Hi everyone. My son has a 1985 E30 with the M10 engine and manual transmission. He began experiencing idle speed problems with the car last winter, which had been traced by a local shop to either the idle control unit in the glovebox or the idle stabilization relay on the left shock tower under the hood. When the car was started, it would immediately rev up to about 1800 rpm and stay there until it warmed up. Once warm it would violently surge in idle speed and was pretty much undriveable. We couldn't find an idle stabilization relay anywhere locally either new or used, but tracked down a remanufactured idle control unit and tried it. The idle didn't change at all, and the only way that we were able make it driveable was the penny trick, where you put a penny with a hole in it in the idle control valve hose. This worked well until recently when it developed idle problems in the warmer weather. It will start right away, but then idles very low until it warms up or even stalls. I followed some tests in the Bentley manual and found that there was 12 volts at the idle control unit in the glovebox that was supposed to drop out after 2 seconds of the ignition being in the "on" position, but this power never dropped out. According to the manual, this would indicate a problem with the ignition control unit, but I put a new one in today and there was no difference. I also noticed, probably unrelated, that the cruise control servo under the hood continuously hums with the key on, and only stops when you hold the cruise control lever in the "off" position. I have previously changed the distributor cap, rotor, spark plugs and oxygen sensor as part of a tune up along with the fuel filter and air filter. The low pressure fuel pump in the tank was also replaced because it had failed. I don't know where to go next, and we have very few shops or mechanics around us that know much if anything about these cars. Does anyone have any suggestions or advice? Finding used cars of this vintage here is also next to impossible, as I was considering a swap from Jetronic to Motronic to hopefully solve things. Does anyone know if it's possible to upgrade this car from Jetronic to a newer engine management system, say from a mid 90's BMW?
Thanks for any help.
