# Misfiring problem **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** chevrolet, trailblazer\ **Created:** [August 7, 2012, 1:47pm UTC](https://community.cartalk.com/t/misfiring-problem/73967 "2012-08-07T13:47:14Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![brizzo84](https://avatars.discourse-cdn.com/v4/letter/b/6f9a4e/32.png) [@brizzo84](https://community.cartalk.com/u/brizzo84)\ **Post date:** [August 7, 2012, 1:47pm UTC](https://community.cartalk.com/t/misfiring-problem/73967/1 "2012-08-07T13:47:14Z")
I changed my plugs recently in my 2004 Chevrolet TrailBlazer 4.2l I6 with the coil on plug setup, and now it is misfiring and hesitating when I hit the gas. All the spark plugs have the proper gap and torqued down properly. I tried tightening down the ignition coils and on one I snapped the bolt. Of course my truck is staying parked until I replace the part which I have to order online due to being stationed in Germany with the US Army. The only thing I can think of as far as the misfiring is not having a proper seat with the coils, my question is does anyone have any ideas on how to get a better seating or if there are any other possible issues I could have over looked at all? ---
**Author:** ![RemcoW](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/remcow/32/2471_2.png) [@RemcoW](https://community.cartalk.com/u/RemcoW)\ **Post date:** [August 7, 2012, 3:41pm UTC](https://community.cartalk.com/t/misfiring-problem/73967/2 "2012-08-07T15:41:44Z")
What happens when you swap that one original cable/coil back in? ---
**Author:** ![brizzo84](https://avatars.discourse-cdn.com/v4/letter/b/6f9a4e/32.png) [@brizzo84](https://community.cartalk.com/u/brizzo84)\ **Post date:** [August 7, 2012, 5:25pm UTC](https://community.cartalk.com/t/misfiring-problem/73967/3 "2012-08-07T17:25:43Z")
its still the original coils, all i changed where the plugs ---
**Author:** ![UncleTurbo](https://avatars.discourse-cdn.com/v4/letter/u/e9a140/32.png) [@UncleTurbo](https://community.cartalk.com/u/UncleTurbo)\ **Post date:** [August 7, 2012, 6:55pm UTC](https://community.cartalk.com/t/misfiring-problem/73967/4 "2012-08-07T18:55:55Z")
The rubber boots with springs in them that connect the plug to the coil can be bad. If you had a NAPA store close by they sell sets of new boots. Not sure how to source them in Germany. ---
**Author:** ![brizzo84](https://avatars.discourse-cdn.com/v4/letter/b/6f9a4e/32.png) [@brizzo84](https://community.cartalk.com/u/brizzo84)\ **Post date:** [August 7, 2012, 9:16pm UTC](https://community.cartalk.com/t/misfiring-problem/73967/5 "2012-08-07T21:16:50Z")
i went and double checked the coils, pulled them off for a short second and all 6 where firing, i will look around and i can order parts online. There is a strip lot on post here but i doubt they would have any trailblazers or envoys. i will look into the springs but i think i do remember when i pulled out the old plugs they where close to a .050 gap whereas the manual i have says they should be a .042, i will be double checking tonight or tomorrow. i will be trying some injector cleaner and check the fuel filter also just to be safe. the vehicle has just over 100,000 miles on it, i want to say 100,400 is about the more accurate number. i do thank every one who has posted and future posts if any. thank you. matt ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [August 7, 2012, 9:58pm UTC](https://community.cartalk.com/t/misfiring-problem/73967/6 "2012-08-07T21:58:26Z")
Other than wondering about that snapped COP bolt (did you seriously overtorque the holding screws?), and suggesting that you verify that your spark plug parts numbers are correct, I have nothing to add…but I do want to offer you sincere thanks for serving our country. i salute you. ---
**Author:** ![brizzo84](https://avatars.discourse-cdn.com/v4/letter/b/6f9a4e/32.png) [@brizzo84](https://community.cartalk.com/u/brizzo84)\ **Post date:** [August 7, 2012, 11:18pm UTC](https://community.cartalk.com/t/misfiring-problem/73967/7 "2012-08-07T23:18:35Z")
yeah i over torqued it but with the other bolts had no issue, guess that one was about to go lol. and thank you ---
**Author:** ![keith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/keith/32/5518_2.png) [@keith](https://community.cartalk.com/u/keith)\ **Post date:** [August 8, 2012, 3:18am UTC](https://community.cartalk.com/t/misfiring-problem/73967/8 "2012-08-08T03:18:28Z")
Just asking, but did you compare a new plug to an old one for thread length and tip extension? ---
**Author:** ![RemcoW](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/remcow/32/2471_2.png) [@RemcoW](https://community.cartalk.com/u/RemcoW)\ **Post date:** [August 8, 2012, 3:48am UTC](https://community.cartalk.com/t/misfiring-problem/73967/9 "2012-08-08T03:48:50Z")
Good point. ---
**Author:** ![brizzo84](https://avatars.discourse-cdn.com/v4/letter/b/6f9a4e/32.png) [@brizzo84](https://community.cartalk.com/u/brizzo84)\ **Post date:** [August 8, 2012, 6:20pm UTC](https://community.cartalk.com/t/misfiring-problem/73967/10 "2012-08-08T18:20:01Z")
i did on that yes, every thing matched up. the particular model plugs called for ac delco 41-981 had been discontinued, so the ones that where the new model replacement ac delco 41-103 where the ones i bought at the post exchange here, and i also did research before purchasing. i think about it now, could a plug itself be bad?