C220 (W202) RPM Surges

[simonpr888]

Can anyone please give me some advice; when i usually start my car with a warm engine, the RPM usually drops almost making the engine die then it suddenly surges, then normalizes at about 7000rpm. This never happens during a cold start. Please help.

 

[Aussie Nick]

7000 rpm for idle is way too high. Did you mean 700 rpm?

 

[simonpr888]

Sorry, that's right, 700 rpm. Anybody pls who can give some suggestions?

 

[mattkh]

Can anyone please give me some advice; when i usually start my car with a warm engine, the RPM usually drops almost making the engine die then it suddenly surges, then normalizes at about 7000rpm. This never happens during a cold start. Please help.

Hi
Is it w202022 ?
What is the mileage ?
How long does it take to normalise at 700rpm ?
On the cold start, what are the rpm for the first minute ?

 

[simonpr888]

Hi
Is it w202022 ?
What is the mileage ?
How long does it take to normalise at 700rpm ?
On the cold start, what are the rpm for the first minute ?

Yes it's a 202022. Mileage is about 60,000 kms. When I start the ignition, RPM drops to about 3 (x 100 so 300rpm), then surges, like the ECU is trying to correct the low rpm thus results to a surge in rpm to about 25 (x100 so around 2500rpm). After about two seconds, it goes down (engine shakes a bit in the process) and normalizes at 700rpm. On cold start, I think it's normal, for 20 seconds it goes around 1300rpm then goes slowly down to 9 - 8 then after a minute stabilizes at around 700rpm.Your thoughts please...

 

[mattkh]

Hi
Is it a diesel ?
What is the outside temperature when you do the hot restart ?

 

[simonpr888]

Hi
Is it a diesel ?
What is the outside temperature when you do the hot restart ?

No, petrol engine. Outside temp is about 26 ~ 32 celsius. I live in the tropics. Any ideas?

 

[mattkh]

Hi
Next time you do a hot restart do as follows:
1. Turn ignition ON but dont turn the starter. Then turn ignition OFF.
2. Wait 10 seconds.
3. Turn ignition ON and turn the starter.

Tell me how the rpm changed.

 

[simonpr888]

Hi
Next time you do a hot restart do as follows:
1. Turn ignition ON but dont turn the starter. Then turn ignition OFF.
2. Wait 10 seconds.
3. Turn ignition ON and turn the starter.

Tell me how the rpm changed.

Hi, I did as you instructed, but nothing changed. Still drops then surges on a hot restart. Any other ideas? Thanks