Cold performance awesome, hot performance sucks
 

So what would make the cars throttle response sluggish once warmed up and all?

Is anyone else experiencing this on their C36?

• Snappy shifts when cold
• Fantastic torque when cold

• Once car warms up, shifts are delayed and very soft
• Accelerating is significantly slower
• Once moving, flooring the pedal creates a LOT more noise, I see revs go higher, but the car takes its time

There is definitely something wrong there.
It could be a million things really, but lets start off with the obvious.. Do you have a genuine Bosch MAF? Fuel filter ever replaced? Correct premium fuel? Air filter not clogged?.... Any codes??

Yes, brand new.

500 miles ago, genuine German unit.

93 and only from Shell.

Nope. Looking good.

Obviously this is where the real issue is. 2 codes. Just came back from diagnosing this:

1. P0327 <- Knock sensor
2. P1341 <- Variable timing solenoid

1) There are two knock sensors on our block. Its an inline engine, so both are bank one. I replaced the one at the front already, since this is the second time I got the code, time to swap the one closer to the firewall.

2) Not sure about this one. Makes perfect sense, that is exactly what it feels like, a slow\stuck camshaft profile. I did a few searches but nothing constructive came up. I tested the wiring to the solenoid and the resistance is just within spec.

Yeah definitly sounds like number 2 too me.. Something to do with your variable valve timing...?

I had this problem when i first got my c36. Revs shot up when I stepped on it but no significant accel power to match the revs???? Right?

When I took it to my shop the solution was this:
Replaced camshaft sensor
Replaced the Electric adapter
And did a massive service to the Transmission. Replaced the transmission plug

Also ALL fluids in the engine and transmission were flushed twice

After all this I never once experienced the problem I was having. And it sounds like what you have described was EXACTLY what I was struggling with. Horrible performance when the engine warmed up, GREAT when cold

Hope this helps. Good luck. BTW if thats your engine it looks great! (is that another look for the 43 engine without the plastic covering?)

is there a shudder at take off? your tranny fluid could of become de-polyermerized, when it is cold it has more power than when it warms up is a tell tale sign. Changing your tranny fluid would solve this problem

check ur wire harnessss , when u start getting repeated codes, it can mean ur harness is shorting. and check quick.

First of all, thanks to all of you for the suggestions!

The wire harness has been replaced on this car only 30K ago. I am aware of the problem with the biodegradable units.

No shudder. Transmission has been drained, refilled with Febi Bilstein fluid I got from the dealer. Filter and gasket were also replaced. Mechanic told me the fluid was in really good condition anyways.

Camshaft sensor is brand new.

What is this electric adapter?

I too have the same deal going on, complete with the occasional knock sensor CEL too. The hard shifts when it are cold are due to the way Mercedes made it so the car holds the gear longer to get the engine into higher rpms, and warm up the car to optimum running temperature faster, and I think because of the higher rpms this has to do with the harder cold shifts i f I am correct.

Could the performance issue have anything to with the Catylitic converters or the O2 sensors because some Cat sensor came up in the scan I did, just not as DTCs.

I'm interested in knowing what the electric adapter is too.


-Chris

Damn, really?

Got the car up in the air today, swapped the remaining knock sensor out. Waiting on the code to come back.

When the code came back today, it was only for the knock sensor, not for the variable timing solenoid. I tested the solenoid resistance anyways, and its a little too high @ 9 ohms. Should be 4-8.

In any event, the issue is caused by ecm retarding the ignition timing, presumably to prevent damage since it finds knock sensor faults.

Will report back.

Im embarressed to say I am not familiar with what it Really is either...

I remember my mechanic mentioning it was replaced and I didnt question what it was or what it did. When I went back through my log book of service records I read that along with other things it was replaced specifically for this "problem" I was having. I will get back to all of you on what it is when I stop by his shop one day. I'm sure your merc mechanic will understand what it is or what it could be. Sorry for the confusion.... But it worked i guess :)

how old are the cats on the this car, could they be on the way out? CATs usually when they reach the end of their life, and are almost clogged up, they will checke the car the hotter they get. and a choked engine can show miss fires.

Jump- did this happen before you got the tune ?

Since most tunes are spark and fuel enrichment it will expose weak spots like 02 sensors, knock sensor and as Jayrasheed mentioned clogged cats.

A great test would be to try someone elses ECU thats stock and see if it does the same thing.....easier said than done though as you might be the only one in CT that's got a running C36.

Sounds like your car almost goes into limp mode when hot....it doesn't have one, but the ECU will retard timing to protect the motor when that knock sensor sez.....oh no you don't mister :eek:

Keep us posted regardless.

Hey buddy I had the same problem change your timing chain guides, you car will transform! and drive like it does if not better than when its cold.

Slight threadjack here.....but your car looks sweet, can you post pics of it ??

IIRC, the guides are plastic, so if there is wear, they most likely expand when hot and cause the chains to have some resistance.....but wouldn't that make a noise thats very audible ?

When I opened up my engine and saw the guides, one was cracked straight threw and about to break into 2 peices. Thank God I opened up the front part of my engine and changed it! :eek:

Very interesting. How did you guys find out about the timing chain issue?

I am back at baseline tune, I was wrong when I thought PowerChip flashed me to advanced timing. I will be sending in the ECU again as soon as I sort this crap.

Order timing chain guides right now. Easy job?

Okay attached are the relevant pages from Bentley book. How did you guys service this one, I can only see a way to take off the top timing chain cover and that only allows access to the top chain guide it seems. Did you replace all 3? How did you do this?

http://farm5.static.flickr.com/4003/...f8b14fdf_b.jpg

http://farm5.static.flickr.com/4036/...9053345e_b.jpg


Looks like I need to replace 2, 5 & 12, but removing the top timing chain cover only allows access to 2. Hmm.

Got the parts.

So how did you guys do the lower 2 guides?

When my mechanic did the full headgasket, he also did the timing cover gasket and opened up the whole FRONT of the engine, from the top, right down to the oil pan. Once you do that, you'll get access to all the guides.