Have a problem with my 93 300E, it has a rough idle. When I stop at a stop light, the rough idle starts and the car shakes a little, but if I give it a little gas, it runs smooth. I took the car to German Motors, they called the next day and said it was the EGR valve. The cost would be $376.00, I said ok. The next day they called again and said the wrong EGR came in, there are two types for my car and it was the other. When the other comes in it will cost me $483.00. (I believe there is only one type for my car, the 3.2 engine has two)Got a call the next day and they said that the new EGR valve was installed and the rough idle is still there. They said it may be the Air Mass Meter and will install one tomorrow. Anyone here have any ideas before I go broke?

 

the EGR only works during part/full throttle. but if it remains open all the time, then the engine shakes in drive or neutral position.
it is the same as vacuum leak from intake manifold.

the air mass flow sensor will give an intake backfire during acceleration on drive. also the hesitation can be felt.

better start from basics such as fuel injectors.

 

I'd certainly follow Sleepwalkers advice, but I'd start by getting my money back from the garage for the last unecessary replacement (through their mis-diagnosis)! If necessary, tell them to put the old one back - it was obviously ok...

Good luck
Geoff

 

They installed a new air mass meter and it didn't change. The rough idle is still there. Also could not find any vacuum leakes and the motor mounts are good. He said the next step would be to clean the throttle body but it doesn't look that dirty and take the exhaust manifold off to take a look inside. Any other options???

 

The whole fueling system is probably dirty and just needs to be cleaned. After 11 years is a good time to hose it out.

 

Well I finally got the car back after two weeks, He called and said that it was fixed and I can pick it up. I asked him what it was and he said that he cleaned out the throttle body and removed the manifold because someone used silicone on the gaskets and some got inside the ports. He had to suck it all out and then the car was fine. I went to the garage and took it for a test ride and it ran fine, then I paid the bill $798.00!!!!When I got home and pulled into the driveway, guess what? Rough idle is back! The next day(Thanksgiving morning)
I poured some fuel injector cleaner in the tank and drove it to work. When I pulled into my parking spot turned off the car and removed the key, the car kept running, yes kept running without the key in. The only thing I can think of to shut down the engine was to pull some plug wires to stall it out. When I removed the plastic air tube that runs across the spark plug cover the engine shut off. I thought ok, I put the part back on and tried to start the car but it would not start, just turns over like it wanted to start and the dash lights were on as if the ignition was turned on even without the key in. I disconnected the battery for a minute, I guess the computer then reset and everything was back to normal. Did anyone ever experience this kind of nightmare???