Originally Posted by waynesb

This sounds similar to my issue. I'm a newbie having bought a '94 SL280 with the M104 engine last Sunday, (my first Merc), and walked headlong into a badly running car. I can't complain too much as I didn't pay too much for it, (NZ$12,500 about US$9k, it's pretty untidy) but it would have been nice to see it coming...

So after reading multiple threads during the week about badly running M104 engined cars decided I'd better take Arthur Dalton's advice and replace the suppressor between the coils and the spark plugs, and the plugs themselves, (I know, only F8DC4 plugs. I gapped them at 1mm. They were selling cheap because they're a deleted item so I bought 12! ;-). While doing that I noticed all the HT leads to the other plugs had white points where it looked like they were shorting so I bought a set of those too.

Anyway having replaced leads, suppressors and plugs, the car is running better but it still "coughs".

I can now get it to happen regularly. If I slow down to about 40km/h and then gently depress the accelerator, it'll hesitate and cough and then slowly pick up. If I bury my boot it'll only stumble a little, (hardly noticeable), and then GO like a cut cat! The cough sounds like it might be fuel going off in the exhaust but it's not REALLY loud, just quite noticeable.

Is there anything else I should try before replacing the MAS?

I haven't priced one yet from my friendly discount Mercedes parts guy, but I can feel the pain in my wallet all ready! Still if I'd seen all this coming I might have lost my metal and not bought the car and it's such a cool car! ;-)