300sel idle

[Wesley628]

I have searched and got some ideas, need advice though. My 88 300sel will not run at idle, if you hold the idle up with foot it misses a little, but runs. Driving it is fine. Runs, goes up to speeds, shifts great.

The problem started with a no start, after a shot of starting fluid, had a back fire through the air intake, it started, but would not idle. It ran fine down the road, it just will not idle at all. I got it home, checked for vacuum leaks, checked plugs, wires, and cap and all good. It is running rich it seems, black soot smoke coming out of exhaust. No check engine light on either. I just did ball joints, shocks, brakes and rotors, trans filter and trans yoke...maybe after 190k and not having to really replace much she is in shock! lol. I am leaning towards and idle air control, might take it off and clean it tonight...any suggestions? This is actually my daily driver so it would be greatly appreciated!

[pawoSD]

I too would check the idle air valve.....check the condition of the spark plugs.....and the CIS temp sensor at the back of the engine too.

[alabbasi]

Ever figure this out?

[Mike Murrell]

May not be the number one suspect, but I keep thinking "ignition coil" - black sooty smoke going out tail pipe...........

Primary side could be weak; secondary OK.

[alabbasi]

I'm thinking the same thing for my issue. Bad coil manifests once it warms up.