Tzvetan

Have rough idle and no accelerating and power. Starts fine but immediately goes to rough idle. No any check engine codes. What could be the problem?

Nitsuj

I'm no MB expert, but I can guess until one comes along. I've never had the problem myself, but I have seen others ask this same question. I believe the most common suggestions to check are catalytic converters, and vacuum lines.

Tzvetan

Thanks. I already sprayed around with carburetor cleaner for possible vacuum leaks. but had no result on this. This started bad for few days, but the run got improved after the engine warmed up. Today stays on the same rough idle and no accelerating and power even with full warm engine. The car even barely moves and is shaking. Starts instantly, which makes me thinking it is not from the plugs.

Nitsuj

I think spraying carb cleaner would isolate an intake leak, I don't know that it would help with a vacuum leak elsewhere in the system though. The complete lack of power would lead me to guess the cats being clogged, but I'd wait for a more informed member to chime in.

Tzvetan

I read in different forums that bad cats may lead to such problems, but I just wonder how this may create such a big impact on the engine, I will try to disconnect the exhaust before the cats and pray that this will be the cause.
Appreciate very much your advices.

Nitsuj

Simple, it creates a big impact on the engine because it's clogging the exhaust. The car can't run if it can't breathe, and by clogging the exhaust, it's able to inhale, but not exhale. All that air it's sucking in has to have some place to go after its mixed with fuel and burnt. Get under the car and tap on the cats (gently)with a hammer. See if they make a rattling sound. It's not a definitive test, but often the innards of the converter break up and clog it. When this happens, you can here it rattle when you tap on it. Again, not 100% definitive, but it's the quickest and easiest test and a good place to start.

Tzvetan

Thanks a lot again for your help. I will do this check in the next hours. Will also make a video how the engine works rough and the response when I try to accelerate. Some time when I push it harder PO300 and PO301 codes come /cylinder 1 misfire/, but only when I put too much pressure on the throttle. No other codes.

Nitsuj

My guess is it's going to be the cats then. I've seen other forum posts of people throwing misfire codes, it eventually leads back to the cats.

Tzvetan

Will follow your suggestion to hear what noise will come from the cat. Then will try disconnect the exhaust pipe before the cat. Then we will definitely know if the cat is the problem. Thanks!

Tzvetan

I knocked both cat convertors, but did not hear any noise like something is moving inside.
This model is with two parallel convertors, one for each tree cylinders.
I spoke to a friend of my son - 92 years old German, who runs MB repair shop for many years and he said "MAF sensor". I actually cleaned the sensor very soon, but he said "replace it" He also said that 97 MB does not have codes for MAF censors. I see carparts.com sell replacement one for $ 39. http://www.carparts.com/details/Merc...b6-2ea54d111f0
What do you think?

Nitsuj

MAF would explain the codes, and it's a cheap fix. I'd try it and see what happens.

Tzvetan

Well. With the new MAF censor works the same. Rough idle and stays at 1200 RPM. Even foes not want to react at any attempt to accelerate. just stays and runs like this.

Nitsuj

I think you're going to have to bite the bullet and consider you got a bad cat.

Tzvetan

They are two cats. Each connected to 3 cylinders. Must be both clogged? Engine is not throttling at all. I will change the fuel filter, but doubt it is the problem. Maybe the throttle body.

Tzvetan

I changed the fuel filter, but no result. Looking inside the throttling body I see the flap is not reacting when you try to accelerate. engine is inline 6 and the body is difficult to reach. will try manually to open a little to rise the RPMs. My logic makes me thinking that the fault is around here. In other forum for similar problem mechanic was suggesting the fault between the potentiometer and body. The only difference is that in their case PO120 code comes up. I have nothing.