Hi, I am having problems with low power on my 1992 300se, with the m104.990 3.2 engine, the version with the distributor/rotor system and one single ignition coil.

It seems to have enough power and responsiveness at lower rpms, until about 3500, but anything above that and it is struggling to increase speed/rpm. It does rev until 6500(or whatever the redline is) but seem to have a hard time doing so, as if its pulling a really heavy load. Also sometimes it will stutter at around 4-5000 rpm (as if there is a dead spot) and sometimes not.

I have tried to engage neutral while driving, and rev the engine, it does not want to rev freely, takes time to reach the rev limiter. And if you keep holding the pedal at full throttle it will take approximately 2 or 3 seconds to reach the rev limiter again. Sometimes it won´t even be able to reach the rev limiter, but the rpms stop at around 6000 and fail to increase.

The spark plugs have been changed, the ignition wiring seems good and measure good resistance, except one having just a bit lower ohm´s than all the others. Rotor and cap seemingly looks ok, but could have done replacing. Injector/MFA wiring harness replaced with good healthy wires. Throttle body wiring is in good condition. The fuel pump vacuum purge valve working, and cleaned.

Tried driving with MFA disconnected, its even more sluggish.
Tried driving with the camshaft timing clutch (variator?) disconnected, and the engine sounds dramatically different, with somewhat difference in engine power.

Exhaust smells a bit rich I presume, but I´m no good at telling the difference between a rich or lean exhaust fumes . Although I know that an EFI vehicle should not smell this way

Does anyone have any suggestions?

Thinking about whether the o2 sensor can cause such poor performance? And if anybody can guide me to where the connector for the o2 sensor is located?

Any help is appreciated!

 

No one that can guide or have any ideas?

 

O2 sensors are easily found if you look under the car or by the rear firewall.
Can't miss it.

Have you changed your fuel filter before?
What about checked for clogged EGR valve/tube?

I had a m104 that was clogged badly causing performance issues.

 

Thanks for some pointers, I'll have a look underneath and follow the cable for the o2 sensor to find the connector.
Fuel filter is replaced some months ago.

As for the EGR, I haven't really checked it, but I did find that this engine has an auxiliary air pump fitted, however I am not familiar with this setup.

Are these pipes related to the EGR system, or is it only the air pump?

 

That metal tube in between the exhaust manifolds is it.

You will need to 'roto-rooter' it if it's clogged or take the whole pipe out which will be more of a job.

Does your car have the diagnostic button in the hood near the firewall?
You press a button and it will blink codes.

You need to check for codes and write the number of blinks down to determine which it is.

 

It doesn't have any button, but I did make a simple diagnostic tool with an led to blink error codes. There were many codes, due to failed wiring harness (which is now replaced & codes cleared) guess I'll have to try to read the codes once again.

I'll also try to clean out the pipes👍.

Do you have any idea where the ignition coil is located? Or is the coil integrated in the EZL?

 

Hey did you figure out the solution? I’m also having the same symptoms. I wanna try cleaning my purge valve but I can’t find it. Where is it located? Thanks.

 

So I have disassembled the EGR assembly and cleansed it thoroughly. There was a lot of soot, (well actually we could call it charcoal ). However the problem is still present.

The purge valve is located on the drivers side in the engine bay. You have to remove the large plastic cover on that side. (should be the same side as the fusebox/brake master cylinder)

You can feel it "ticking" when the engine is running. If its not ticking, you can remove it and try to spray som brake cleaner or WD-40 inside to get it unstuck. (I also had to tap mine carefully with a rubber mallet, but it eventually started ticking again). A tip is to use a 9volt battery on the terminals once you have it dismantled, to check whether it is working or not.

 

Is it under the cowl that runs across under the windshield or is it the plastic cover with the turn style push pins?

 

Its underneath the plastic cover with those turn style push pins

 

I've cleaned it and I still have the same issue. I did hear it make the tapping sound so I believe it is ok. Thanks for your help anyways.

 

Out of nowhere, suddenly the horses found their way back. It stood still for about a month and was even slower, incredibly low on power the first day I used it again. However the next day, it somehow had an amazing responsiveness, and all its power back. It´s been good for about a month or so now. Sometimes it seems to have a littIe less power, but the difference is minimal. Tested 0-100 km/h; roughly 10sec, whereas earlier it would have problems reaching 100km/h. factory numbers state 8.9sec for 0-100, so its not to bad for an almost 30 year old vehicle.

I suspect it must have been some sort of clogging somewhere. Either it must have been clogged cats or the fuel line. Next step: check the cats (whether anything still remains inside or everything is in bits and blown away) and measure fuel pressure/amount.