I replaced seals and spark plugs on my 89-300E and I wonder if it might have affected the timing. The engine is running rough.

Thanks

Did you use good spark plugs? If the car calls for platinum, did you use platinum? Did you check the gap on each of the new plugs before installing? Did you torque them down properly? Did you reconnect all your plug wires in the right order?

I don't think there's any way that new spark plugs can affect timing, per se, but they can certainly affect combustion and engine performance. If your plugs are wrong, or are gapped incorrectly, the engine may run roughly.

But, what do I know, I prefer my spark-plug-less 240D. Only recently have I also owned a gasoline-powered automobile.

- Nathan
'83 240D, 250k miles

Check that you havn't crossed any plug wires.
Happens to the best of us !

What seals did you replace? The 103 engine should use the copper core plugs only, not the plat's. Never use the plattinum in the 103 engine. Just check the firing order (stamped in the plastic on top of the valve cover)

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Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

I replaced the valve seals on number 3 and 4 from the front.
I used bosch copper plugs. Properly gaped and properly wired.
Still I have roughness during idle and at a stop in an intersection. It feels like mis-firing. Help.

Jaime...

Has the lumpy idle problem started since the valve stem seal change or was it present before? If the problem has just started ,could you have damaged the valve head by forcing the valve against the piston during removal of the collets.Or maybe seals incorectly fitted.If the lumpy idle was there before especially when stoped in drive after a long run could the valves be excessively coked up.

The rough idle started after I replaced the seals. Im happy to say none of my plugs are getting gummed up as before.
If I caused the problem after replacing the seals, will a diagnostics test show if the seals are the root cause?

Thanks,
Jaime