idle speed
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I think you will find it is normal that your idle speed goes up when you are driving. If it goes way up, and stays up it probably has something to do with your foot on the go faster pedal. Make sure you look out of the windscreen when you do that.
All joking apart. Idle in gear and standing still should be 500rpm. There is a control circuit which involves an air valve which controls the idle speed. Most likely the air valve is getting blocked and is sticking.
It sounds like you have a vacuum leak which allows extra air into the system, but only after it gets warm. Some component somewhere expands with temperature and opens the breach. Let it cool and it shrinks back into place. Is this new or has it always happened?
After getting my 83 380 road worthy I started driving it and it was idling nicely. One day it would start idling high at stop lights intermittently and then continuously. It would idle at around 900 RPM -- in neutral.
It turns out that there 2 thermal sensors the idling control module is receiving information from. The coolant sensor, on the rear of the right bank, and the oil temperature sensor near the oil filter.
I took an ohm reading of the oil temperature sensor and didn't get a reading, so I replaced it with a Bosch unit off of AutohauseAZ. It solved the problem. Its been idling beautiful since. I also replace the coolant sensor as a preventive measure.
Hope that helps.
It turns out that there 2 thermal sensors the idling control module is receiving information from. The coolant sensor, on the rear of the right bank, and the oil temperature sensor near the oil filter.
I took an ohm reading of the oil temperature sensor and didn't get a reading, so I replaced it with a Bosch unit off of AutohauseAZ. It solved the problem. Its been idling beautiful since. I also replace the coolant sensor as a preventive measure.
Hope that helps.
The idle control units are notorious for going bad. The unit is a plug and play black box. Lots of info in the forum on it. Pull the glove box out and it's a 5 min repair. My high idle was in park and when warm at stop lights. I ordered a remanufactured unit from programa. They allow for a return with a restocking fee. I narrowed down possible sources of the problem and threw the right part at the problem. I may also have a slight vacuum leak somewhere as it sometimes gets rough at a stoplight. But I am no longer putting the car in gear at an rpm double what it should be. My safety concern and possible transmission problem in the making are gone though.
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