C36 loses power under hard acceleration

So far I've replaced the following:
Wiring harness
MAF Assembly
Coil packs and connectors,
Spark plugs/AIR/OIL filters
Oxygen sensor
What is exasperating is that this behavior only happens intermittently, there is no pattern nor common trigger that will help isolate the problem. I've had the car since it was almost new (17,000 kms) and regularly hits 255 kph with it, so no major problems with the motor.
Has anybody experienced this peculiar problem? Cure?
its at abt 3500 every time and then full power by 4000
now i think its the over load switch in the gearbox. Its more of flat spot on my car.
I see thats the one thing we both have not checked and on my new w140 500 i have a similar issue
but more sharp i was told its this switch that does it.
So if ur set to fix it try that.
I still hadnt had the time to go fix it my self so i cant confirm to u for sure.
the switch is on the left side of the gearbox has an electrical plug on it but i am not so sure u if the oil pan needs to be out for it to be changed.
Last i heard the part is abt 180 usd alone and then add labor.
If oil pan needs to be out change the oil and filter while ur at it. Gearbox oil that is.
Also, all the M104s tend to have that flat spot in that area but on the C36s its more pronounced. The only thing that really helped when I had the C36 was going to a lighter crank pulley. It didn't make it disappear completely but you couldn't feel the power loss anymore it just quickly accelerated through that dead spot to make it much less pronounced.
Its hard to make the M104s in general run perfect, they always have little issues here and there, thats just a part of their character they just don't really open up until 4000rpm.
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It doesn't feel like a flat spot, and it wasn't there when the car was new. I'll try to describe it. From stand-still I floor the throttle. In 1st gear the RPM will shoot right thru the 3200 rpm mark and slam into 2nd at around 6500 RPM, still climbing rapidly. Then at around 3200 rpm the climb will almost STOP, inching up then at around 3500 rpm there will be a burst of power accompanied by the characteristic ripping canvass sound of the 104 and shoot to 4000~4200 rpm at which point it will pause again
for a second then there will be another burst of power and it will slam-shift into 3rd at around 180 kph/6500 RPM. From there the climb to 260 kph/fuel cut-off is smooth and rapid. BTW when I baby the throttle there is NO hesitation.The thing is, it doesn't do this every time, although the flat spot at 3200 rpm is always present now, but not when the car was new. I have 68,000 kilometers on the car. I use RON 96 fuel + additive to increase it to above 98 RON. RON 96 is the best fuel that we can buy here.
Please explain further what are the symptoms of a failing Cam Position Sensor? I had a CRANK position sensor fail on my SLK 320 and the symptom was NO START when hot.
Last edited by BongC36; Oct 21, 2009 at 01:20 AM.
It doesn't feel like a flat spot, and it wasn't there when the car was new. I'll try to describe it. From stand-still I floor the throttle. In 1st gear the RPM will shoot right thru the 3200 rpm mark and slam into 2nd at around 6500 RPM, still climbing rapidly. Then at around 3200 rpm the climb will almost STOP, inching up then at around 3500 rpm there will be a burst of power accompanied by the characteristic ripping canvass sound of the 104 and shoot to 4000~4200 rpm at which point it will pause again
for a second then there will be another burst of power and it will slam-shift into 3rd at around 180 kph/6500 RPM. From there the climb to 260 kph/fuel cut-off is smooth and rapid. BTW when I baby the throttle there is NO hesitation.The thing is, it doesn't do this every time, although the flat spot at 3200 rpm is always present now, but not when the car was new. I have 68,000 kilometers on the car. I use RON 96 fuel + additive to increase it to above 98 RON. RON 96 is the best fuel that we can buy here.
Please explain further what are the symptoms of a failing Cam Position Sensor? I had a CRANK position sensor fail on my SLK 320 and the symptom was NO START when hot.
From what ur describing i am almost sure its the Overload thing, cause that’s what i have on my 1995 W140 but at 4000+ and 5000+ but still exact same thing.
On my AMG its just real flat spot and its annoying as hell.
To explain, the overload switch should only activate when shifting from first to second, i dont know if it activates from second to third.
Any way when it activates it retards the timing map to reduce power and save the gearbox. what i assume is happening is that the switch is messed up and its thinking your regular oil pressure in the gear box under hard acceleration is the shift point.
on my car when i drive very hard for a few min it develops a similar issue to urs at abt 5000rpm but still not as severe as ur case.
Ironic is that my car today is staring to develop same issues like bong here now i have mini flat spots at 5k rpms
AMS, I had my injectors cleaned and tested late last year. There was one whose spray pattern was dissimilar to the others and we replaced it ($$$!) but no significant change noted.
Last edited by BongC36; Oct 22, 2009 at 01:33 AM. Reason: spelling
yup and its gettin worse by the day. in third mostly u feel it and its f!@#Ing annoying
Guess ill be fixing it mid next week, if i get the free time.
waiting ur updates
This is on top of a 4-year old problem of a flat spot from 3200-3500 RPM that we had been unable to solve by MAF, spark plugs, coil, wiring harness replacement etc.
I read a post that the Electronic Throttle Actuator (ETA) or its wiring might be at fault so I tried opening the wiring lead going to the ETA. That darned insulation of the wires inside had crumbled to dust and the bare wires are actually touching!
I found an excellent post how to fix this in another forum and replaced the wires individually and I was pleasantly surprised that not only is the 1500 RPM trap gone, the flat spot or hesitation at 3200 rpm is gone as well! Not bad for a weekend afternoon's work

The MB dealership will not do this for you, they told me that they do it for regular Mercedes but NOT AMG engines. They absolutely refused to do it for me, I assumed that they were telling the truth as they had a paying customer there (me) begging to pay the $150 to get it done but they wouldn't take my money.
This is on top of a 4-year old problem of a flat spot from 3200-3500 RPM that we had been unable to solve by MAF, spark plugs, coil, wiring harness replacement etc.
I read a post that the Electronic Throttle Actuator (ETA) or its wiring might be at fault so I tried opening the wiring lead going to the ETA. That darned insulation of the wires inside had crumbled to dust and the bare wires are actually touching!
I found an excellent post how to fix this in another forum and replaced the wires individually and I was pleasantly surprised that not only is the 1500 RPM trap gone, the flat spot or hesitation at 3200 rpm is gone as well! Not bad for a weekend afternoon's work







