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.

[andreic]

More tests, more confusion. At the suggestion of a local Porsche mechanic, I tried the following test: start it, run it at a certain RPM, create a major vacuum leak so as to lean the mixture (if it is too rich). The goal was to see if I get an increase in RPM's -- as this would indeed indicate that the mixture is too rich. Or if it would try to stall, it would indicate that the mixture is normal or too lean.

Lo and behold, I did just that. With the engine running at 2000 RPM (my son holding the gas pedal steady) I removed the oil filler cap. My hope had been that the subsequent leaning of the mixture will make it run smoother and at higher RPM. No joy. In fact nothing changed at all, not the RPM, not the rough running!

But one strange thing I noticed: putting my hand over the oil filler neck (with cap removed) I could feel quite strongly the engine pushing air pressure out through the neck. Is this normal? It felt strange to me, but maybe it's ok.

And the smoke from the exhaust is terrible -- in less than a minute I managed to make a cloud of smoke that hung around the street for 10 minutes or more, smelling very bad (I am almost certain it is burnt oil). At some point I thought that someone played a prank on me and poured a quart of oil in my gasoline while the car was outside, but then I remembered that it is hard to even find the fuel tank if you don't know where to look for it... I am sure large amounts of oil get in the cylinder(s).

One last thought: if it is only one cylinder that is affected, maybe I could isolate it either by looking at the spark plugs (I already did that several times, but maybe after I've run the engine a bit more?), and/or maybe by pulling out one spark plug lead at a time, and seeing if the smoke diminishes (as then the offending cylinder would not fire anymore?). Is this a possible plan of attack? Is there anything inside the engine that could have failed and push oil into *all* cylinders? Like overly high oil pressure?

Final question: do you guys think inspecting the lifters and valves could reveal something useful? Could something wrong with the valve train be getting oil in the cylinders and making the engine run very rough?

Sorry for the many questions, but I really really don't know where to go from here.