Purchased this car awhile back, and have had no time to mess with it until this week when I was forced to drive it. The car's idle is smooth as glass, but when you go to take off from a stop light it will stumble. If you a very gentle and let the car get up to speed, it's fine, or if you run it up to wide open throttle it's fine, but not normal acceleration from a light. I am going to be changing the fuel filter, and plugs tomorrow. It sat for almost a year before I bought it. It just seems to starve for fuel in that mid range, if it was a VW I would say it was overfueling while at idle, but it's not. I checked for vacuum leaks, and for fuel leaks already.

Replacing the oxygen sensor in our 1991 300CE resolved that same problem.

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Fred Hoelzle

Thanks! Did it turn right out, or did it have to be heated?

My '91 used to do that, the dealer replaced lots of parts under warranty, finally fixed it with one bottle of RedLine fuel additive.

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Gone to the dark side

- Jeff

The oxygen sensor on our 1991 300CE unscrewed easily using an oxygen sensor crow's foot wrench. Unsnap/remove the passenger side front floor mat panel so you can unplug the oxygen sensor connector, remove the floor grommet, route the wire through the floor and unscrew the oxygen sensor. Installation is the reverse order. The threads of the new oxygen sensor should have Never Seez on them to facilitate future removal.

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Fred Hoelzle

Thanks again.

I am having the exact same problem with my car, did the o2 sensor work for you as well? Thanks!

Sounds like fuel gone stale in the fuel system due to inactivity. In particular the injection nozzles. I'm probably the guy that threw parts at Jeff's '91 trying to cure a bad fuel problem. (Sorry Jeff). May I suggest a bottle or 2 of "Techron" by Chevron. If it improves the running characteristics at part throttle you identified the problem as clogging nozzles.

I tried Chevron Techron on the '91, didn't change it. The RedLine did.
http://www.germanautoparts.com/Chemicals/Fuel%20additives/Redline

My car never had a bad fuel problem, it just was something that started to develop and get worse when it was about 3years old, over several thousand miles. It didn't have a chance to get stale fuel, was 5years old and 120,000 or 130,000miles when I sold her (click on avatar, 1996 photo).

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Gone to the dark side

- Jeff

I had the same problem turned out to be a bad EHA valve (fuel regulator). Also had the infamous warm start problems of stalling on the first try. Once in a while it would surge at idle too. I got a used one from ebay for $25 and fixed it right up.

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97' SL600 Sport Pano - Silver
90' 300e 2.6 - Silver Donated to a family member
95' C280 - Artic White
88' 924s - Guards Red Sold
98' Durango SLT - Silver
93' 740i Tripple Black Sold
95' 900s Conv - Red
96' XJ6 - Black - For Sale
95' 325i Convertible - Montreal Blue My Project Car

This sounds like another "Ethanol Related Incident". Mechanics are seeing more and more ERI's. Spoke with eight yesterday here in the St Petersburg Florida area, all are telling the same stories. They are rebuilding carbs, replacing pumps and working overtime.

Good Luck,

I had a similar prob. with my 88 300SEL. I was able to adjust the mixture screw in the flowmeter (trial and error) which eliminated this prob. I know you should have it done at a shop using an exhaust gas analyzer. However, when I had this done to spec. the hesitation was still there.

In the past the oxygen sensor was bnad even though the light did not go on. Replacing it solved the problem which happened several times.

My 91 CE stalls on the first crank but has no other problems with idle or exceleration. I was told that the fuel regulator was the problem but never fixed it. Is the fuel regulator under the car near the tank? I've been thinking about fixing it myself.

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1991 300CE Sportline
1983 300SD TurboDiesel (Gone but not forgotten)