Date registered: Jun 2005
Vehicle: GL 450 2008, E320 CDI 2005, E320 1994, 190E 2.6 5-speed(sold), 1995 E320(sold)
Location: San Diego, CA
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Strange idle surge problem
I need some help to pin point my car’s strange idle surge problem. I did a search in the forum and found lot of useful info but still not able to solve my problem.
Thanks to GDC and others for all the useful info.
Car: 1995 E320 with 129K
Cold start: starts fine, engine RPM around 1000-1100 and gradually come down to 700 RPM when gets warm (my other car 1994 E320 warm RPM is around 500, I don’t know why this car warm rpm is 700. Is it abnormal?)
Problem starts when the engine is warm, I mean when I start the car with engine temp between 40 to 80 (the instrument panel temp gauge). The car RPM will go from 700 to 1100/1200 then comes down to 400-500 for a second or two, engine shakes for 1-2 seconds and RPM goes back to 700 and no problem after that All these happen with 2-3 seconds. If I stop the engine and restart right away or even after couple of minutes, it starts fine. Rest of day, all day driving, at stop light no issues at all. The problem will recur if I wait for more than 15 to 20 min after stopping the engine.
The stalling is related to warm engine temp after waiting for more than 15 mins. I have replaced coolant/engine temp sensor, no cure. Replaced engine wiring harness, voltage regulator, changed MAF sensor from my other car which is working fine on that car, no cure. Checked the battery voltage at normal rpm and at 2000 rpm, no surge in voltage.
1. The air pump never comes on with cold start. I purchased rebuilt air pump, no luck. Replaced with another rebuilt one, no luck. I can not figure out why the magnetic clutch of air pump will not get engage, connections are ok.
2. Cruise control stopped working. Tomorrow I shall open Throttle Actuator and look for wiring degradation. I have already bought a used TA and cleaned it today. I need to buy the torx bit to open that.
3. The check engine light came on twice during last several months with code 4 and 8. While checking the code I noticed a small noise, something like a telephone dial tone type sound coming from the throttle actuator area, I can not pin point the source. After deleting the code it goes away.
I can not make any logical explanation for these strange behaviors. Any help will be appreciated.
Thank you all.