Tech changed plugs -- now it runs rough.
 

My car had a very short (1/4 second) stumble in the idle immediately at startup. Other than that the idle was very smooth.

He said I needed new plugs. Fine. He changed them.

NOW, it won't start unless I give it gas. If it does, it runs very rough and won't smooth out until I give it gas. Even then, it runs rough.

What could it be?

[He said that before long I'd need a new distributor cap, rotor, O2 sensor, and wires.] Maybe, but with the current ones it was running very smoothly, now it isn't.

Yes, I checked. All the wires are securely attached to the plugs.

This is a MB-only, certified tech.

Use Plats???

Did it run that way IMMEDIATELY when you picked it up??? Or is this something that has developed lately??

Yep I bet you he used plats. Either that or he gapped them wrong.

Also check your wires, make sure they were put back securely.

... or ressistor plugs were installed .....

No plats. Now, however, I see that they were H8DC. I looked them up and it says they are the "small style", and are listed for the following:

Spark Plug - H8DC (New Style - Small Size)
Parts # 002 159 58 03
Model: 190E 2.3-16 -- M102.983
Model: 190E 2.3 -- M102.961
Model: 190E 2.3 -- M102.985

Mine, obviously, is an M103, and it shows that I should have H9DC.

I don't know what would make 1 work and not the other. However, is this enough to cause my problems?

Also -- what are "resistors"?

It did this from day 1 after the repair.

Here is my guess: I don't think it is plug rleated UNLESS a plug wasn't check for a proper gap.

It could instead be related to a wire or connector.

I hate to admit this ...... OK here goes ..... I was going crazy trying to figure out why the 300E idled roughly every so often. When I recently changed the plugs, the loose spark plug connection on cylinder # was the obvious reason.

Check each connector. Twist them gently and tug on 'em to make sure they are on securely.

Haasman.

I'm going in tomorrow to have him check it out. He said he also "leaned it out" and maybe he went to far. I am assuming he means fuel mixture -- by what method would he have done that?

Maybe just coincidental timing and the cap and rotor should be replaced now. Your tech said they were going to need to be replaced.

Haasman

Yep, I'm actually going to do the cap, rotor, and wires.

How about this from 2phast's site: What do you think / how would one verify this?

Ditto on that.. Mide did the same thing when I leaned it out too much... By adjusting the Lambda...

Well, I seem to have a resolution.

He whips out a hex wrench, goes under the hood for about .19026 seconds (:D) and says, try that. It seems smooth as silk again.

I typically get about 20.5 MPG. With the too-lean mixture I used a full tank and got about 18.5 (which seems backwards -- ? ).

I'll update after a tank.