W140 S500 Uneven running

[jensssscar]

Can someone tell me what is happening to my engine? It started about a month ago, I live in central London so it takes ages before I get to an open road, so I am in traffic for at least half an hour. The car starts fine and continues to run perfectly for about 5 mins or about 1.5 miles, the temp gets to about 80, them it becomes VERY lumpy probably firing on 4 or 5 cylinders. This lasts for about 10 mins, then it gets a bit smoother. After about 15 mins (still in traffic,rarely going over 20 mph) it clears itself completely. I can then drive all day, stop for a couple of hours and it starts and runs again perfectly. Next time I use it, probably a few days later it does the same thing.
Anyone know what is going on?? It is a standard S500 1995 with 56k on the clock.

 

[television]

Hi and welcome to the forum

Could this be a MAF problem just starting

 

[grober]

Definitely sounds like a mixture related problem.

 

[television]

Definitely sounds like a mixture related problem.

My thoughts were that it starts well, so electrics OK and that the MAF is not part of the starting from cold, and it has to get hot before the problem starts

 

[grober]

This site is always worth a look for W140 owners of that vintage. http://pages.prodigy.net/jforgione/MB_S500.html