little throttle. Yesterday, the car simply would not start. It was determined that the main fuel pump died and after replacing it, she runs again. The new pump did not however fix the idle problem that still lingers. This idle problem has never occurred in the vehicle before it started happening a few days ago. Could it have something to do with the uncanny timing of the fuel pumps death? Perhaps a clogged screen on the pump in the fuel tank caused the main pump to overheat and at the same time starved the system of enough fuel pressure, but I would think it would idle fine and have acceleration and loss of power problems rather than idling issues. Should I look at adjusting the idle speed screw and/or idle mixture screw? Could a plugged or misadjusted auxiliary air valve or air flow sensor be at fault? Any suggestions of where I should start looking to give this car a warmed up idle? Thanx

[sp0rky]

I had this same problem and it turned out to be my airflow sensor. One of the wires was broke. My symptoms were idling really low and / or stalling, and having a bit of a hard time getting off idle above 1k rpm. but after that it ran smooth and all, just a little more powerless than usual.

could be the same for you, but im not sure. i guess its worth a look

[KC Ron Carter]

The e21 had a CIS injection system.

I would be suspect of the WUR, Warm Up Regulator.

It controls the fuel pressure and sets the warm fuel pressure also.

Here is a diagram of the issues.



Of course the AFM, Air Fuel Mixture can be set to max RPM with a 3mm allen wrench.

Later,