I'm still not smelling bad cats here. The fact that the check engine light comes on when it's running it's worst tells me this is an electronic issue (CIS-E or EZL) not mechanical.
Regards, Eric

Gush

How can I check the codes it has stored?

I would have to rule those out as it idles with no problem. Also it usually runs pretty decently when I first start it and drive it. Gets worse once the engine warms up.

Also a cat is not mechanical.

The reason I sniff a cat is the reason that once it warms up it runs like total ****. I know that a cat takes a few minutes to warm to operational temperature. Thus causing the issue when the car has been driven for a mile or two.

Please let us know when you find out what it is.
Regards, Eric

If the symptoms appear only when the motor is warm, perhaps it's time to also check the main temp sensor, the one that supplies resistance signals to both the CIS and EZL.

Or the vacuum line to the EZL?

I just remembered that cars with plugged exhaust (this would include plugged cats) don't pull good vacuum. How good is the vacuum on this car?
Regards, Eric

I have an 88 300te. When I first got the car it would idle like it needed a tune up so I replaced the rotor, plugs and distributor cap, still ran the same. I found that there is a fuse behind the battery compartment that is a safety from mercedes that if anyone jumpstarted the car the wrong way this would go. After the fuse was replaced, my car idled without any problem. There was a plastic divider behind the battery I had to remove to access the fuse.

wheelsfan, that fuse was atop the OVP relay. If the solder joints inside the OVP relay crack the engine will run/idle rough too. On our 1995 E320 the OVP relay buzzed when there was a problem with it.

If the CEL comes on, YOU NEED TO PULL CODES
before trying anything else.

The OVP is a prime suspect for this type behavior

See, the low octane gas you put in caused a cold solder joint in the OVP to ,,,:rolleyes: (kidding) seems to me the gas had nothing to do with your problem, unless it was bad gas (unlikely)

I have seen problems like no start, or hard start, or starts and runs then all of a sudden dies all caused by the OVP relay. (One 190e I parted saw the better part of an ax because the PO couldn't start the car, I replaced the OVP relay and started first try)

It wouldn't hurt to ensure that the electrical contacts are clean too. And that there is no corrosion on the ground wires.

The symptoms of a broken temp sensor are slow starts and poor idling while the engine is cold, not warm. I can tell you this because I broke the sensor and the difference was immediate and noticeable. I got a new one and it went back to normal :cool:

Cheap spark plug wires can cause poor running. Did you use Beru wires or whatever was sitting on the shelf at the local auto parts house?

What did this turn out to be?
Regards, Eric

I just got back in town and thought that I would check a few things. When I started it, it was a little hard to start. I just primed the fuel system and it seemed to help. As soon as I put it in reverse it dies now. Also with it in park if I tap the brakes the ckeck engine light flashes. When I put it into reverse the check engine light comes on and it dies. I didnt try to go to drive. I am thinking that this may be the OVP relay now. I just went out and tried drive and it was fine. Also when I tap the brake pedal I have to let the car move a little before I tap the brake to make it stop abruptly then the check engine light comes on. Any Ideas?