w126 low idle in all gears - PeachParts Mercedes-Benz Forum

ptrip6 · #1 01-08-2006, 04:30 PM

I have an issue with the idle on my '85 500 SEC. Before I start to play with any of the idle linkage, I wanted to see if anyone might be able to steer me in the right direction. Recently the car went from running fine to occasionally stalling when I would begin to put it into gear about 2 weeks ago. Just the other day the car would not start at all. After recharging the battery and starting the vehicle, I had a very high idle and reviewed some of the old post and tried to figure out the problem. I bought a new dist.cap and rotor thinking that was my initial starting problem. Turns out the battery was no good so I replaced it with a new one. I looked into the Idle control valve and I dont know if this was good or not but it seemed as if the valve was stuck in a partially opened position so I cleaned out some of the black gunk in the valve, because when I unplugged this valve connection there was no increase/decrease in RPM. Now the car starts and runs with a very low idle. Ive never had the car run so quietly. I thought this might be good, but when I went to shift into R,N,or D. there is very little idle change. Going back to check the ICV connection, when I unplug this connection, RPM do not change at all. I thought I would test drive the car and see if cleaning the ICV might have screwed something up so I drove it hard and it seems to run fine. Maybe a little slower with initial take off but no real hesitation at all. My only problem is the low idle (200-250 RPM) The mileage is coming up on 249,000 miles and I had the timing chain replaced, and heads serviced about 18 months ago. I would like to find this problem before going and spending $ on diagnostics tests... Any guidance in the right direction would be greatly appreciated.BTW, I am not good with elect. issues and need more help in that area if possible, if needed. Thanks, Rich

Two560Two · #2 01-08-2006, 07:50 PM

You might need a new idle contol unit. Low idle or high idle are symptoms of the idle control unit being dirty or about to break. Replace the idle control unit first and see what the results are

ptrip6 · #3 01-08-2006, 09:11 PM

is the control unit you are talking about the one in the engine compartment between the firewall and front winshield on drivers side? Or are you talking about the unit that is inside on passangers side kickpanel...?? Is there a way to test this unit myself without screwing it up? Thanks for the feedback..

86560SEL · #4 01-12-2006, 06:43 PM

PTRIP6:

Did you ever figure out what was causing your stalling out? My W126 is also stalling occasionally when I place in gear. The only difference is that my car idles fine when in park (about 750) and in gear (about 500). Its just when I place my car in gear, the idle jumps down so low at that point, that it stalls.

It is very embarrassing and annoying to say the least.

Thanks.

ptrip6 · #5 01-18-2006, 03:42 AM

I ended up replacing the Idle control unit and the idle control valve and now my car runs great. Thanks for the feedback.

zcc · #6 01-18-2006, 11:37 AM

What if it was on a high idle? Let's say at 1 (1000 RPM)?

On my dead 380SE 1984 it was on 1 and no one could fix it after I did every possible thing.

I'm asking just for curiosity : ))..