89 190E 2.6 plug fouling

Does anyone know if there is a common cause for plug fouling in this engine? The offending cylinder is #4 and the plug looks to be fouled by a carbon residue. It is not oil soaked, but maybe the valve seals are weak. I can take the plug out and clean it which cures the problem for about 10 minutes worth of idling. I would appreciate the advice.

Will

Reply to
Will
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It's the very well known camshaft problem.

I did one repair myself once about 15 years ago.

Reg: Harri

Reply to
Harri Markkula

I don't know of a common cause but these are the possibilities (in order of likelihood and, luckily, increasing cost):

  1. Bad ignition wire which can be checked with an ohm meter.
  2. Dirty fuel injector that's now throwing a stream instead of a spray; this would cause #4's over fueling, especially at idle.
  3. A leaking valve stem seal, but I'd discount that because only one cylinder is involved.
  4. A burned valve that's causing low compression; a compression test will confirm, or deny, this possibility.

I believe you'll find #1 or #2 are the cause of your motor's problem.

Reply to
T.G. Lambach

Do a compression test.

Reply to
Richard Sexton

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