Tracking down a mystery misfire
#31
That is it. No need for a gasket because there is a drain notch at the bottom. I suppose if desired some gray silicon could be used (makes removal a bugger later), but no sealant has worked well. Maybe depends how deep you want to wade? I think the top is not sealed anyway.
Second thought: Looks like that part number indicates a rubber seal across the top of the cover plate. Maybe reuse the old one, if it is there.
Second thought: Looks like that part number indicates a rubber seal across the top of the cover plate. Maybe reuse the old one, if it is there.
Last edited by JohnZo; 12-29-2023 at 07:14 AM. Reason: 2nd thought
#33
So I pulled the plate off and cycled the engine a couple times using TDC gap as a reference point. All of the teeth are there and look straight. CKP tip doesnt look bent and it doesnt look like anything has been contacting. Cleaned a bunch of sand out of the inside of the cover along with discovering a missing bolt for it. With the exhaust chugging and constant issues on cyl 5 could it be a sticking exhaust valve due to carbon? Has anyone had luck cleaning the carbon off valves from the top end? Trying to avoid a whole headgasket job if possible. https://www.robisonservice.com/servi...n_fouling1.pdf
Last edited by czerta; 12-29-2023 at 12:14 PM.
#34
Maybe put a wrench on the crank to turn slowly and inspect each pair of teeth. Perhaps a slight out of alignment could make a difference. I think a drill bit can be used as a gauge for the gap.
Hard to tell from a photo, but the 2nd and third from right look different.
Hard to tell from a photo, but the 2nd and third from right look different.
Last edited by JohnZo; 12-29-2023 at 12:09 PM. Reason: Photo finish
#35
But until that arrives anything further worth checking on?
#36
Still a bit of a mystery about over-fueling (high negative LTFT). But equal on both banks and not pegged at maximum, so not a huge concern. Might be related to choice of MAF? Another slightly possible cause is leaky injectors (checked by fuel pressure maintained after pump turns off for an hour maybe), but would be unusual for both banks to be equal, I think. The fuel pressure regulator can be checked with an air pressure gauge off the vehicle and a hand held vacuum pump, if that is still a question mark.
Do you have enough miles on the plugs to check coloration? Especially #5? Looking for oil fouling, or soot vs good color, but requires drive time. Keep watching O2 voltages during cold starts and drive cycles to get a sense of normal conditions. Keep track of gas milage to verify normal (9 mpg is not good, should be closer to 15 or 16, sometimes 13 depending on lead footedness).
Do you have enough miles on the plugs to check coloration? Especially #5? Looking for oil fouling, or soot vs good color, but requires drive time. Keep watching O2 voltages during cold starts and drive cycles to get a sense of normal conditions. Keep track of gas milage to verify normal (9 mpg is not good, should be closer to 15 or 16, sometimes 13 depending on lead footedness).
#37
Still a bit of a mystery about over-fueling (high negative LTFT). But equal on both banks and not pegged at maximum, so not a huge concern. Might be related to choice of MAF? Another slightly possible cause is leaky injectors (checked by fuel pressure maintained after pump turns off for an hour maybe), but would be unusual for both banks to be equal, I think. The fuel pressure regulator can be checked with an air pressure gauge off the vehicle and a hand held vacuum pump, if that is still a question mark.
Do you have enough miles on the plugs to check coloration? Especially #5? Looking for oil fouling, or soot vs good color, but requires drive time. Keep watching O2 voltages during cold starts and drive cycles to get a sense of normal conditions. Keep track of gas milage to verify normal (9 mpg is not good, should be closer to 15 or 16, sometimes 13 depending on lead footedness).
Do you have enough miles on the plugs to check coloration? Especially #5? Looking for oil fouling, or soot vs good color, but requires drive time. Keep watching O2 voltages during cold starts and drive cycles to get a sense of normal conditions. Keep track of gas milage to verify normal (9 mpg is not good, should be closer to 15 or 16, sometimes 13 depending on lead footedness).
In terms of plugs they were swapped end of nov for a total of probably 250mi-300mi on them. 5 looks oily/dark and wet. Rest look fair but not cooked. Excuse the poorly done photo
#38
Black and oily is a problem that could be caused several possibilities. Maybe in-leakage at the valve stem seal(s) letting oil into the cylinder (not too hard to diag and fix, unless the valve stem is scored), or even an intake valve that is not seating properly (compression check). Or could be injector malfunction. Or problem with lack of spark (plug, wire, insulators, coil, ecu). Or could be piston ring problem (compression check). Maybe start with compression check. Don't reuse the oily plug.
#39
Black and oily is a problem that could be caused several possibilities. Maybe in-leakage at the valve stem seal(s) letting oil into the cylinder (not too hard to diag and fix, unless the valve stem is scored), or even an intake valve that is not seating properly (compression check). Or could be injector malfunction. Or problem with lack of spark (plug, wire, insulators, coil, ecu). Or could be piston ring problem (compression check). Maybe start with compression check. Don't reuse the oily plug.