Temps have cooled to lows in the 40's in the morning. My kid complained that the car tended to lunge as she stopped while driving to school.

(Aside: car is a 1995 E300D with just under 50K miles bought last Spring. Oil + filter and tranny fluid changes + screen doohickie changed. Heater valve replacement coming up. Kid started driving and was supposed to drive the Talon Tsi to learn how to drive a manual. Instead, she finessed me out of the E300D leaving me with "Mary Poppins," aka Avalon. Wife drives the Tsi).

I drove it this morning for the first time since that complaint was lodged earlier this week. Sure enough, the car feels like it is lunging as you bring it to a stop. However, after it gets warmed-up to normal engine temp it quits lunging. On closer inspection it looks like it is staying (or trying to stay) at about 1100 rpm. After it warms up it drops considerably to 700 or so (IIRC, I can check these rpm numbers and report exactly if it's necessary).

So I'm thinking there most be a feedback system that is failing. I would think that the high engine idle when air temp is cold is to warm the engine quickly. Once warm it drops to normal engine speed.

Under normal circumstances there must be some sort of electrical or hydraulic connection from the brakes to the engine idle control so that when the brakes are touched the idle drops to prevent excessive break wear and also as a safety feature.

Am I wrong?

What do I do about this?

Thanks for your help.

B

PS Yes, I did search first.

ttt

One thing to look for is wiring loom degradation towards the rear of the cylinder head.

The idle speed control system is really simple, there's a speed sensor on the flywheel, and control unit, and a solenoid on the injector pump. Of these components, none is paticularly susceptible, and so, the wiring and connectors are where I would bein looking at this system.

However, I wouldn't do that before I had checked that the accelerator linkage is correctly adjusted and lubricated; ATF being the recommended lubricant for the linkange.

Thanks, N-C.

I lubed the linkage and will test it this morning.

What can you tell me about idle rpm on a cold engine? I'm interested in solving the problem I have but I am also interested in how the control system works.

B

Okay, I lubricated the moving parts on the throttle linkage above the engine and along the right-hand side. I drove the car a short distance and the rpm's again went too high and stayed too high.

I opened the hood and with the engine still not fully warmed, opened the throttle with the expected rpm increase. However, the throttle did not return to the standard position -- it remained a bit open until I moved it closed. I assume there is a spring tensioner somewhere that is supposed to force the throttle to the idle position. Is it adjustable (I mean, to increase tension to close the throttle to idle position)?

B

I had the same high idle problem with my car until I changed the wiring harness. Does your car have the original harness?

__________________
95 E300 Diesel 200K

With colder weather having arrived I'd look to linkage first. Cold grease or linkage end caps slightly misaligned and binding.

Check operation of both springs and see if additional tension will pull the linkage back to the lower idle position.

http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=124131&M=606%2E910&GA=722%2E435&GM=717%2E433&CT=M&cat=19T&SID=07&SGR=125&SGN=05

Beyond that check the wiring harness as others have said. The 95 was prob the worst year as it had more electronic controls/features.

__________________
Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

>>However, the throttle did not return to the standard position

There's the problem! At least it's not going to be expensive to fix.

If the linkage is greased rather than oiled, it may be worth cleaning and re-lubing with ATF. I can imagine the slider on the left hand end of the cross bar will easily stick and prevent the trottle returning fully.

Speaking from personal experience with this car, and having had an identical problem, the first thing I would check would be the engine mounts, If one is defective, then the engine would lean to one side, pulling the accelerator linkage cable with it. Resulting in (intermittent) high idle speed.

You can also try LOOSENING the linkage cable adjustment, to see if that improves things.

Something else you can try next time the engine goes into high idle mode, (although not conclusive) is to physically pull back the accelerator pedal. If idle speed goes down, than most likely it is either a collapsed engine mount (Passenger side) or a linkage cable that's too tight.

Phil

__________________
'95 E300 Diesel, 264,000 Miles. [Sold it]

Yes.

Surely it can't be as insanely involved (and expensive) as with the gasser wiring harness? Say it ain't so!

I pulled the pedal back with my toe (I had a 1964 F100 that would do that, too. I learned how to use the clutch, column shift, and toe the accelerator. It's amazing what you can learn to do when you're too lazy to make the repair!).

I still think there's a temperature component to this. The day has warmed nicely, the engine cooled to ambient, but the throttle isn't over-rev-ing as it did when it was cooler.

I'll try cleaning the whole sheebang with ATF in hopes of removing hardened or thickened lubricants and grime.

TMAllison, thanks for the link. I'll go check it.

To all: Thanks for taking the time to look at this. newbies need hand-holding.

B

This may be helpful;

http://www.w124performance.com/service/w124CD1/Program/Engine/605_606/30-1010.pdf

Wow, nice site!

I apologize for not providing the follow-up/cure.

After cleaning and lubing this and that, the problem persisted. I gave up, being a far better botanist than a mechanic. So I took it o my indy, who also had trouble diagnosing it, which is unusual for him but gratifying to me. He cleaned the manifold intake flaps and checked this n that. Finally he did what I did to make it have a problem. He kept it overnight and tried to start it and drive it, first thing. Got exactly the same problem. He tracked the problem down to an oil pressure sending unit, which he replaced.

Total cost (parts = $97, labor = $150). I figure he could rightfully have tacked another $50 for aggravation.

No problems since.

Bot

sounds like when i get my car home monday i'm going to have the exact same thing done

just got my insurance bill for this thing too... $1,600 for the year!!!!!
i wanna know how these people rate these darn things.

__________________
Matthew McIvor

2016 E350 4Matic Black/Black
2007 GL450 4Matic with Off-Road Pkg Silver/Black
1995 E300 Diesel White/Gray
1994 S600 Euro Black/ Black Velour
1986 560SL Blue/Blue/Gray
1986 190E Blue/Blue 93k