I know I am new to this comunity, but i could really use some help. I recently bought a used 2007 hummer h3. After having it for a week i got a misfire on cylinder 5. I changed the coil pack and injector on that cylinder but still have a misfire. my next step is a compression test. has anybody else had a head problem like this? i have seen many threads on misfires but none as spacific. please help me with this.

 

What code are you getting when hooked up to a code reader?

 

Who exactly changed the coil pack? Are you 100% positive the connection is good? Wire and how is it seated... Dumb question but your spark plugs are in good shape?

 

I personally changed the coil pack and injector. I have checked and rechecked all the connections. I even pulled the plug and cranked it over. I got spark. The plugs are new as well. I don't know the actual code I have a friend at the local dodge dealer that ran a chec and that is what he said. The light comes on for a day or two then goes off for a few minutes of driving then comes right back. I also cleaned the throttle body since it was already off. Thanks for helping me guys. This is my first hummer and I love it, just need to work out some glitches.

 

What kind of new plugs are you using?

 

The factory AC Delco replacements.

 

when i pulled the resonator box to replace injector i noticed that the rear two bolt wur loose. i dont know if that would make a difference in the amount of air the cylinder 5 was recieving, but i tightened them all up when was complete. still have a code thrown for a cylinder 5 misfire.

 

does anyone else have any segestions?

 

Have a leak down test done, Probably the head.

 

That was gona be my next thing is compression test and a leak down test. but i have a waranty that will pay for any valve problems in the head and so on. it will not cover practically anything besides if my whole top end suddenly turned into a big pink bunny rabit and hopped away, then i would have to prove that!!! i am basically trying to eleminate any other problem besides the vavetrain in the heads or piston or ring failure. thats all they will cover.