W202 Complex Problems

[Benzica]

I have an automatic 1994 C180 (W202). It always starts, it always goes and it always gets me back home again. There are some problems though.

Here are the symptoms:
• It often fails to accelerate and seems to get stuck in one gear. Perhaps this is limp home mode?
• Usually a little bit slow to start. It always starts first time, but I have to crank it for a few seconds.
• It sometimes stalls. I can't find any pattern to this.
• The coolant light vaguely comes on and fades in and out. I have checked the Nissens Denmark radiator coolant and it does look a bit murky, but I don't think it would cause all this. It's not overheating.

Most of this is not as common in the cooler months. Whatever is wrong, it seems to be triggered by heat.

If it has a MAF sensor, I can't find it. There's nothing like that near the air filter.
The battery, alternator and voltage regulator all seem to be working the way they should.

 

[ajlsl600]

Try to find a good indy near you with older benz experience.

 

[LostKiwi]

Have you tested the battery on a battery tester? They can 'seem' ok but be near dead.

 

[Benzica]

Have you tested the battery on a battery tester? They can 'seem' ok but be near dead.

Thanks for the reply. No, just a multimeter. The battery looks okay and the connections are tight.

 

[Benzica]

Further investigation reveals a clicking noise. Could bad spark plugs do all this? I will get them changed regardless.

 

[C200 goblin]

I would say get your lambda sensor checked out and MAF. The coolant sensor also controls the mixture depending on engine temperature, if this goes bad, it would give all kinds of signals to the ECu and give bad fuelling.

 

[davemercedes]

If you update your profile with your approximate location, somebody will be able to recommend an "Indy" (Independent) near to you and really save you money if you have to have work done for these issues. There are quite a few forum members who are also Indys and they usually have "encyclopaedic" knowledge of MB models and their "foibles".

Good luck!

 

[rifiki]

I use to have a 86 BMW E23 with similar problems, I don't know if MB and BMW use the same Bosch fuel injection system.
On the BMW a new MAF fixed it with new plugs and leads.

 

[mattkh]

Thanks for the reply. No, just a multimeter. The battery looks okay and the connections are tight.

Please put up a picture, a birds eyeview, of the engine.

 

[Benzica]

Please put up a picture, a birds eyeview, of the engine.

This is the best I could do without making a shadow.

 

[LostKiwi]

No obvious MAF sensor there. Some cars use a MAP sensor to measure Manifold Absolute Pressure. If so that could be the culprit.
They normally sit downstream of the throttle body in the intake manifold.

 

[LostKiwi]

Ok looking at parts diagram it does have a MAF.
Item 5.

There are two locations it could be.

 

[ajlsl600]

Ca

Further investigation reveals a clicking noise. Could bad spark plugs do all this? I will get them changed regardless.

nt see clicking noise commin from spark plugs to buried to hear them. An arcing coil pack maybe. Or the fuel solenoid opening, closing.

 

[Benzica]

No obvious MAF sensor there. Some cars use a MAP sensor to measure Manifold Absolute Pressure. If so that could be the culprit.
They normally sit downstream of the throttle body in the intake manifold.

I found this MAP sensor (0 281 002 456). So this means I definitely don't have a MAF sensor?

What can I do to see if this is part of the problem?

 

[mattkh]

I found this MAP sensor (0 281 002 456). So this means I definitely don't have a MAF sensor?

What can I do to see if this is part of the problem?

Push the eletrical connector towards the sensor and then unclip the connector.
Use a socket to remove the bolt and pull out the sensor.
Take a picture of the tip of the sensor.
Use a carburetor cleaner/MAF cleaner spray to clean the tip of the sensor. Get it as clean as you can get.
Check the O ring and then reassemble.

 

[Benzica]

Push the eletrical connector towards the sensor and then unclip the connector.
Use a socket to remove the bolt and pull out the sensor.
Take a picture of the tip of the sensor.
Use a carburetor cleaner/MAF cleaner spray to clean the tip of the sensor. Get it as clean as you can get.
Check the O ring and then reassemble.

I couldn't get the electrical side off but I got the bolt off. When I removed the sensor, it came off with a loud pop and some gas escaped. I wasn't expecting that. Is that normal?

I can see some dirt but I don't have anything to clean it with yet.

 

[mattkh]

Well done.
Do clean it with a spray when you can.
From what I can see in the picture, the connector is not pushed in completely.

 

[LostKiwi]

Use carburettor cleaner or contact cleaner spray to clean it. Do not use WD40 on the electrical connector seal as it will swell the seal and make it impossible to reconnect.
When refitting use a smear of silicone grease on the green seal to make it easier to insert or remove later. Ensure the hole is not blocked in the manifold as it needs to be able to detect pressure variations. I'm surprised gas came out when you removed it as that should only ever be under negative pressure relative to atmospheric.

 

[Benzica]

Well done.
Do clean it with a spray when you can.
From what I can see in the picture, the connector is not pushed in completely.

I can see what you mean. I managed to get it off eventually and pushed it back in as firmly as I could.

I found this thing (012 545 24 28) and thought it might be related. I can't find out what it does. Seems that number was used for a few different parts. The wire going to it looks a bit damaged and the previous owner seems to have moved it. It appears like it should be bolted to the side of the engine, but it isn't now.

 

[Benzica]

I've seen big improvements after a trip to the mechanic. Changed the spark plugs, the ignition coils and redid some wires, although not the one I was concerned about in the post above. I've never known the car to function so well. I just took it around steep mountains on a hot day, with four people in the car and the boot full. It didn't struggle at all.

The stalling has gone, the acceleration problems have gone, but for some reason the long crank has remained. It doesn't start nicely. It takes a few seconds, giving the impression of an old wreck. I would really like to solve that, but admittedly it is a luxury problem at this point. It is well-functioning vehicle again, but starting it is just a bit embarrassing.