£ C43 £ AMG £

Hi all any ideas will be appreciated?

Place car in P or N and rev engine and revs get stuck around 2k,
turn off and start again or put into D and its fine until revs are applied again in P or N. Drives no different.

This has happen after I changed the valve cover gaskets and steam cleaned the engine! Checked hoses/coil packs/leads but not much was disturbed in the first place.

Is the throttle body getting stuck and needs servicing or is it something to do with the recent work?

cahiil55k

I had that happen once when I had the y-tube on my 82mm throttle body repositioned. My tech had to do something on STAR to get it to stop. I think he said he reset adaptations.

vinnyz

happen to me when i changed valve cover gaskets too .. in the back side of engine hose wasnt on .. at the time had no idea what it was till did smoke test and found it . take off airbox and look all in the back side of engine around throttle body area and it will be back to normal

lowprofile

Sounds like a classic vacuum leak. The hose from each valve cover connect to a "t" which connects to the bottom of the throttle body. I would start there and make sure that "t" is connected firmly to the throttle body.

£ C43 £ AMG £

Thanks people for posting your exsperiences so far.

Its frustating when you cure one problem another one is created, I hope my steam clean which I did last week did not cause this ............(I know and please dont remind me that its always a risk, but it was covered in oil from the gaskets leaking)

I am 99% sure when I checked all the vacum hoses agian last night that they were ok and the one to the TB was secure. Maybe I have a split I cant see..........

I will check/remove/replace agian and if I cant see the problem I will block up the TB inlet hole just to test and see if it stops the high idle problem

£ C43 £ AMG £

I am now 100% sure after checking all the vacum hoses again and behind the TB that they are OK, I pulled both sides off one by one and there is a strong vacuum suction in each pipe back to the TB/T-piece...which gives me piece of mind that its not leaning out the fuel mixture.

I am thinking it was doing this before I changed the gaskets as I have rarely revved the engine in Neutral or Park and the problem is the TB.

Tonight on checking and testing it was intermittent with no pattern, sometimes it would stay stuck at 1500-2000 revs would and some times the revs would drop back down and sometimes they were delayed in dropping back down.

Has any one else noticed their TB butterfly opening and closing ever so slightly (I can just see it almost vibrating when I stare at it closely), as I can only assume it should be still on idle?

pun1sh3rz

yeah, just had my valve cover gaskets changed and am having this same idle probelm along with a handful of others.

cahiil55k

You might also want to try a throttle body reset. Skratch77 sent me this before for an unrelated issue:

clear codes (if any)
shut off car
unplug tb plug
turn key to position 2 for 10 seconds
key off position
plug tb back in
key second postion for 20 seconds
off
start car

£ C43 £ AMG £

Please describe the issues you are having, this is too much of a coincidence as there are a few members on here saying the same thing after changing the gaskets.

I cant get any faults to show up and also no CEL.
Honestly, I was very very careful and meticulous when doing the work, I also resealed the breather covers and used new bolts, I tightened the covers in the same way you do a head gasket and checked everything more than twice. The only thing I did not put back in the same order were the coil packs as these were all put in a box together after removing them.


Thank you cahiil55k I will try the reset on the TB also.

This is just a BIG coincidence, were the gaskets leaking so much, that the crank case pressure was lower and now it needs a reset, I find that hard to believe.

£ C43 £ AMG £

Same idle problem, happened more today once engine got hot and not once while it was cold. Two days ago it was the other way around

Also the reason I changed the leaking gaskets was I due to a smell in the cabin,
same smell this morning again after a week of changing the gaskets. Checked and no sign of leaks.

O well the next thread I start will be

"E55 ON FIRE"

what a shame I feel, I am going to burn it and move on.

£ C43 £ AMG £

ok I decided not to burn it.

PLEASE IDEAS ANYONE

as I have worked out that after I rev the car in N or P and the revs get stuck between 1500-2000rpm , when I turn the steering/wheels the revs always go back down to normal 750rpm? but only when I do this?

lowprofile

Still sounds like a vacuum leak. The extra load from the power steering pump is pulling the idle back down when you turn the wheel.
Have you sprayed around the intake and surge tanks yet? Do you have a scan tool?

£ C43 £ AMG £

Thank you for confirming, I just thought that because it was not always happening that it might be an electrical prob and not an air leak.

not sprayed yet, but I will do................. best spray to use?

lowprofile

Carb cleaner is what I have used, but you could use propane too. If you have a scan tool you could check the throttle opening percentage, ~3% is normal when warmed up.

£ C43 £ AMG £

Hello again

went through two tins of carb cleaner today, engine is starting to look very shiny and new.

the only area that was effected when spraying was just under the TB on the right side as you face the car, next to the T piece vacuum there is a black hard plastic type piston that you can physically slide out and springs back in............??

Is this a pressure release valve or is it a cold start component??

lowprofile

On my cell right now. I'll check it out when I'm home.

blackbenzz

Are you also getting the blinking fuel light? It does sound like a vacuum leak.

£ C43 £ AMG £

thanks, but I am not aware that I am getting a blinking fuel light issue or familiar with what it means?

what is the function of the piston plunger under the TB?

blackbenzz

I don't know what the function of that is. It sounds like you have a vacuum leak though

MBTEK

VERY COMMON ON 55K CARS THAT PEOPLE DO THEIR V/C GASKETS ON. REMOVE YOUR AIR CLEANER ASSY,TAKE A FLASHLIGHT AND LOOK AT THE THE SILVER METAL LINE THAT IS YOUR PURGE LINE @ THE LT. REAR OF THE ENGINE. YOU PROBABLY TOOK IT OFF WHEN DOING THE COVERS CAUSE IT'S HELD DOWN BY ONE OF THE BOLTS.LOOK REAL CLOSE WHERE IT GOES INTO THE BACK OF THE CHARGER,IT'S REAL EASY TO MISS THE GROMMET IT SLIDES INTO.HOPE THAT HELPS.

pun1sh3rz

^ you were absolutely correct, it was tough to see back there. I'll let Ahmad shed some more light on this if he wishes. Thanks MBTEK

blackbenzz

+1, thanks MBTEK This is not something you would catch on a visual inspection because its hidden down beneath other things and you cant see it. I thought Audi had retarded designs but looks like MB has at least one too. Didnt have a mirror so we had to use a camera to take a picture of what was going on down there. Sure enough the metal hose was no longer in the grommet. OP should definitely give this a try

£ C43 £ AMG £

AMAZING MBTEK SPOT ON

I removed the TB and got a mirror out, it was very hard to see the hole and the end of the pipe.

Took a while to find it, but once I saw what you described, the problem became crystal clear.

I did not have a clue that the pipe behind the supercharger could just pop out without the bracket attached when I removed the valve covers.

Why does it not throw a CEL, is it not running lean, I know we dont have an air mass meter, but what about the exhaust O2 sensors.

THANK YOU ALL FOR YOUR HELP AND ADVICE it has been very much appreciated credit to all.



(hmhmmm....... shall I fit a catch tank....... given the amount of oil that I saw inside the supercharger inlet)

Austinsec

anyone have a picture of the location of the hose