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Discussion Starter · #1 ·
It started with my 05 TB turning on the check engine light. I checked the code, and it mentioned something about the knock sensor going off. I checked around and decided to replace the spark plugs in the truck. When that was done, I though everything was fine, except coil pack 4 and 6 didn't want to go in with the new plugs in place.

I had a neighbor who works as a mechanic take a peek and he smacked me upside the head for lightly cross threading the holes for #4 and 6. Gave me a thread chaser to clean out the threads and then finally coil pack 4 and 6 went in.

Except now the truck misfires, idles at 600 to 750 rpm. The code came out indicating that coil pack #6 was misfiring. Following some suggestions on the forum, i swapped coil pack #6 with coil pack #2 (I didn't want to mess with #1 due to the wire harness in the way). The new error code indicated that coil pack #2 was misfiring.

I'd have replace it by now except the neighbor mechanic, who I had check over my work so far, said that he could hear (I'm deaf, which is why he could hear it and I couldn't) the rocker arm clicking every time the engine misfired, as well as a sucking sound, at the exact time the engine misfires.

I'm thinking to take the valve cover off but before I go into that route, I thought I'd check on the trailvoy forums before I do anything that would be costly. (Neighbor doesn't like working while not at work, even for a bribe of a 12-pack black butte porter)

Suggestions?

Am I on the right path or should I just go get a new ignition coil and pray that's all I need?
 

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2005 chevy trailblazer_ls
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Can He locate the cylinder with the sound? It may just be because that cylinder isnt firing that it sounds strange. If the missfire moved with the coil I'd go ahead with the coil unless he's certain that there is a internal problem that needs further investigation. You can run a compression test on the questioned cylinders as well.
 

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2007 chevy trailblazer_ls
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Get a new coil before going through the trouble of ripping apart a valve cover. Be alot easier and alot less work. Also will avoid any unwanted damages/other broken "needs to be replaced" nowparts.:m2:
 

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Discussion Starter · #4 ·
Can He locate the cylinder with the sound? It may just be because that cylinder isnt firing that it sounds strange. If the missfire moved with the coil I'd go ahead with the coil unless he's certain that there is a internal problem that needs further investigation. You can run a compression test on the questioned cylinders as well.
He said it was the 2nd cylinder. The rattling and vacuum sounds were only happening when the engine misfires. Otherwise he couldn't hear it.
 

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2003 gmc envoy_slt
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Just to be sure, I have to ask this. Do you have all the coil wires in the correct order. Often, if you can hear a sucking sound and back firing the timing is off. :duh: Sorry. You said missfire, not backfire.
 

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Ok so let me understand? The problem was in cylinder #6 and has now located itself in cylinder #2 after swapping the two coils? I say do a compression test it s/b ok. Double check all your work and go get a ignition coil. Since the coil wires dictate the timing and you swapped 2/6 and the miss coded in 2 now. The wiring wasn't moved. or changed.
 

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Discussion Starter · #7 ·
Picking up a $135 core pack today at the local stealership.

It was 1 dollar more than another dealership, but considering the distance, and current gas prices, i'd pay 1 dollar more and still be ahead.
 

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Discussion Starter · #8 ·
Got the new coil pack installed, truck doesn't seem to be misfiring. However, it's idling at 600rpm and feels rough.

Should I take the throttle body out and get it cleaned?
 

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2004 gmc
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Should I take the throttle body out and get it cleaned?
Yes. Always a good idea about every 30K miles. And don't forget to follow the instructions in the Article and leave the battery disconnected for 30 minutes. It may run rough when you first put it all back together, but that's the PCM learning how to deal with the newly cleaned TB. It adapts.
 

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Discussion Starter · #10 ·
After some tweaking, spraying, growling, stomping, more spraying, and more tweaking, the truck's working better than it had when we got it used.

Thanks for the help.
 
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