503C43 ////AMG

This was a key piece of info that was omitted from the previous posts. I am betting it was the MAF...

GT-ER

The used maf ( which I thought was new ) fixed every drivability issue yet is was still lean. When I find out it was used then my brain started ticking again so I ordered a brand new one. I've talked to just about everyone and the car was scanned by various people and no one can figure out what's wrong but most have said that the mafs are really bad on these cars...so in goes a brand new one.

moosejaw

Dude that's crazy.
My C32 dynoed 307 hp stock????

What about injectors/ Are they flowing?

GT-ER

Seems like it. The car idles great and drives great. I would have to remove them and send them off to check to be sure but for now they are low on the list of things to do.

After installing the new maf I'm going to re dyno it. EC said that they can tune out the running lean part and already uploaded a new file on the car so we'll see what happens.

blackbenzz

+1. I wouldn't buy a used MAF

MBfinatic

compression test needed!

GT-ER

I put in a brand spanking new oem maf today...now the car feels SLOWER! Like, 50whp slower. It won't even budge the tires from a roll. LOL...this car is freaking crazy. I told him to leave the battery disconnected all night to see if it gets better. I disconnected the battery for about 20minutes but I don't know if that's long enough to clear the adaptation values.

I honestly doubt it's a compression problem since the has gone from being a snail to being somewhat quick ( although still underpowered ) to being a snail again...with new parts!

I hope tomorrow it'll feel better.

Shifter

Have you checked your reference voltage to the MAF? You should have a 12v, and whats important is a STRONG 5v reference. Not 4.75, but 5v.

GT-ER

No, I haven't. What pin is it?

Shifter

Well I don't know ur production date, butacording to this diagram pin 3 is ground, 4 is your 5 v reference. Also check for the 12v. Just check each pin to ground, you won't hurt anything. (with key on)

GT-ER

Copy, will do. Next week.

Dknowz

So what happened did you figure it out?

GT-ER

It's not next week yet. I hope to have the car on monday.

Das Geld 2

IDK how I stumbled on this thread.

But it's crazy!

GT-ER

I checked it today...4.99V.

I also did checked the CEL and it had bank 1 system too lean and bank 2 system too lean. The MAF is new and I can't find any vacuum leaks ( I even sprayed carb cleaner all over the place with no change in rpms ).

I checked the long term fuel trims and they were at +22 on both banks.

Thoughts? I have the car all day tomorrow so I can play with it.

kent426

Bent exhaust valve comes to mind. Looks like a compression check may be in order.

amgalex

HAHA
this is so reminding me of my e55, i had weird low power issues which were related to car running lean
I did so much messing with it over the last 2 years and still am working on it, it made my head spin
changed MAF like 4 times, new plugs, wires, distributor coils, re-flashed ECU, resealed ECU (water condensation was noted after rain), ran e85 for a week to clean things out, installed IAT controller for manual temp control override, flushed Injectors, flushed fuel rail, ran car with o2s disconnected for weeks to bypass negative fuel correction, new egr , all new gaskets/seals, vacuum leak test(smoke machine)

my low power issues would be resolved by ECU reset(battery disconnect method), difference was night and day from like 6.2 0-60 back to 5 sec where it should be, but after 2-3 days power loss was again apparent and was confirmed by monitoring o2s ,lean condition again .I got so tired of disconnecting my battery all the time to temporarily fix the issue
by monitoring through obd i could see fuel was actual being pulled out when it was needed (negative corrections) up to -25% pulled at WOT in open loop
About 6 month ago issue seemed to have gotten a lot better, no more negative fuel correction, car ran fine but going lean only from 60% to 80% load after 80% would be just fine. Fix to this lean spot for now has been a reprogrammed MAF ,, (still trying to work out details, need Wide band o2 monitoring to see exactly where AF are but there is definitely no more big lean spot now and car drives great

in last 6 month i have done, reflash ECU, IAT mod, Flushed fuel rail by squeezing the nipple on the front of rail and letting gasoline pour out, ran e85,

I would suggest flushing fuel rail, easiest thing to do (it was suggested by a MErcedes tech , he said 'seen similar symptoms that were related to dirt being built up in a return-less fuel system like ours where front part of rail would get dirty and clog up ' worth a try for you and easy to do
good luck

GT-ER

Why a bent exhaust valve? Car drives fine. Both sides of the engine seem to have the problem so in any case it would be more than one valve. I'll check compression today.

GT-ER

Haha...damn.

Has anyone heard of a cracked intake manifold? Maybe it's taking air from below ( my carb cleaner experiment won't work if it's taking air from the valley ). Food for thought?

Robert AMG

iTrader: (1)

GT-ER try to disconnect the front O2 sensors and test drive it.

GT-ER

I actually have brand new 02 sensors in front of me...I'm swapping them out.

I can't really see the 02 sensors being a problem because what are the odds that BOTH are bad, but maybe the maf being bad from the get go ruined the 02 sensors? Who knows, but I am actually going to install new ones anyways since the car has almost 100K on the oem sensors.

c32used

Interesting....it sounds as though there may still be issues prior to installing headers...OP I see your dilemma but did you dyno before and after each mod? Also was same dyno used? Maybe your mods are killing your HP/TQ? I've had a past issue where my car lost power on mid to high down the track found out it was some spark plugs not gaped correctly triggering CELs. You may need to go backwards and see if any mods have issues.

Shifter

What isyour mixture self adaptation at idle speed?

GT-ER

I dynoed before and after on the same dyno a week apart. Before was 289 and after was 297 with LESS torque than before. The car has the basic mods other people have and they all have well over 300whp so I dunno what to say.

+22 on both banks.

In about an hour I'll have the intake manifold off the car...I'm going to check it and all the vacuum hoses off the car. It's an easy enough task.

mikekuriger

did they do the "tune" on the dyno? Or just plop in a tune that worked on other cars? Sounds like he needs a real tune since it's so lean. No 2 engines are identical.