Fueling tip, tighten the gas cap.

[spdickey]

One big tip, tighten the gas cap after filling. i didn't crank it around enough at the first fill, about 3 miles down the freeway the engine light came on. We're in massive bumper to bumper, crawling for over an hour. Mostly with foot on the brake and then letting it crawl. Engine started to miss, lost power, thought it would die, but didn't. Got a lot of engine rattle and rough running.

Finally got off the freeway, called the salesman on his cell (its after 6 pm) and asked what to do. First thing he said was "did you just fill up?" Said fix was easy, turn off the car, tighten the cap and restart. That will reset the light and get everything back. It worked! Light went right out, idle went smooth again and all is happy! Thanks Vinnie at bhbenz.com! My wife was with me and boy did i get an earful until we fixed things. Unhappiness is being stuck on the 405 in the rain with traffic at a standstill. Glad it never did get that bad.

But the rain activated wipers came off on on right in tune to the rain showers. Rear one too!

[SMART]

Great real life update!

[Old smart]

Yup, that is common with all modern cars; the computer thinks there is something wrong with the anti-pollution system (vapor recovery).

[jwight]

Normally all you get is the check engine light, not the rough running described above. That doesn't sound right to me.

[PassionforPassionCT]

I am a little suspect that the car would run that badly with the cap loose. In all new cars, the engine light would come on, But I dont think a loose gas cap would recalibrate equipment such as the O2 sensor and the like to run the car rough.

[SmartCard]

Originally Posted by jwight

Normally all you get is the check engine light, not the rough running described above. That doesn't sound right to me.

true....I guess we'll need more data points - any volunteers out there for loosening their gas cap??

[spdickey]

The dealer told me it was a common Mercedes thing for the engine to run rough, not just the check engine light. When I first stopped to tighten the cap, I didn't turn off the car, light still on and still ran real rough, like it would die any second. Later I turned off the car, pulled the key and restart. Everything was fine after a about a block. It must have reset something in the computer.

I've done the same thing in my '07 Prius, but it just turned on the light. I thought it was the gas cap when the smart engine light first came on, and since I was on the freeway I thought I'd just tighten it when I got home. Then the engine got real rough, it was a bad traffic night in the rain on the 405. The crawl was actually too fast, had to keep my foot on the brake most of the night.

Things smoothed down after tightening the cap and then turning the car off and on.

[jwight]

I guess Mercedes figures the light isn't enough; if you keep driving the computer disables your car.

[maxtraxduffy]

sounds like it loses manifold vacume to me.