97 C230 running rough and using gas
 

This is a former Starmark car with 102k that has had a lot of work due to me whining about every last thing at the dealer. Past 4 tanks or so, various stations, all 93 octane, motor buzzes and vibrates, and my mileage is notably down.

Winter fuel?

I use techron every 5k, the car has had the entire plug/wire/resistor setup replaced 15-20k ago, oil is clean, motor mounts just passed indie inspection.

I am not familiar with your car but I think that until you get the codes pulled by your indie or the dealer the good folks on this forum won't be able to help much.
Good Luck, Dan

Yeah, I don't think there are any codes though. Codes were pulled 3k ago for general diags and nothing was found.

Could something in the emissions system cause this, like MAF, EGR, etc? It's subsystem that, to my knowledge, has never had any repairs.

your using too much Techron, that much detergent will mess up your fuel pump quicker.

Really??!

I use the small bottle, 12oz I think, nefore each oil change. Too much still? What does it do to the pump? How often shoudl I use it?

Would that make the car run rough and eat gas though?

I'll go back and read the whole Mercedes tech article and report back later. But it does state "...corrosive additives that clean injectors.." as a "troublesome debris". And the effect of additives (Techron) "What is it doing to the rest of the system?" could also be an issue.

You shouldn't need Techron, just purchase proper octane gas from a quality manufacturer, and a station that is busy selling lots of gas.

Change fuel filter as the Service Manual states.

Also when motor on your car vibrates what is your tach doing at that moment?

Ouch. Not good! I've probably used it 5 times or so since I bought the car at 60k, every 5k miles for the last 3 oil changes.

I've always been told Techron was the nectar of the gods. I knew a BMW tech who used it as regular maintenence.

Could you describe the buzzing and vibrating? When does it occur exactly? Where does the noise seem to come from?

Mike

Hey Mike,

It's just a general roughness in the motor. It's not a driveline shimmy or a tire issue, I know that much. It's as if the motor is just transmitting enough vibration to feel it through the floorboard at times. I just drove it tonight and it was smooth, but last night it was rough. Seems like it isn't a gas quality issue, but I'm at a loss. I'm just used to the car being really smooth all the time.