Need help with this- 2002 envoy with 224,000 on the odometer. I have owned the truck since 2019 and have done quite a bit of work to it and now here we go again....
After replacing the plugs, intake manifold gaskets and valve cover gaskets now the thing is randomly misfiring and it really is random. I put fel-pro gaskets in and ac telco 41-103 plugs in. Now when going down the highway its almost as if you can feel one of the cylinders cut out and you could smell unburnt fuel (which somehow has went away in the past week). Since this has started I replaced the fuel filter today and went for a long test drive and still the same issue. When its running good, it runs PERFECT, but when the misfire kicks in it runs like trash. I have also replaced the vacuum hose that is on the side of the intake (had big cracks in it from when I moved the hose to get at the intake bolts. I put a new cat in it back early 2020 bc the stock unit was plugged badly and caused a crack in the exhaust manifold. Only code it throws is a p0300 and yes before anyone asks, I have cleaned the throttle body twice in the 2 years I have owned the truck and that includes when I replaced the plugs. I don't know what else there could be to do before I have to do a compression test and all that jazz but I do not believe this should be necessary seeing as the problems did not come up until the tune up was done. truck ran perfectly before the work was done, you could just tell it was time for a tune up. Anything I missed that I don't know of?
After replacing the plugs, intake manifold gaskets and valve cover gaskets now the thing is randomly misfiring and it really is random. I put fel-pro gaskets in and ac telco 41-103 plugs in. Now when going down the highway its almost as if you can feel one of the cylinders cut out and you could smell unburnt fuel (which somehow has went away in the past week). Since this has started I replaced the fuel filter today and went for a long test drive and still the same issue. When its running good, it runs PERFECT, but when the misfire kicks in it runs like trash. I have also replaced the vacuum hose that is on the side of the intake (had big cracks in it from when I moved the hose to get at the intake bolts. I put a new cat in it back early 2020 bc the stock unit was plugged badly and caused a crack in the exhaust manifold. Only code it throws is a p0300 and yes before anyone asks, I have cleaned the throttle body twice in the 2 years I have owned the truck and that includes when I replaced the plugs. I don't know what else there could be to do before I have to do a compression test and all that jazz but I do not believe this should be necessary seeing as the problems did not come up until the tune up was done. truck ran perfectly before the work was done, you could just tell it was time for a tune up. Anything I missed that I don't know of?
