C200 (w202) misfire

[gbalfour]

Hi folks,

First post - but been lurking for a while now.
Running a c200 auto 1998 (61k miles on clock! - not high mileage!)
Problem I am having is misfire and rough running occasionally on idle.

Idle problem feels like I am dropping on to 3 cyls for a few seconds then sorts itself out.

Misfire occurs as hesitation followed by popping thru ehxaust when going back on power after lifting off (example would be exiting a corner after braking coming into corner).

Obvious thing from reading on here is MAS - but I changed that out yesterday with no effect.

I had a similar problem a year ago - sorted out by a service last year - but service / MAS change yesterday has not fixed it this time!

Only thing different was last year's service changed spark plugs.
So I am thinking either plugs or possibly leads (perhaps last year's service just improved contact on a dodgy lead by pulling replacing plug leads???
Another pointer to ignition prob is increased radio interference (clicking thru speakers intime with engine revs).

Wot do you think?? Plug leads? Plugs should not be on way out after 10K miles or so?


GB

 

[gbalfour]

C200

Anybody out there seeing this post?

Posts either side have loads of views / replies - mine does not.



GB

 

[Myros]

plugs and leads

are going to be the only things which interfere with your radio, so your detective work is looking good. Have a fiddle with the conections and see if that helps. The backfiring you are experiencing is unburnt fuel igniting in the exhaust on its way out, so again, an ignition or timing fault is indicated.
You''ll probably need a new set of coil packs, as the wiring is biodegradable apparently.
Mine fried after a spark plug failed and raised the temperature in the recess in the cyl head where they live.
The plugs could well be goosed after 10 k. I never let mine alone for that long, except in the v8, where they only work a quarter as hard as four cylinder set.

 

[jberks]

Aye - Misfire plus symptoms of electrical sparking- should be on the HT side of the ignition system.
I suspect the loom will be ok as the voltages are too low to be an issue here, but certainly a dodgy lead could give you the kind of issues you list. Check they are firmly connected and everything is as it should be and if in doubt, a new set of leads can work wonders. Assuming they are not 60k plugs, I'd swap them out too, just to be safe. If that doesn't work, then your on to coil packs.

 

[C220GJS]

Agree it is likely to be a high tension leak that is your problem. Take the plug cover off the top of the cambox, run the engine in the dark and you should be able to see any shorts, pinpointing your problem.
Geo.

 

[gbalfour]

C200

Thanks for the replies folks,

I'll let you know how I get on!



GB

 

[gbalfour]

Hi Folks

Turned out to be a dodgy coil pack.

All is now well again.

Thanks again for all replies

GB