Idle question after rebuilding cylinderhead
The car is a 1993 190e 2.6L engine
I rebuilt the head with new guides and seals. The car started fine and idled great like before I did the head job. after about 150 miles it started to idle high after start up. To be more specific, I start the car and idle goes to about 900. Let it idle for 5 minutes and it doesn't drop. If I push the gas slightly to about 1200 rpm, it goes to it and stays there. A little more gas to 1500 rpm and goes there and stay at 1500. I noticed that when I unplug the idle valve, the idle goes back normal and stays there when I reconnect the connector to the valve. If I turn the car off and restart it, it goes high as mentioned and drops when I put the valve connector. With the valve connector off and car idling good, turning the A/C on drops the idle to about 400 and car idles failrly Ok. Turning the A/C off brings the idle to about 700 rpm (normal). My OVP is 3 months old. There are no vacuum leaks. I checked the on/off ratio at pin 3 and it fluctuate around 50 so I assumed the oxygen sensor is ok. I haven't checke the EHA current and will do that in the next 2 days. I checked the switch by the throttle linkage and it read 0 ohms at rest position (car not running) and infinety at WOT and even when I move it slightly so I assmed it is ok too. I will clean the valve tomorow with electrical part cleaner and see what happens. Any other things to look at?
PS. The issue happened after I degreesed and washed the engine if that may trigger ideas
1993 190E 2.6
Advanced Diesel Systems Test and Research Engineer