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Discussion Starter · #1 ·
2005 envoy 4.2 engine skip poor performance . So I change my valve cover yesterday because it was cracked from the previous owner and that went smooth but I have an engine skip now and I’m not sure why it feels like a cylinder misfire but I checked every single one by pulling it off and noticed a substantial difference when I put it back on.
So I have eliminated the coil pack also the best of my knowledge there’s no vacuum lines that I disconnected the only hoses was the one to the valve cover and the other one that goes to the PCV on the intaketopPossible connections it looks like I connected what I disconnected which looks to be I think nine or 11 connectors. There are no real vacuum lines to take apart but that’s what it feels like as if a vacuum line was off.

The only two hoses I took off or the one from the air canister to the valve cover and the other one to the intake I guess that’s the PCV. Now I did get a check engine Of a cylinder five misfire but after I cleared it with a tool it is not come back. I’m lost for the first time in fixing hundreds of cars.
 

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Discussion Starter · #2 · (Edited)
So I have an update I sprayed carburetor spray all over the intake to check for leaks no hesitation in the idle no change.

Now the check engine light came on again this time it says engine misfire cylinder two in the beginning I got a misfire cylinder five I swapped coil packs five with two so it’s possible that the coil pack is the problem.

Here’s why I need help, why is it when I lift coil pack out the engine does hesitate a bit indicating the coil packs doing its job if that’s true what’s causing the misfire and what do I do? Should I change the coil pack anyways and see what happens?//I spayed carb cleaner lookin for an intake leak and nothing. I recheck all the connectors again. I am lost.
 

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2004 chevy trailblazer_lt
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Before you do anything else, what exactly are ALL the OBDII codes that have been set and read by an OBDII code reader? Also, are there any historical or pending codes?
 

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Discussion Starter · #5 · (Edited)
Remember after I got the error code for cylinder 5 misfire I swapped coil pack with clay 2 now I’m getting a cylinder two misfire. so I guess I change the pack. I never knew that it can fire but still skip. I also notice even if your remove it from the plug and it runs worse does not mean it's good and not the problem, The error codes say it all.
 

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I do not know what Santa or Sean Darren have to do with anything but it looks like you have a bad coil since when you moved it from the #5 cylinder to the #2 cylinder the misfire followed. Time to get a new ignition coil. You should replace it ASAP so you do not damage the catalytic convertor.
 

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Discussion Starter · #8 · (Edited)
Sorry about the typos I was driving all set fixed I went on Facebook I found a guy who had coil packs from a car in the same town as me from a scrap car. They look brand new so I picked up a pair for 25 bucks I installed it on cylinder 2 the car is running smooth. So apparently if you stare at these coil packs the wrong way they failed you. I thought for sure I forgot something but that would have been a 1st cause I count all my connections.
 

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Happy to hear you got it running right again!
 
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