Uncontrolled idiling

[Marc Taylor]

My 1995 E200 (W124) has a problem with uncontrolled idiling, on start up it revs to 2000 rpm and then after a minute falls to about 700rpm, the same thing happens when you go from D into N or P. I have taken the car to my local dealer and on their instructions have fitted a new exhaust, nem manifold gasket, new lamba sensor and a new throttle control unit (the unit that houses the throttle flap) but it is still revving at about 2000 rpm for about 1 minute on start up and when in P or N. Can anyone point to what else could it be?

Thanks

Marc Taylor

 

[42847]

fast dle

3 yrs ago my 1984 380sl v8 was same i took a wire off distributor advaace retard or something it has been perfect ever since

 

[Marc Taylor]

Thanks for that but my model is the 16v and has not got a distributor fitted to it.

 

[Bolide]

Late petrol W124s jump to 1500-2000 rpm on startup and hold 1st gear to about 3000 rpm as part of the warm-up routine for the catalyst. It's normal

Nick Froome
www.w124.co.uk

 

[Marc Taylor]

Thanks for that, but I am also having the revs jump to 2000rpm when I go from D into N or P after a run and also when I rev up in P or D it take a long time for the revs to fall down to around 800rpm. Do you think it could be the ECU at fault as it originally failed its MOT with a high CO level due to the uncontrable idiling. I appreciate any help in this matter.

 

[Bolide]

Logically it's the ECU or something that sends signals to the ECU like the MAF. When you bring the box out of Drive the load on the engine decreases and the revs rise. If the ECU is slow to stablise that change either it doesn't know what it's doing or it's getting the wrong signals

I think you'll need a Star machine to find out what's going on


Nick Froome
www.w124.co.uk

 

[kth286]

Marc Taylor

First thing is to get the codes read.

What codes were present ????

The ECU only does what the input sensors tells it. So it's likely an input sensor feedback problem.

That's why it is important to get the codes read, as it will tell you which sensor is out of spec.

Has the car now passed MOT and what was done to pass it ???????

Regards

 

[Marc Taylor]

Thanks, I will see about getting the codes read to see if it a sensor that is gone.

Marc

 

[Marc Taylor]

The problem may have been solved. While waiting for an auto spark to come to check the codes on the car I decided to change the fuel filter. Once it was changed I started the car and it did not rev up like it was and when you now rev the engine the rev counter rises and falls with no problems. So it will be going for its MOT on Monday so hopefully it will pass on the emissions this time.

 

[Marc Taylor]

I have managed to solve the problem with my E200. After spending hundreds of pounds on a new exhaust and other items, all it came down to was a £10 fuel filter. The car passed its MOT last week and I am now back behind the wheel. Thanks for all you help.