I have a 1993 400E and this was the first winter day. We we're visiting friends for the weekend so the car was outside. Temp was about -20C and this car did not want to start!! A cylinder fired every once in a while but at least 4 cylinders were missing. There was no exhaust noise so I am assuming that the problem is that no fuel (or not enough fuel) is being injected. I had to put the battery on charge but after MANY attempts the engine finally got warm enough that she started but idled really rough. Sounded like a whole side of injectors was plugged. Sounds like at least 6 cylinders at 2500 RPM but still having difficulty even staying idling.

Warmed the car up and drove home (180 miles). Coldest drive I can ever remember!! Temp Gauge reads about 55C (131F?) all the way, cruising at 80MPH. (Didn't warm up in traffic before we got to the highway, either). Drives ok, I think I've got all cylinders but I don't quite have full power.

Now I'm thinking that this car has been idling rough on occasions for a month or so. When I had driven it for a few blocks and stopped at a light the engine would miss when idling and shake the car enough that I would slip it into neutral to stop it. That didn't concern me because we often experience a similar problem with any car as it gets colder here. There is a point in the warmup where the engine still needs some choke but the choke has shut off. So I figured this was a similar problem - I don't any more.

Gas consumption on the way home was about what I would expect - a little heavy because the engine is running too cool (outside temp was -16C for most of the way also). So I believe I was running on all cylinders.

So I am thinking that there is a temperature sensor somewhere that is giving a false reading to the computer (hence not enough choke for cold start) but this sensor is also controlling the coolant temp and making it run too cool.

Anybody know where to look?

 

people are going to think im stuck on it but idle air control valve or HOSES should be checked for tight fit and no cracks. I had so many similar probs with that

 

That would make it run cool???

 

Check your coolant temperature sensor. Your sensor could be reading too low which would cause the gauge to read low and also supply more fuel to the engine making it run richer. That would also explain the hard starts, the sensor is giving false readings. If I had to bet, Id say that sensor is bad.