CL55 AMG - Intermittent Reving

[richardN2O]

OK guys thinking caps on. The intermittent fault came back this afternoon. Turn key, engine rev's to 2000 and stays there, blip the throttle it revs to 3000 sometimes 4000 and stays there. Re-start, revs to 2000 again. On approx. the 10th re-start it went back to normal - phew and I was able to get home. The last time this happened nothing showed up on the STAR and just re-starting it restored it to normal.

I'll continue using it until the intermittent becomes more regular or constant, then hopefully we'll find the cause.

 

[NW_Merc]

Idle control valve?

Incidentally has the fuel filter (or filters) been changed?

 

[richardN2O]

Idle control valve?
Incidentally has the fuel filter (or filters) been changed?

Not to my knowledge, major service next spring.
It runs superbly 99.9% of the time and NEVER misses a beat, apart from this very intermittent starting issue.

 

[WG M-B]

Surely it can only be receiving an incorrect signal from the tps, or a fault with the throttle actuator?
Never come across this

 

[andy@pcd-ltd]

One thing that springs to mind is there is a T-piece under throttle body and this might be starting to crack and taking in unmetered air

 

[richardN2O]

Already replaced the entire throttle pedal as the accelerator sensor failed a couple of weeks back

 

[richardN2O]

One thing that springs to mind is there is a T-piece under throttle body and this might be starting to crack and taking in unmetered air

ty, but surely it would run bad all the time with something like that. It runs too well lol

 

[andy@pcd-ltd]

It may only be a very small crack

The other thing which i think i mentioned last time you had problems is these engines also suffer with throttle body issues as well

 

[WG M-B]

I think with the heat the 55k engines generate in the engine bay, if there was unmetered air via a crack in a plastic pipe it would expand/ break pretty quickly.
I may be wrong though and it's a good shout!
Also worth noting that the ecu should pick up this via adaptation values.