Help diagnios Cylinder #4
Thread Starter
Staging Lane
Joined: Aug 2008
Posts: 65
Likes: 0
From: Huntsville, Al
Help diagnios Cylinder #4 Guys,
I am stumped, and need opinions. New Supercharged, forged LS engine with 5-6K miles on it. Runs great, with no issues. I just removed the plugs while doing some maintenance, and found all plugs to look new, except for #4, and it is Dry, Black Sooty. Here is everything I have done so far.
Installed 8 new plugs
Installed new wires
swapped the coil to other bank
swapped the injector to other bank
compression #4 test show same as other cylinders
Sprayed starter fluid for air leaks.
After all these changes and test, the plug #4 repeated.
Not sure where to look now other than pull intake to inspect, then head, then piston????? ANY SUGGESTIONS is appreciated.
I am stumped, and need opinions. New Supercharged, forged LS engine with 5-6K miles on it. Runs great, with no issues. I just removed the plugs while doing some maintenance, and found all plugs to look new, except for #4, and it is Dry, Black Sooty. Here is everything I have done so far.
Installed 8 new plugs
Installed new wires
swapped the coil to other bank
swapped the injector to other bank
compression #4 test show same as other cylinders
Sprayed starter fluid for air leaks.
After all these changes and test, the plug #4 repeated.
Not sure where to look now other than pull intake to inspect, then head, then piston????? ANY SUGGESTIONS is appreciated.
Last edited by Mastif; Oct 23, 2015 at 01:10 PM.
Place one probe of an ohm meter on the hot side of the #4 injector wiring harness and the other probe on the injector fuse teminal at the fuse box. At least you will know if it's good up to that point.
Thread Starter
Staging Lane
Joined: Aug 2008
Posts: 65
Likes: 0
From: Huntsville, Al
Thanks Thanks for the suggestions guys, I will get back on it in the morning and see what I can find.
I am posting a pic to give you a better idea of what the plug looks like, and like I said, 7 look great, and only the #4 pictured on the right is a issue.
This is dry sooty, not oil.
I am posting a pic to give you a better idea of what the plug looks like, and like I said, 7 look great, and only the #4 pictured on the right is a issue.
This is dry sooty, not oil.
TECH Resident
Joined: Sep 2013
Posts: 994
Likes: 119
From: Mechanicsburg, PA
Wow no drivability problems with a plug like that. I agree with a leak down test first. Testers are cheap if you don't have one. Compare #4 with some others as a basis. Have you had any oil consumption? The plug sure looks like fuel fouling though. You can check dwell with a multi-meter on the injector and compare with others as well. A quality spark tester would let you know if the ignition system is up to snuff. Every cause I can think of would cause a drivability concern, lol. Good luck!
Thread Starter
Staging Lane
Joined: Aug 2008
Posts: 65
Likes: 0
From: Huntsville, Al
Thanks for all the input guys, I am now in the process of doing a leak down.
Question, If the rockers are off of the the engine, can the leak down test be done with the piston in any position, or does it still have to be TDC?
Question, If the rockers are off of the the engine, can the leak down test be done with the piston in any position, or does it still have to be TDC?
Trending Topics
TECH Resident
Joined: Sep 2013
Posts: 994
Likes: 119
From: Mechanicsburg, PA
TDC should not matter with the rockers off. Leak down is done with minimal pressure, but it still may push the piston down. The results would be credible either way, barring a cylinder wall flaw low in the cylinder (very doubtful).
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
