cmpcpro

Hey guys does anyone ever notice a surge when coming to a stop like the RPM almost stumbles and then picks back up and you feel the car push forward? I've got the 722.6 and this is a new trans and it did it with the old one too.. although the valve body was in both it was refurbished from Mercedes about a month before the tranny rebuild. I'm wondering if it may be unrelated to the tranny or if it's putting it into first at the wrong time? Anyone notice this? Also have a new TPS too but I notice my idle is sometimes high like 7-750 then sometimes 600

EDIT: so I don't think it's the tranny possibly, I think when going very slow and turning the wheel once in a while the rpm stumbles and then catches itself and that's what I'm feeling. Usually it's minor but if it drops a good bit then the RPMs go up higher and you notice it push a little through the light braking pulling into a parking spot.

GatorMB

Bro,
That could be a lot of things, plug wire, vachume line cracked, Throttle sensor/actuator, PS pressure and position circuit.
Make sure all the battery connections are clean and tight. A SAM might be acting up.
Any codes in the ECU? CEL

Cheers

cmpcpro

No I have no lights. Plugs and wires are new, abc/ps pump was just rebuilt by Mayle. Also the TPS is new as well.

new55

i have noticed mine does that rarely,,, annoying pulling into a parking space but does not happen enough to be concerned - i thought it was tune related somehow but if yours is stock then its something else -- i have no codes or other issues (that i know if )

cmpcpro

Glad to hear.. mine is bone stock with many many new OEM parts on it and no codes so I don't know what it is either

GatorMB

The Throttle body or throttle plate likely has some varnish coking up the natural idle position.
The varnish can degrade idle quality and delay throttle actuation. This happens to all cars and Mercedes.

The throttle plate must be removed and sprayed down thoroughly around the plate and shaft. Avoid getting carb spray in the electronic actuator motor.
You can open the plate with your finger overcoming the internal return spring.
Use an old tooth brush with carb cleaner and scrub until it looks new again.

New gaskets are reasonable from autohauseaz.com.

Hope this helps a few.

Happy Fathers Day Folks, Gator

cmpcpro

Thanks Gator! I cleaned it while it was on the car the other day and it was dirty so I pushed one way and it only went a tiny bit but enough for me to clean around the edge, then I pushed the other way and was able to get in there better but I concentrated on getting the black gunk around the edges of the butterfly and where it meets the barrel, I didn't shine a light or anything down there to see if it was dirty deeper down there because I thought the important part was where they meet when it's almost closed, was I wrong? Also does the supercharger have to come off to take the tb off? Thanks again!

GatorMB

On the car cleaning is risky only because the cylinders will get washdown from the solvent.
I am not sure about removal because my supercharger is not installed yet (soon)
If you remove the supercharger for deeper inspection service and cleaning. De-coke the bypass valve actuator as well.
The only other culprit I can think of is Factory ECU recall upgrades that affected engines @ cruise not idle.
I would let it get worse enough to cause a CEL instead of throwing parts at it but thats me.
A STAR C4 datalog would show some inherent information but a weak ignition coil connection or similar scenario would lead one into many diagnostic tests and labor.
If there is no CEL have the trans scanned otherwise mechanical problems might exist.
I bet once you get close it will be a easy simple fix.

Cheers

PS: quick test spray a shot of carb spray at the brake booster inlet at the rear of the SC. If it changes engine pitch it needs re-sealing. (hunch)

carguyshu

the TB is easily removed with 4 bolts from the snout and the gasket is reusable. It is very possible you have a small vacuum leak that is random and not large enough to trip a code, but to cause idle problems. There is also a bypass throttle body located underneath the supercharger (to get to it you have to remove the charger) that does as the name says and bypasses the supercharger rotors and lets air in from underneath. A faulty or on its way out bypass TB could also be the issue. If you hook it up to star it will let you know if either is currently exceed spec on throttle position enough to cause issues but not enough to throw a code.

cmpcpro

Thanks carguy! I have noticed at idle the RPM is surging but it's so minor you can barely even see the needle budge.. the only reason I noticed it is because I have dog ears and I could hear the exhaust drone slightly change.. it's up down up down etc.. maybe 50rpm or so.. also I did have a vacuum leak once when the big hose behind the blower came off for the evap sys and before I fixed it once I hit the gas pedal in park and the Rpms went up to about 1500 and just stayed there.. could my gas pedal sensor be acting up? Also the y tube on the tb has two clips that hold it on one on top drivers side one on bottom pass side. Bottom pass side broke. It still seems to be on all the way though.

