cabruce64

Hi,

I recently had my car tuned by Ramspeed Australia this was a Stage 1

1. ECU Tune
2. IPE Headers with high flow cats

After having this tune, the engine "apprears" to be missing. It only does it when you are off the throttle and gently get back on it. For example if you are coasting down a hill and just feather the throttle, there is an instant of "power loss" and you can feel the whole drive-train move "like a clunk". Say you are going slowly around a round-about and then just touch the throttle, again "miss"! It doesn't really do it when it's cold and seems to do it less in comfort mode.

What's interesting is that if you punch it, it never does it. So never under load.

Vehicle Details
2009 C63
90K miles
98 RON

Does anyone have any idea what could cause this? I took it back and they spent nearly 2 weeks trying to "fix it" getting new tune files back from Germany - they improved it a bit but its still there and does it frequently. It's kind of driving me nuts and i'm almost at the point where i will roll the whole thing back to "standard"... which sucks because it's got so much more pull with the headers and tune!!

Also the car is not throwing any codes. I took it back to mercedes and got them to run their diagnostics - nothing.

Any ideas?!?!?!

Thanks,

Craig.

NotABaller

Happens to me too, there is a little jerk when getting back on the gas. I think this is normal and just due to throttle plates opening/closing and breaking the vacuum when you get back on the gas.

bmroxm5

I heard of a similar issue that was tune related, perhaps get them to flash back to stock and see if it still does it (ignore CEL that will appear after 1-2 days)
Or get a second opinion from another reputable workshop.

Diabolis

Hmm.... well, I suppose there is a possibility that it could be caused by ECU interference rays from Mars.

That's like asking "I wanted to have better vision, so I found a little camera lens and glued it to my eyeball. Now my eye hurts. Any idea what could cause this?"

cabruce64

Whilt it's good to know that some one else has this problem; it's by no means NORMAL! LoL

Even the tuners said the infamous "we haven't seen this before" funny thing is the behavior changed as they fiddle with the tune...

cabruce64

They did suggest getting the car flashed to the latest software and then they can re-submit the file to Germany and try again. We haven't done this yet but i think i'll do it. Of course Mercedes are the only ones who can do the software update so its $400 for that little service.

Frankly i was interested in seeing how many ppl have encountered this problem and if they did get a fix before "having a guess"

Thanks.

cabruce64

It would probably help if you stepped away from the keyboard.

loungn14

It does sound tune related. And $400 to flash to stick yikes

if there is anything we can do to help let me know

Merc63

Change o2 sensors out.

cabruce64

Educated guess or speaking from experience?

I figured maybe something has gone slightly out of spec but not enough to throw a code....

Merc63

Highly educated guess and experience.

bluejae

just guesses..

check o2 sensors

check air filter to see if really dirty or something blocking

Diabolis

So - let me get this straight. Car worked 100% fine with the OEM tune. It was then tuned - and not by EC or another well-respected tuner - and has since had the described driveability issues. The ONLY change that took place was the tune, yet you're barking at O2 sensors and air filters? What am I missing aside form the obvious large hole in the brain which seems to the case with most of you here?

bluejae

well in my case, i had my own issues which for the longest time i assumed it was the tune because i noticed something right after a tune... and no matter what i did with the tune with the help of the tuner was able to solve it... it wasn't until much later i discovered it was a combination of some bad o2 sensors and bad air filters... after that the tune that i had thought broke my car was working perfectly... so even though it may not be the case for the OP, i don't think it would hurt to at least check the air filters which only takes a few minutes... it's a 2009 and who knows what filters he's running and how long it's been in there... the tune and headers may have just amplified something other than power before the mods... if it helps the OP then cool, if it doesn't, then check it off and move on to something else...

Merc63

Says he installed headers, did he not? Usually headers cause o2 problems after install. Where are the o2s installed on the headers? Is there any leaks up stream?

These cars run closed loop 24/7, if the o2s aren't reading correctly it will cause fueling isues like this. The tune says to target a certain afr, with o2 feedback it targets that. High mileage combined with a tune and headers can require new o2 sensors. I change mine out every to summers just to keep them fresh.

Faulty o2 sensors can read plus minus 20 or 25 pts before tripping a code and still be causing part throttle issues. Also, slip fit headers or leaks up stream of the o2 can cause part throttle fueling issues as oxygen seeps into the exhaust stream.

Never under estimate the importance of perfectly functioning o2s in these cars.

Merc63

Oh ya, pull the spark plugs and check them out for fouling. If they haven't been changed in a while, change them.

cabruce64

Hi,

Thanks for the ideas with this... i've been away on business for a while and then with XMAS and New Years, well there goes the year!!

Merc63, thanks for your comments/ideas (and bluejae) the interesting part is that the tuner had also suggested that it may have been a pre-existing problem that has been magnified by the tune. The fact is before the tune, if i got off the throttle there was a very subtle movement in the drive train that you could feel it, but nothing like now.

In any case i'm going to replace the sensors and also throw in a new set of plugs (its due for these anyway).

Will see how we go.

Thanks again.