Code P0301 won't go away

[grt]

have a 05 uplander with 3.5L, got a code p301 which is cyl #1 misfire. I proceeded to change the plugs, wires and now the coil pack, cleared the code, but it came back a day later. Where do i go from here? Should i replace the injector?

[Tech II]

You are getting a P0301, which relates to a misfire in cylinder one.....

Does the CE light flash at all under a load?

Can you "feel" the misfire at idle, or just revving the engine? Is there a puff sound coming out of the tail pipe? If there is, hold a tissue near the end of the tail pipe, and see if it sucks back into the pipe during a "puff".....

Can you feel the misfire while on the road accelerating, say up a hill?

If spark is ok at the end of the ignition wire using a spark tester....if compression is ok......then yes it's possible it's an injector......you can try moving the injector in the fuel rail by swapping it with another, to see if the problem moves to another cylinder.....

[grt]

It's running good, the code must be intermittent because I cleared the code and it took a couple days to come back. How big a job is it to swap injectors? Looks like I have to take the upper intake of just to get at them

[Tech II]

Yes, the fuel rail has to be removed to swap the injectors....

But since this is so intermittent, check the wire harness to the injector, to make sure there isn't a rub through condition.....you can also check the resistance of the injector, and compare it to the others....

With this being so intermittent, it could be a problem finding it......haven't seen this problem on a 3.5.....usually the misfire is cured by what you have already done......now we could be getting into "exotic" possibilities, like a broken valve spring or leaking valve stems seals or vac leak at an intake gasket......

Hopefully it's something simple, and you can report back with the fix...