Cylinder 5 Misfire - which one?? - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain > OEM Issues

OEM Issues Original Equipment Repairs and/or Problems

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  #1  
Old 08-21-2008, 10:33 AM
Trailluvr Trailluvr is offline
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Cylinder 5 Misfire - which one??

I'm new here, so just wanted to say hi to everyone, and had a question that will likely be easy for many. I just purchased an '02 Trailblazer with 98k. So far, I LOVE the truck!! I picked it up for 4 grand as well...so that didn't hurt!!

The guy I bought it from told me it was running a little rough, and that he just had the spark plugs changed. When driving it home, I noticed it would run rough and feel like it was missing at stoplights. I brought it down to Advanced Auto Parts and they hooked it up to the scanner and it had a "cylinder 5 misfire" code. I ordered a new coil, but am not sure which one to replace. I have read on here that the cylinders are numbered 1-6 from front to back, and that the firing order is 1-5-3-6-2-4. Would that mean the one reported as cylinder 5 by the error would be the 2nd from the back, or the 5th cylinder in the firing order which would be cylinder 2, which would be the second from the front???
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  #2  
Old 08-21-2008, 11:24 AM
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Robert1101 Robert1101 is offline
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1 to 6 is front to rear. And welcome to the site. Lots of information on this board.
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Old 08-21-2008, 11:56 AM
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i think its referring to the 2nd from the rear.
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Old 08-21-2008, 12:39 PM
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bolacha bolacha is offline
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From what I remember, and correct me if I'm wrong anybody, but I believe on the valve cover it numbers the cylinders, so just look for the number 5 and replace that plug. If it still mis-fires you may want to check your connections to the coil packs. Then if the problem still persists to happen try replacing the coil pack. A good way to check if it's the coil pack switch it with another one say 4 for example if that one misfires then its fair to say the coil pack is bad.

WARNING: these are aluminum heads, so when doing any of this work make sure your engine is cool. If not you will strip out the threads.
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Old 08-21-2008, 03:35 PM
Trailluvr Trailluvr is offline
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Thanks for all the info!! I went ahead last night and replaced the coil that is second from the back, which I believe would be #5. I just wanted to make sure I did the correct one, as my brother cast some doubt in my mind. . The plugs were just replaced prior to be purchasing the truck. Unfortunately, as soon as I had the issue and then ordered the coil (after replacing the air filter and running some injector cleaner through) the rough idle went away and the SES light never came back on. I had it scanned once more prior to installing the new coil and it still had an error stored for a misfire on cylinder 5. It is running great now. I am going to clean the throttle body tonight just for fun, and hopefully by having the battery unhooked it will clear any stored codes.....
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Old 08-21-2008, 05:14 PM
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Super 88 Super 88 is offline
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Yes, the cylinders are number 1 - 6 with 1 being the front one, 6 being the back. The firing order is just the order that the cylinders fire. This was much more important in the days of distributor caps and wires.
When the code states #5 misfire it means that the #5 cylinder is misfiring (second from the back)
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  #7  
Old 08-21-2008, 05:59 PM
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Be sure to re-seal the back hood gasket when making the repairs. There was a TSB out for '02 through '03 or '04 vehicles, that mentioned that rain/moisture past that seal can result in coil failure. They issued a revised rubber seal with a secondary gasket that lies between it and the chasis....a bead of silicone under the rubber strip would provide the same effect.
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  #8  
Old 01-18-2012, 04:13 PM
CWH2012 CWH2012 is offline
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Smile Thanks!

Gentlemen and Ladies (just in case), I just wanted to thank everyone for the posts. This site has been more than helpful in diagnosing and fixing my ignition problem with my 2002 GMC Envoy (167K miles). I have loved this vehicle since the day we bought it. Was feeling a miss in the motor and had it checked out. Said it was a misfire in #3. I changed the plugs, cleaned the throttle body while I was ther and unhooked the battery cable during the whole thing based on the advise from this forum. It did turn out that I had to replace the ignition coil and it runs like the day we bought it. P.S. I found a new ignition coil on line for under $40 including shipping. Thanks again for everyone's input! -CH
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