#1 plug dry carbon fouling, rest A-OK, what does it mean?

[Red Dragon]

hey everyone,

as the title indicates I have some dry carbon fouling of the number one spark plug, and the rest look as they should. Any ideas on this one?

No I have not checked valve clearances, could this be the problem. If so could someone explain why?

Thanks!

 

[Nick M]

If just one cylinder is fouled, it means that cylinder has issues.

 

[7MGTEsup]

If just one cylinder is fouled, it means that cylinder has issues.

I think he was awear of that, possibly a faulty plug?? try changing out the plug. Check all your connections to the plug and coil, check the clip on the injector is pushed in tight. Possibly the injector is going south???

 

[Red Dragon]

I think he was awear of that, possibly a faulty plug?? try changing out the plug. Check all your connections to the plug and coil, check the clip on the injector is pushed in tight. Possibly the injector is going south???

This is with a new plug (NGK iridium, less than 50 miles on it), and it was the same as the old plug I pulled out (NGK plat, 20k miles on it). New plugs, new plug wires, everything tight. injector is RC 550, its getting up there in years, but not that old, like 5-6 years old.

This indicates a rich condition in the cylinder does it not? I went a step colder on this plug since I run 1.1 bar peak, but the other are still ok, just this #1 carbon fouling. I don't burn any oil except at start up when the car has been sitting for a day or two and then just a brief puff at start up. But this has happened on all three supras I've owned, so wasn't a cause for alarm.

any other ideas? If no ideas, how about a good mechanic in HOUSTON who understands these cars. I have talked with three shop managers at dealerships and none of them have any techs with any experience on the 7mgte.

 

[7MGTEsup]

I don't burn any oil except at start up when the car has been sitting for a day or two and then just a brief puff at start up. But this has happened on all three supras I've owned, so wasn't a cause for alarm.

This would indicate you have a bad valve stem seal on the number 1 cylinder.

 

[Red Dragon]

anyone have any diagnosis ideas to figure out exactly whats going on. The less invasive the better, of course.

 

[mrnickleye]

The #1 cylinder injector appears to be runing a bit rich. Try running some fuel injector cleaner thru the gas tank for a couple of tanks.

A company called BG makes a really strong one called MI3000. We sell it at the shop for $10. They have a website. Lots of pro racers use their stuff.

 

[IJ.]

Swap #1 and #2 injectors around and see if the issue follows it.

 

[tlo86]

blow off valve?

 

[dbsupra90]

Swap #1 and #2 injectors around and see if the issue follows it.

i agree. if not the next look is valve seal then piston rings.

 

[Red Dragon]

i agree. if not the next look is valve seal then piston rings.

swapping the injectors sounds like a great idea, I think I will try that. But gonna need to grab some copper autolites for this test.... no more iridiums until this is figured out.

Thanks guys

86temp, what do you mean by bov? I run 1.1 bar and use the BOV off the MKIV, probably have some surge, need to get another one. You think this could affect one cylinder?

 

[mrnickleye]

Perhaps the #1 injector is leaking, (not closing all the way), and causing a rich condition.

Is it a little hard starting (like 3-5 crankes) when its warmed up but been shut down for several minutes?? (No cold start injector operation)

The fuel pump would have to pressurize the system if the injector leaks, thus causing the hard/slower start.