Intermittent cold start 300SL 1991
 

Need help sorting out an intermittent problem with my 1991 300SL.

On a cold start, the engine will start but the mixture appears to be too lean. The engine idles perfectly but will stumble unless I start out in first gear. This condition will remain until the engine is up to normal temp and will improve as the engine warms up. this happens 2 out of ten times. If the intial cold start is good then I have not trouble. I have never had the problem when the engine is at operating temp.

New injectors and fuel filter did not help.

Any suggestions?

Dan

I own a 1991 300SL also. I have 95K miles. Here's my experience. It all depends on how cold it is when I do the cold start. On my car, if it's below 45 degrees when cold started, it runs just fine. But if it's say 50 degrees or above, it will run lean, lack low end power, and stumble a bit. After about a minute of warming up, it runs OK. So, it's outside air temperature sensitive. Of course, the warmer the outside air temperature, the more quickly it comes up to operating temperature. There's an awful lot of complex stuff happening while an engine warms up. Since I hate to leave my car at the dealer so they can start it "cold" once every 8 hours, I just tolerate the warm up period. My condition doesn't sound as severe as yours. I'll be watching this thread to see what others have to report. Tod

You are correct about the a lot going on until the engine gets to normal temp.

I have found that the dealer here does not do well with cold starting injection problems so I will sort out this puzzle a piece at a time. I had a 1964 230SL and managed to figure out how that injection system worked.

I have subsribed to the Alldata.com/diy service support for this car and there is a lot of good information on service documents, repairs, and diagnostics.

With the excellent help of Bob Terry on this foum and the Alldata information I was able to get my hard top operational with a simple 10 minute procedure. Prior to help from Bib I had paid the dealer $175.00 to mess around with it.

I am confident that we will get this problem solved as well.

Please stay tuned.

Dan