Hotsauce55

In my experience that is always related to a vacuum leak somewhere. My some of my older cars, spraying brake cleaner or the like will help you find the leak if you hear the idle change. I think you can get the system pressurized with smoke to find out for sure?

new55

i dont believe it could be a bypass valve issue if the SC only engages at ~3000 rpm (my understanding),, these surges are at or near idle --

cmpcpro

Thanks for the info, I do have a smoke machine but it wouldn't be pressurized. Where would be the best spot to hook it up to? Thanks

cmpcpro

Also, it seems to run better when I put a bottle of Techron in it or really get on it for a while as most of the time it's just putting through traffic.. and doing small trips.. I'm wondering if at 130k maybe the injectors should be replaced?

BoostedAero

Beat me to it! I had the stumbling from time to time, kinda had to make sure you were ready to lean on the brake hard. Techron every 3k miles fixed the issue, I have a feeling it has to do with the fuel side somewhere. Ever since I ran a bottle of techron through the system with my oil changes it hasn't happened since.... well and since I upgraded my injectors it hasn't happened once....

Things to ponder I guess. How long since your fuel system service interval? It may be time if you dont have a documented date/mileage stamp on it

cmpcpro

I haven't done anything to the fuel system besides replacing the sender, fuel pump and filter. I'm considering doing the injectors because while the Techron helps a good bit it's still not completely gone. I hear these 550 injectors are cheap but I usually like using OEM quality parts and plus the car is stock so no idea why 550s should be installed. Is there anything else that should be changed? Thanks!

MACEDON

Do your IAT sensor

and what Boosted said, run techron. Or even better run seafoam in your tank. Get two bottles and a funnel from walmart, drive to a gas station, pour both, fill your tank, and drive the car pretty hard if you haven't done it. That will rule out your fuel system and clean it up well.

carguyshu

you would put in 550s b/c 8 550s with harness converters are less than 1 oem. both are made by bosch, so there is no difference in quality. you would have to put in a tune to run the 550s. on both my e55 and sl55 I had a stock injector fail (both are 03 cars) and nearly ruin the motor in each. I replaced them all with 550s as prevent maint. and to give me more overhead for future mods (both cars were stock when the injectors failed)

cmpcpro

Thanks but I don't want to do a tune right now and that's $400 or more. The 550's are a few hundred on eBay and I paid $90ea or $720 out the door at the dealer with my discount for the MB injectors so I think I am about what I would be at for the modified ones plus a tune. Also 06 got newer bigger injectors from the factory so hopefully they corrected the issue.

principledchiro

I've a bolt-on mods 06 CL55 AMG, and now targeted to place on 82mm TB and 550 injectors. Have you Benz information supporting larger injectors for 06-up M113 motors?

builtbyfood

Have you checked the air temp sensor that sits under the air box? I just replaced mine and it resolved a lot of issues with bucking and smooth driving.

cmpcpro

Are you talking about the IAT sensor behind the throttle body on the back of the motor? If so yes it's a week old, OEM.

Thanks

Chris

builtbyfood

Yup, correct. Was it placed in the correct way for sure?

When your driving in sport mode and manually shift the gears up and down, does the car perform well, or are the symptoms the same?

cmpcpro

Yeah it's placed the right way.. and yes it even does it going in reverse. The RPM will dip or stumble and then catch itself. Also I noticed driving when I have almost no pressure on the gas pedal I will feel it occasionally feel like a strong gust of wind is hitting the car, yet if I just left off completely and coast down the hill it's fine.. I'm almost wondering if my gas pedal sensor is acting up..

MACEDON

My CLK320 used to do this, I never figured out what the problem was... any update?