old blue...if you're refering to george, he sold his shop a few years ago, but i'm right down the street at mercedes centrum( 425/ 454-2680) i had a 420 in a while back that had been every where and everthing done to try and correct his rough idle. so it was easy when i got it. the last thing to check is the idle position switch. this will cause a rough idle when the ignition is ok and the fuel delivery is ok...paul

Hi Paul and everybody :-

Now my rough idle is not that bad since I put back 8 NGK copper core spark plugs. Will install back Bosch copper plugs later though.

Is that big throttle position switch next to the idle speed valve (or called slider valve) ??? If not, can you tell me where is that located ??? Can I install that myself if possible ??

Thanks in advance.

Some Good info Bump
 

Interesting
My ignition wires look old
slight rough idle
more like hi idle
drive idle is normal 650

Don't know what spark plugs are or look like
that would be a good thing to look at...

rough idle seems to be more ignition that fuel?
wonder about high idle
hoping vac hoses as I plan to replace old dried ones

are you saying that the 8 fuel injectors were replaced at the cost of $670.00 parts and labor. i was quoted $11oo for parts and labour giving a break because each one would cost $200.00 making the real total $1600, i guess it depends where you live, in the expensive area of san francisco where i live. opposed to your portland area. great info here on this message board, i joined tonight be kind i am new, i own a 420 SEL 1989 173 miles love it had a 1988 420 SEL 250 miles, yes i am female, blonde, with dark roots, so i have a pulse.

That was a 2002 price quote. Each post is dated in the upper left corner.

Welcome,

Dan