85 cold start issue?? Any Ideas??

reddog · 02-15-2006, 04:26 PM

New car...new problem. I just bought my 3rd 928 (1979 5 spd., 1988 S4 auto) and now a 1985 928s. The car has 130K on it and is responding well to love and attention (how can a person stand to drive with broken climate control knobs??). At any rate, the car runs out well once up to temp, but is very sluggish and idles a little slow from start to warm up (unknown actual temp). It starts fairly well when cold, and will idle at approx. 7-800 rpm. Once it achieves a particular temp (unknown actual value) it picks up another 150-200 rpm, smooths out and runs like a scalded cat. I checked the temp sensor II and got values within reason. I have also cleaned the warm up regulator to no avail. The car has a new fuel filter, good fuel pressure, new air filter...I'm at a loss, any ideas? Any and all help is appreciated. Thanks.

jstobo · 02-15-2006, 06:21 PM

looks like you are checking the right things. from the manual here are items to check: ground & plug connections;temp sensor ll;fuel injectors/injection timing;idle stabilizer;leaks in intake;fuel pressure. Do you have the values to check the sensors? For Templl sensor here are some specs. 32 deg-4.4-6.8kohms;59-86deg-1.4-3.6 kohms; resistence at idle stabilizer should be10-45ohms. hope this helps.

reddog · 02-15-2006, 06:45 PM

Thanks for the input. I have only checked the tempII when cold, since this is when the "issue" shows itself. Vaules you posted are consistent with my findings. I've removed, cleaned and applied dielectric compound to most suspect connections. Does the warm up regulator get its signal from the tempII?

jstobo · 02-16-2006, 12:48 PM

Ther is no warm up regulator on an 85. The 85 has LH-Jetronic. The computer adjust all mixtures based on the Temp ll. Another computer adjusts the timing. No cold start valve either. It could be clogged injectors or a vacumm leak. Run some Techron through and see if it improves.

reddog · 02-16-2006, 01:05 PM

Thanks again for the input. My mistake as far as terminology goes. The other component I checked/cleaned that I called a warm up regulator was the idle stabilizer valve (or that's what it would be called it it were and Audi). I was under the impression that this had something to do with the idle speed during warm up. Thanks for the clarification. I'll try the injector cleaner routine and perhaps some "spirited" driving, I think it had been dogged around town quite a bit. Thanks again.