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C6 Corvette ZR1 & Z06General info about GM’s Corvette Supercar, LS9 Corvette Technical Info, Performance Upgrades, Suspension Setup for Street or Track
Well I am stumped. When I rebuilt the torque tube and had the exhaust off I noticed some of the runners in the collector were either real sooty or completely clean. This was on both sides of the engine and seemed the front 4 cyls were cleaner than the rear 4. So that sparked (heh) my interest to take some plugs out.
Some are black and sooty to the point I worry about them failing, others have a nice black ring on the base and clean insulator, then others are completely squeaky clean!
Pic is of cyl 2 soot cyl 3 squeaky clean.
4 & 6 had black base white ceramic, 8 was squeaky clean (just to compare banks so we know its not a bank issue). Seemed to get cleaner as it went from 2 to 8.
Wtf is going on? Thoughts? I developed quite a surge low rpm (1600) on highway with barely any throttle that was never there before. Could be related...
Vac leak? Fuel delivery issue? Injectors?
Thanks all!
Black Spotless
Last edited by Apocolipse; 10-23-2018 at 08:03 PM.
No problem there at all - I have swapped around injectors to see if it helps.
While I had the rail and injectors out I added some Redline SI1 to them in hopes maybe the spray was clogged a bit? Looked squeaky clean which makes me worried...
This seems to have been an issue since installing the MSD so I am holding it accountable. Could be an air delivery imbalance or vac leak 🤔
These were taken after HPDE and highway cruise back home on the old TR6 plugs (have since swapped to TR7 in hopes of getting rid of some KR). So this has been happening for some time now but becoming more apparent as highway cruise light throttle misfire.
About 7-8000 km probably. Leaked pretty bad at first but tightened it up after some heat cycles and seemed to calm down.
Did you check it again periodically?
I ask because I'm curious as to how often I should check mine.
Was it loose before you removes it to move injectors around?
I checked it after about 2k km and remained tight. I increased the torque values on the bolts which made the manifold collapse right down onto the heads and seal like the OEM does instead of relying on the gasket to maintain torque. This is the issue many people have as the gasket compresses over time and loses tension causing a vac leak.
Checked for vac leaks on the manifold, lines, gaskets, maf, etc...nothing.
Curious though - I was running open loop tune and had my idle really lean causing that nice cam lope we all love (k501). Wideband read 17:1 + and bounced around quite a bit.
I added fuel and brought it down to stoic which smoothed it all out a lot and got rid of the agressive lope...hypothesys...lean misfires at idle causing cylinders to load up based on slight airflow characteristics / differences which led to the uneven burn look on the plugs?
If you look down the sooty ones the black eventually disappears (reading plugs midrange and wot).
Thoughts? It is winter now so shes in storage...this is going to be a long one.
10-23-2018, 04:48 PM
Injector issues??
