Trouble with fouled plugs

[andreic]

Hello,

I have a problem with 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.

[Dave at Pelican Parts]

Plugs fouled and burning a lot of gas means that you're running very very rich. (Check the oil as well; if it smells like gasoline change it! Gas does not lubricate your bearings very well...)

As for causes of rich running, those can be a bunch of things. Check for unplugged wires, for example; an unplugged CHT sensor wire will make for a very rich mixture. Also make sure the flap in the air flow meter moves smoothly; a sticking flap can cause a lot of mixture problems. Double-check (actually measure!!) your fuel pressure; it is possible to hook up the pressure regulator so that you have way too much pressure, causing a rich mixture.

Those are the first things that pop into my head.

--DD