joe-pilot

Hi All.

I have read numerous threads about the same sort of problem but no definite outcome.

I have a 2003 C32 AMG , and about a year ago I noticed the power just wasn't there anymore.
I am getting a check engine light, codes are cat working below efficiency, and misfires (both banks). I have checked the cats and they seem fine. My mechanic thinks it could be a MAF (we don't have one on these cars). What we do have is a Manifold Absolute pressure Sensor and an intake temperature sensor. I have bought both from mercedes and right now I am trying to find the location of the MAP sensor...

Anybody know where this is located and what the other causes could be if this doesn't work.

thanks

Lenin

What were the codes and why do you think that the cats are fine? How did you inspect them. The one of the sensors is on the lower Y-pipe and the other one is in the same area. You may be able to feel your way through if you have small hands. Otherwise you would have to take the TB off.

joe-pilot

Hey Lenin

codes were misfire.. they were random on both sides of the engine, and cat working below efficiency not sure the code numbers right now.

we had the car up on the lift. temperature of cat and pipes on both sides were good, cat had no rattle to it and no signs of overheating as seen with a failed Cat.

I found the intake absolute pressure sensor.. to get to it looks like I have to take off the throttle assemble as it is located at the back of the engine below super charger.

Lenin

I would go slow and check one thing at a time. First, just in case, check you IC pump. It does go after sometime and may cause the loss of power. Then clear the CEL and the stored codes using the STAR system and see if the codes return. i remember Jake or Jerry from Eurocharged having missfires and it took a long time to pin it to a bad cat. Also you should change you sensors. The car is 9 years old. It's time. Depending on how many parts you take off, see if you can change IAT, MAP and CPS sensors. And find a mechanic that knows that a C32 does not have a MAF.

joe-pilot

Clear the codes every time I go in and they return within a few hours. I have a new intake temp sensor and the intake pressure sensor. Will change those on the weekend.. just waiting on a new gasket for the throttle body from the dealership.

I think the IC pump is ok, when I shut off the car it runs for a few seconds... but if this fails it will be the next to get changed... at this age i don't mind upgrading a few parts...

I will post some pictures next week for reference so people can see where these sensors are.

Lenin

Next, I would bite the bullit and remove the downpipes and see for yourself the condition of the cats. From what I remember, the Eurocharged car had some crap from the cats blocking the exhaust gases. Search for that thread. I think it had "misfire" in the title.

razormb

I just went through a similar issue. Started having misfires and would end up in limp mode under WOT. Eventually lost all power. I thought the pump was bad because it wasn't turning on so I replaced it. The new one wouldn't turn on either (I can easily check thanks to the C3 reservoir and see if the coolant is flowing) so I decided to test the pump. I did this by jumpering the fuse in the rear sam and the pump turned on immediately. I next tested the old pump with 12v and it worked fine to. In fact, it turned out the whole IC system was just fine.

Next I decided to check the cats; I recently had the secondary cats and resonator removed where the mech. discoverd some honeycomb breakdown on one of the cats. I was hearing some raspiness (sounded like a diesel) but I thought it was normal and was the result of the mod. I decided to have the primaries pulled and replaced. Turned out one was completely blown through and the other had broken honeycomb. As soon as I had them replaced everything was resolved and the power was back! My IC pump turned on right away as well which tells me the ECU immediately shuts that system down when it detects a problem with the cats. Up to that point I received no indication of blown cats other than the noise and some foul smell from the rear. Not sure if I had lazy O2 sensors and why I received no indication of the cats failing so I had all O2 sensors replaced.

Moral of the story is it could be your cats failing which is why your losing power. Of course why the cats failed is another story (running to rich perhaps? to many misfires? fouled o2 sensor?). I'm still trying to figure it out. If the root of problem isn't solved, eventually they will fail again.

joe-pilot

Replaced the temp sensor, it was a mess... No noticeable change guess the cats are the next thing to get checked. My mechanic says he can take them off and clean them?

alkrstev

Is there any updates on this? I got some power loss too and wondering if my cats are fried too.

joe-pilot

I have noticed a little better performance since the temp sensor change but not what it was. Hoping to get the cats looked at shortly... will update.. I miss the fun car it was..

c32kompressor

Correct me if I'm wrong, but if the cats are bad you should be able to tell by a fume odor from the exhaust. Or a rattling sound coming from under the car where the cats are.

c32kompressor

Correct me if I'm wrong, but if the cats are bad you should be able to tell by a fume odor from the exhaust. Or a rattling sound coming from under the car where the cats are. For misfires check your coil packs. Find out which cylinders are misfiring and move the coils to working cylinders and see if that good cylinder starts misfiring

c32kompressor

Also, a clogged cat will cause random misfiring

mdavidian

Joe-pilot,
Where are the sensors? I bought both thinking I could change them when I did my plugs/ valve cover gaskets, but could not find them. I think I see the TB (where the air intakes come together in the back of SC?), but cannot see a way to get this off. Screws are on the back of it, and it looks like there is no way to get a screwdriver back in that tight space.

joe-pilot

mdavidian
both sensors are under the super charger. The temp sensor is at the back right under the air intake. I had to take off the intake to get at the temp sensor. You will need to order a new gasket before you take it off. The pressure sensor is further forward and requires you to remove the larger section in front of the throttle body before the supercharger. it is a little more difficult to do and also requires a new gasket. Luckily both gaskets are fairly cheap from mercedes

mdavidian

I see a black plastic piece at the back of the top of the engine where the air intakes merge. Is that the throttle body? If so, how does it come off? The pressure sensor is in front of the SC or just between the TB and SC? Sorry for the silly questions, the past few weeks have been a trial by fire as it is my first time working on this thing.