First time poster here, im typically on the powerstroke forums, mustang forums.
Picked up a 2004 suburban with the flex fuel 5.3, slight misfire. Pued the code, p0300, multiple misfire. Watching the misfire counter on the scanner cylinder 6 is consistant, with an occasional cylinder 5 hiccup. Here is what ive done so far...
1. Changed all plugs, lots of mismatched, mis gapped plugs
2. Swapped coil packs 6 and 4, misfire stayed on 6.
3. Swapped plug wires, same story
4. Verified injector operation, with noid light
5. Compression test, checked out at about 125psi.
6. Sprayed down looking for vacuum leaks, didnt find any.
7. Disconnected pcv valve, plugged off lines while running, sprayed fum cutter into oil fill under pressure, idle fluttered slightly. Per the chevrolet bulletin, that tells me intake gasket failure. R&R intake gasket, no change.
8. Pressurized the cylinder, no leakage
9. Removed valve cover and turned engine over by hand, to verify rockers were moving appropriately, they are, verified with running engine with valve cover off...
10. Tried another known good MAF because the truck was sitting next to this one, no change
11. Hooked up vacuum gauge, verified engine is making 22 pounds at idle
Still a misfire, still on 6, only at idle, and seems as though its making it idle low, but pcm desired is 599rpm, its idling right around that.
Anything I may be overlooking? Im ready to pull my hair out on this one
Picked up a 2004 suburban with the flex fuel 5.3, slight misfire. Pued the code, p0300, multiple misfire. Watching the misfire counter on the scanner cylinder 6 is consistant, with an occasional cylinder 5 hiccup. Here is what ive done so far...
1. Changed all plugs, lots of mismatched, mis gapped plugs
2. Swapped coil packs 6 and 4, misfire stayed on 6.
3. Swapped plug wires, same story
4. Verified injector operation, with noid light
5. Compression test, checked out at about 125psi.
6. Sprayed down looking for vacuum leaks, didnt find any.
7. Disconnected pcv valve, plugged off lines while running, sprayed fum cutter into oil fill under pressure, idle fluttered slightly. Per the chevrolet bulletin, that tells me intake gasket failure. R&R intake gasket, no change.
8. Pressurized the cylinder, no leakage
9. Removed valve cover and turned engine over by hand, to verify rockers were moving appropriately, they are, verified with running engine with valve cover off...
10. Tried another known good MAF because the truck was sitting next to this one, no change
11. Hooked up vacuum gauge, verified engine is making 22 pounds at idle
Still a misfire, still on 6, only at idle, and seems as though its making it idle low, but pcm desired is 599rpm, its idling right around that.
Anything I may be overlooking? Im ready to pull my hair out on this one
