W124 E220 (M111) idles high...

[jeffreyli86]

Strange, but I've replaced the Throttle Actuator already.
It's not hunting or anything, it's just higher than usual.
Basically, it is 950rpm when the car is hot in P or N gear. Drops to about 850rpm in Drive. Same revs whether or not the AC is on.
When cold, it can reach 1500rpm, which seems normal.
Car runs great, but would like idling to be lower, or shall I say, be back to normal. :Oops:

This video shows the revs when the car has just been started. It's been sitting for several hours so not totally cold but cold enough to trigger the cold idle (i.e. 1500rpm). It does drop down to around 950-1000rpm after a minute or so if you leave it over night.
http://www.youtube.com/watch?v=uGi9wFNEfoM

This second one is with the AC on, car operating at the normal temperature. You can see that it idles at 950rpm in Neutral and 850rpm in Drive (note the sudden, but slight, drop in revs during the video). Sorry about the music. I don't know how to mute the sound. :Oops:
http://www.youtube.com/watch?v=1TlDuAZYicY

Any ideas anyone? :neutral:

 

[roofless]

check the condition of the of the wiring loom.....look for crumbling insulation

 

[jeffreyli86]

Thanks for the reply mate, but it's got a new harness.. Any others?

 

[124coupe]

Is the high idle since the new throttle actuator was fitted? If so, did you reset the ECU after fitting it to learn the new closed throttle value etc?

Otherwise it may be running on a default map because of a dead or out of spec sensor - have you read the fault codes, if any?

 

[124coupe]

Also, are you sure the throttle cable etc was adjusted correctly with the new throttle body?

 

[roofless]

try blocking off the vac pipe from the regeneration valve to the throttle body just to rule it out it could be stuck open

 

[jeffreyli86]

Thanks for the replies!
The high idle has been there before I changed the Throttle Actuator. In fact, I bought and replaced the TA just to try. My previous one was just 20000km old.
Cables and other linkages seem to be correctly adjusted, and it is not pulling on the TA at idle. It's got a new throttle cable too if that matters.
I haven't read any codes because I don't really know how to make that code reader. Is there a better way to read the codes?
What are the symptoms of it running on the default map?

Cheers,
Jeff

 

[jeffreyli86]

Oh... I don't know if this matters, but I got another MAF from the mechanic (he took it off a car that is having its engine rebuilt, but relatively new MAF). I put it on and the car drove REALLY sluggishly.. But after a while it seems to be better, though still not as good as the one that was on my car.
So I put the original one back in my car, and initially the car stalled twice when I was taking off from a set of lights. But then the problem cleared up (think the ECU learnt it?) and the car was back to how it was.
Idling was very very slightly lower with the other MAF. I'd say in the region of 50rpm.. I idled (in drive) at around 800rpm in Drive, but still around 950-1000rpm in Neutral.
Anyone care to shed some light?

Cheers

 

[jeffreyli86]

try blocking off the vac pipe from the regeneration valve to the throttle body just to rule it out View attachment 7877 it could be stuck open

Cheers mate. Where about is that? I actually tried unplugging the vacuum lines at the Intake Manifold and see if it returns to normal but the engine just became unstable once I disconnect the vacuum lines one by one.
Should I unplug them and block them instead to try?

Thx again!!

 

[S80]

When my regeneration valve (on the left-hand inner wing) stuck open, the effect was the reverse - the engine tended to stumble and stall.