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idles switching back and fourth

1K views 15 replies 1 participant last post by  Guest (MBNZ) 
#1 ·
I have a 1987 190e 2.6 that when the engine warms up the rpm rev up and down between 600 to 2000 rpm constantly. I've clean the air intake chamber and replaced the cap and rotor with no help. Any advice would be appreciated.
 
#4 ·
Hi<br> I just had the same experience. It would sit at 600 sometimes aqt idle but othertimes would rev to 2000-2500 and actually peel out in reverse in parking lots (very embarrassing).<br> <br> My mechanic (for $45) cleaned my idle stabilizer and sorted out the problem...haven't had issues since. He said if it didn't fix the problem he'd have to change it or the idle relay switch<br> <br> good luck <br> <br> ssb<br> <br> 190 2.6 1991 with 115K miles
 
#5 ·
The reason I ask is, I experienced the same thing<br> after the car warms up.Unless you or somebody<br> tried to alter the air fuel mixture,and you<br> are running rich,it will do the same thing.<br> Another possibility is your ignition coil.<br> If these parts are still orig.(02 snsor.ign.coil) <br> have it check by a competent MB tech.They should have the right equipment to test it.The only<br> way to trouble shoot it.Good luck.<br> Manny A<br> <br> <br>
 
#7 ·
The car seems running fine once is in gear-in drive, idles ok with foot on the break, does run erratic in reverse as ssb describe above, i have not had a chance to check out the idle stabilizer. I don't have the shop manual, would you know where that's located?
 
#10 ·
Idle stabilizer location

I've got no clue, my trusty mechanic diagnosed the problem and cleaned it for me. One of these more experienced guys could probably help you out. Your problem sounds identical to mine. You may want to try one of those fuel system cleaners, I don't know if fuel ever sees the idle stabilizer, if it does you have nothing to lose, however as my mechanic cautioned me it me be the electrical relay portion thats faulty. Does it ever correct itself and behave normal? Mine would about 30% of the time.<br> <br> good luck<br> ssb
 
#11 ·
Idle position switch testing

The Idle position swtich is located on the throttle linkage on the side of the intake. The switch is a little rectangular thing, gray i believe, but i could be wrong. When the car is at idle, part of the throttle linkage should hit this switch. If this isn't happeneing, adjust the throttle linkage. If this is happeneing you need to test the sensor at the ECU. When the throttle is closed, at idle, the voltage on terminal 7 of the ECU should be zero to 0.5V. If it is not, and the throttle linkage is adjusted properly, you need to replace the switch. When the throttle linkage is not in the idle position, the voltage at terminal 7 should increase with the battery voltage.
 
#13 ·
I had disconnected the cable/plug on the idle valve while the problem occure and the problem disappeared. Reconnected cable/plug and the idle goes up and down. Ordered the idle valve for replacement. Mean while, can the car be driven with this cable/plug off? Thanks for all the inputs, Manny A, ssb, G. Carstens.
 
#14 ·
If the car idles normally,(525 rpm)I guess you <br> can.If its much higher than that' I would say no.<br> Very dangerous.It might shift to 1st gear and<br> accellerate tremendously.Not to mention the damage it will do to your trans,flex disc and diff. <br> Be Carefull!I'm sure somebody will clarify this.<br> Manny A
 
#15 ·
Peter - what was the answer? I have the same problem.

Peter- did you solve the puzzle? I am experiencing the same problem on my 1988 2.6L 190E (5-Sp). I have been having a very difficult time with warm starts. I thought it might be the check valves, but then the idle started to surge the other day. Just about the same time you posted you concern. Hhmmmmm. Anyway, what have you found out?
 
#16 ·
Re: Peter - what was the answer? I have the same problem.

Trex, the problem seems to be the idle valve. It is located under the air filter housing tray toward the front of the engine and has an electrical connector on it, I disconnect the electrical connector while the idle was fluctuating and the problem stopped. There is a picture of the idle valve at www.thebenzbin.com under part# 000-141-22-25. good luck.
 
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