Little

About 2 weeks ago, i go to Exxon, "$15 Super please" hand the guy my atm card. My gf sits in the car while i go inside to get a drink. I come out and get in the car. Start thinking to myself damn that thing is still pumpin, look over, 17 Gallons of Regular..... WTF!

After one killing that tank of gas, the car is idling super super rough at idle. The car is an '01 E430 with 66,000 miles on it. I dunno if its coincidence or not. I mean the bad gas shouldn't have done anything as the car shoulda just pulled timing out. I had the mass air replaced at 50,000 miles. Maybe a tune-up is in order??

Nellie B

Would've thought you'd be OK with just one tank full of 87 gas. The lower octane rating would cause more problems at higher revs (i.e. pinging) than at idle.

Maybe it's a bad tank of gas? I'd be tempted to drain the tank (responsibly of course ...) and refill from a known good source. I had a modified Lancer Evolution and that manic machine (truly cocaine on wheels) was very sensitive to octane and gas quality. Following a tuners recommendation I try and stick with 76 stations.

Hope this helps a little and good luck!

- Nellie

SDR

WTF indeed! Where do you get 17 gallons of fuel for $15?

Musikmann

I think you said you have run the car long enough to use that partial tank of 87 gas, and now that you have mostly 91+ in it, it is still running rough (?) If you are still driving with a lower-than-91 octane gasoline, I'd drive it slowly until you are at about 1/4 tank, then add 93 if you can find it. There is also something called Octane Boost I've seen in various automotive sections - I know nothing about that stuff, but I don't think one application could do any harm.

If you are now running 91+ octane and you still have a rough idle, you are close to the recommended "B" service at 66k anyway, and that certainly can't hurt anything. Your FSS timer will give you the mileage when you are due for that, but I think that is meaningless here. The multitude of sensors are supposed to tell you if you need sevice for a lot of other reasons: therefore, maybe the appropriate sensor is bad.

Lastly, I agree with Nellie B in that the bad performance (if due to low octane fuel) would be noticeably worse at higher RPMs than at idle.

Good Luck!

ml3204me

I had the same kinda results on my e320 but not from bad gas.

I really doubt the bad gas would cause the engine to continue to run bad.

After checking for vacuum leaks and bad spark plugs I narrowed the problem down to a faulty coil pack.

To find the faulty coil pack I ran the engine for a few minutes then removed each spark plug one at a time looking for a plug that was fowled or in my case damp with fuel.

Replaced the bad coil pack she idles like a dream once more.

good luck.

telemakhos

The 87 octane wouldn't cause any serious problems. The engine computer knows how to handle it. You should ease up on the throttle until you burn through the 87 and put the proper octance gas back in. Rough idle = trip to the mechanic.

MB Fanatic

Trust me filling up 87 octane will make the car run rough. My wife once filled up the E350 with regular gasoline and it sounded like a diesel truck (exaggerating), but it was bloody loud and it ran roughly.

I would suggest running some Chevron Fuel System cleaner (20 gallon one) and some premium gasoline and see if that helps.

Dan Wang

87 octane will have no long term ill effects on the car. Fill it up w the highest octane you can get your hand on to balance out the octane rating. Use can use some gas treatments such as Chevron Techron, but for the most part just using the higher octane gas will solve the problem.

Little

Nah i don't think its a gas problem anymore. I have gone through at least 2 1/2 tanks already with the usual super i always use and the rough idle seems to be gettin worse. Now i just came to realize, could this be a harmonic balancer problem?? I never thought of it because i thought only the V-6 motor was having that problem.

Musikmann

I don't know if this is a symptom of a HB problem, but I DO know that I had a '98 E430 and the service history indicated that it had had the HB replaced as a mfg recall before I bought it.