Originally Posted by Wyatt Wackerlin

First off to the guy who first posted this when you tighten down your bolts to your intake manifold and and a few days later the code came back well when your valve cover blows out oil you dont tighten the bolts more thinking the gasket will hold up you "replace" the "GASKET" to "Fix" the problem because once a gasket starts to leak or has been exsposed its been compromised meaning its junk and time for a new one .If your engine light is on solid its not to bad but if its blinking then you have bigger problems and what I mean is if its solid theres a 2 second difference in the timing and if its flashing theres a 10 second difference in the timing. And dont listen to "TAINTER" when he said " YOU HAVE TO USE ACDELCO OR IT WONT WORK" because I dont use nothing but "BOSCH" in my hummer h3 and ACDELCO is JUNK to me and ive been a mechanic for over 13 years and now my story I had this code come up and looked into it and the first step I did was flip flopped all the coils and still the engine light was on replacd spark plugs still the light was on then I replaced the throttle body still the light was on then the mass air flow sensor still the light was on and then I checked the INTAKE MANIFOLD bolts to see if any where loose and sure as hell there was one loose and I took off the manifold and put a new FELPRO GASKET in and my engine light went bye bye

Originally Posted by TAINTER

The only way to know if it is the valves is to do a pressure leak down test.

-If the manifold bolts are not tight (again) that will also cause the same codes again.
-Clean the TB (front and back).
-ACDelco plugs only. The I5 is a very picky motor when it comes to plugs.
-swap the coil from cylinder #4 to #1 and vice-versa. Clear the old codes and see if the code changes cylinders. If it does then you know that you have a bad coil still.

Let us know if any of this helped.

Originally Posted by Wyatt Wackerlin

First off to the guy who first posted this when you tighten down your bolts to your intake manifold and and a few days later the code came back well when your valve cover blows out oil you dont tighten the bolts more thinking the gasket will hold up you "replace" the "GASKET" to "Fix" the problem because once a gasket starts to leak or has been exsposed its been compromised meaning its junk and time for a new one .If your engine light is on solid its not to bad but if its blinking then you have bigger problems and what I mean is if its solid theres a 2 second difference in the timing and if its flashing theres a 10 second difference in the timing. And dont listen to "TAINTER" when he said " YOU HAVE TO USE ACDELCO OR IT WONT WORK" because I dont use nothing but "BOSCH" in my hummer h3 and ACDELCO is JUNK to me and ive been a mechanic for over 13 years and now my story I had this code come up and looked into it and the first step I did was flip flopped all the coils and still the engine light was on replacd spark plugs still the light was on then I replaced the throttle body still the light was on then the mass air flow sensor still the light was on and then I checked the INTAKE MANIFOLD bolts to see if any where loose and sure as hell there was one loose and I took off the manifold and put a new FELPRO GASKET in and my engine light went bye bye