Badly fouled spark plugs Options

[andreic]

Hello,

I have a problem on my newly rebuilt 1.8L engine, with L-Jet.

Yesterday as I was driving home the car simply quit about 5 blocks away from home. Until this point it was running very well. I had to have it towed home and now I started trying to diagnose it.

So far I've checked that the fuel pump operates when opening the flap in the AFM, so I suspect I got fuel pressure right. The starter spins the engine well.

I have strong spark on the main distributor cap wire (coming from the coil), and putting a brand new spark plug into one of the spark plug wires I have spark at that too. (Originally I was too lazy to pull an actual plug from the engine.) But this morning I tried pulling a spark plug from the engine, and it is completely black and covered in carbon. Not wet, just covered in a thick layer of solid black material.

I can't check right now whether the spark plug from the engine is fouled badly enough to not give a spark at all, or if it still is OK. (I need to wait for my son to come back in the afternoon to help me, this is a 2-person job.) But assuming the spark plugs are the problem, can somebody offer a guess as to what could have caused the engine to foul the spark plugs so badly and so quickly as to stop the engine while driving? Before that there was no indication something was wrong.

Other slightly strange things.

a) I've noticed the car burns a lot of gas. I barely get 20 mpg in mixed city/highway driving.

b) I have about 600 miles since the rebuild, engine ran well all along.

c) The only other issue with the car is that I can not get the idle right: it seems to idle at 1800 rpm most of the time, but if the engine is well warmed up (after about 1/2 hour of driving) or if I hold off the clutch as I come to a stop until the rpm's come down to 900, it'll idle at 900. I've tried two different throttle bodies, thinking it may be the throttle that sticks, but it behaves the same way with both. I started to suspect that the distributor is sticky and does not retard the idle sometimes.

Any suggestions, highly appreciated.

Thanks,
Andrei.

[HAM Inc]

Could it be that the extra rich fuel caused the cylinder walls to glaze, and then this started afterwards letting oil into the combustion chamber? If so, do I understand correctly that I should first fix the rich condition, and then try to seat the rings by driving it at wide open throttle in too high a gear, so as to have low RPM's?

Absolutely. It happens all the time to engines of all ages and overall health.

New engines are especially vulnerable to cylinder wash down during the ring break in period.

Sometimes repeated heavy full throttle loading will bring ring seal back. Sometimes it won't.

Lugging from a standing stop through the gear box and coasting back down in high gear seems to work best. Wash, rinse, repeat.