c32used

Ok on Saturday(8-3-13) I had a friend change the CPS(crank positioning sensor) boy was it a major PITA! I read about it first but couldn't seem to follow the under the car route....ended up using a combo of both under car and above car. Anyway though I tried both routes I found myself having to remove the Drivers side plenum to give the friend mechanic more room to reach area where CPS is..anyways after replacing CPS and putting Plenum, Air boxes back as original and resetting engine alert everything seem fine so naturally I presumed all was ok thus drove car normally.............all seemed fine then the engine alert shows and my dash says check gas cap needs closing I think...anyways got to my destination and checked gas cap and took it off and put it back and cleared code and back to normal but I noticed then my idle on park was around 2k rpm. I went home and about 80% return home and same codes show up and I stopped and checked gas cap again and rest error code..anyways got home eventually and noticed once again while in park my rpm was high again. I today 8-4-13 reset error code and checked visually and all looked good under airboxes. I turned car on for a while no codes so presumed ok. So took a little ride and upon return once again noticed higher rpm then normal this time around 15k. The prior codes where P0451 and P0455. They have yet to alert again but figured I ask. Once again all done was CPS replaced all removed. So confused if this is new or related to CPS replacement. Help please!

Lenin

Maybe you have a vacuum leak. Did you use a new gasket for the plenum? Do a "sneaky ECU reset" and see if the idle goes back to normal.

c32used

No didn't replace but checked prior to reinstall of it....ECU rest? You mean disconnect ECU from power?

saer1one

I also removed my air box a couple weeks ago to clean my air filters causing the check engine light to come on the day after and also causing the car to idle at 2k rpm. The code was also P0451. I searched the forum and found a thread started by chris.bachman where he states he was messing with the air box during his dyno run and pulled the same code days later but root cause was found as to why the engine light came on. I erased the check engine light the first time while the second time it erased itself only minutes after coming on. That was last Tuesday and it has not appeared again but my car still sometimes idles at 2k rpm, I still cant figure out why..

Lenin

ECU reset.
https://mbworld.org/forums/w211-amg/...set-works.html

It is not advisable to reuse the same gaskets.

saer1one

Trying this before work.. Thanks Lenin..

Robert AMG

iTrader: (1)

check the pipe that connect to the tb, also the pipe that connect to the tb plenun that goes to the fuel filter/regulator, one of them is no connected.

mb techman

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c32kompressor

there is a vacume line going into the bottom of the throttle body. its black and runs to both sides on the engine. (both banks) into the valve cover. under the throttle body is a T splitter, there will be a hose that slips into the bottom of the throttle body, If that's loose or not connected it will indeed idle that high. pull the intake off again and check for that hose..... since you took the intake plenum off, you might have accidently pulled the hose out.

JamesC32

I put a new CPS on my car when I replaced my gas peddle and it was still throwing the codes, I couldn't figure out what was wrong and finally after months put my OLD CPS back on and then everything was fine, it was a real pain that the brand new one was bad, it was purchased at ORIELY'S,, just a thought.

c32used

I am going to finally work on it today...it was very frustrating to work on CPS that last minute choice was to remove the plenum. If codes continue I will buy gaskets but I have a feeling it's a hose leak. Thanks guys for all comments pretty sure(hoping) it gets resolved :-)

saer1one

Keep us posted.. I haven't removed the air boxes to check the throtle body vacuum line so my car continous to idle at 2k rpm..

c32used

Well all seems good now as I thought had to be a hose that got disconnected...so removed airbox and "Y" splitter all looked good and was about to remove right plenum(driver's side) then my friend saw a line disconnected in between left plenum(passenger side) and SC(look at picture). It had to have been pulled out and unnoticed. Pushed it back in and put all together and cleared code and took a good drive and no RPM spike nor error codes....all seem fine now. Case closed unless issue arise.

saer1one

Nice..! Glad it was only a vacuum hose..! I probably have the same line disconnected as well, I will be taking it apart later today or tomorrow.. Thanks for the pictures..

saer1one

Problem solved..! A small metal pipe that comes from the front driver side by the headlight and connected to a hose by the air box was completely off.. Took it for a drive and it idled at 900-1k rpm.. That explains my 13 mpg average as the car was taking in more air to compensate for the vacuum leak ..

Lessons Learned:
Please be careful when removing air box and make sure ALL vacuum lines are connected before reinstalling air box ..