Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum banner

1 - 20 of 23 Posts

·
Registered
2002 chevy trailblazer_lt
Joined
·
11 Posts
Discussion Starter · #1 ·
I am having a problem with misfiring that I can not pinpoint. When the vehicle is first started the engine runs fine. However after it warms up a little the engine misfires when I come to a stoplight and it also misfires when I am cruising on the highway at around 2100 rpm. I have a code ready and when I scan the vehicles computer there are zero codes showing up. Also there are not any warning lights on the dash and all gauges read normal. I have already changed the spark plugs which helped a little but not much. The throttle body didn't seem dirty at all just a very very light unmeasurable amount of soot or crap or whatever you want to call it. Anybody have any suggestions or ideas of what might be causing this misfire problem???? Thanks

2002
chevy trailblazer Lt
85,000 miles
 

·
Banned
2004 gmc
Joined
·
26,181 Posts
Plugs, flaky wiring, fuel injectors, or bad compression are the typical culprits.

Edit: Oh, and what plugs did you install?
 

·
Registered
2002 chevy trailblazer_lt
Joined
·
11 Posts
Discussion Starter · #3 ·
I just installed some off brand name plugs....Neither auto part store in my town had the OEM ones so I just took the cheap ones to try to get an idea if the plugs where the problem or not.
 

·
Banned
2004 chevy trailblazer_ls
Joined
·
335 Posts
Delco 41-103 Iridiums. are the ones that do best as far as spark plugs go prolly the reason.... or i could be wrong but that is what i would do first
 

·
Registered
2002 chevy trailblazer_lt
Joined
·
11 Posts
Discussion Starter · #6 ·
Thanks for the suggestions guys, I picked up a fuel filter today and im going to try it tomorrow, i'm also going to get better plugs. I felt bad putting the cheapo plugs in after pulling out quad platinum plugs but I had no choice at the time..... Thanks for your suggestions.
 

·
Registered
2007 chevy trailblazer_lt
Joined
·
19 Posts
check # 4 coil pac i had this problem it getting wet and rusting i needed to replace mine runs fine now hope this helps you
 

·
Registered
2007 chevy trailblazer_lt
Joined
·
39 Posts
Devlin, toss in a can of SeaFoam cleaner in the gas tank. Stuff works wonders. I also just cleaned out my throttle body. It didnt look bad but once I took it off it had a section of build-up in there that apparently was bad. Once I cleaned it thoroughly it ran fine. I also changed the fuel filter and air filter just in case.
 

·
Registered
2002 chevy trailblazer_ltz
Joined
·
2,063 Posts
Devlin, when you checked the throttle body, did you just look at the front or did you take it off? If you just looked at the front that's not really going to tell you anything.

Along with the plugs (really, use the AC Delco's and no other brand), filter and seafoam, do a proper TB cleaning...look at the link in my signature. Also, don't forget to either disconnect the battery or pull the PCM fuses for at least 1/2 an hour so the PCM resets.

Matt
 

·
Registered
2002 chevy trailblazer_lt
Joined
·
11 Posts
Discussion Starter · #10 ·
Thanks for the suggestions, great step by step mwfaith, . Well changed the air filter, fuel filter,and plugs and it still misfires. I didn't really look to close inside the throttle body so im going to try cleaning that this weekend and run some cleaner gas mix through the system. Hopefully it's just a dirty throttle body. Thanks for the step by step. On a side not... wouldn't a faulty coil show up in the trouble codes?

thanks again
 

·
Registered
2004 chevy
Joined
·
4 Posts
Thanks for the suggestions, great step by step mwfaith, . Well changed the air filter, fuel filter,and plugs and it still misfires. I didn't really look to close inside the throttle body so im going to try cleaning that this weekend and run some cleaner gas mix through the system. Hopefully it's just a dirty throttle body. Thanks for the step by step. On a side not... wouldn't a faulty coil show up in the trouble codes?

thanks again
Not always, the codes are great when they work but don't always rely 100% on it showing or not, I had a bad coil pack that never showed up. If for whatever reason you are not using AcDelco plugs you should be, plain and simple ask anyone around chevy and AcDeloc go hand in hand.
 

·
Registered
2005 gmc envoy_sle_xl
Joined
·
1,029 Posts
Not always, the codes are great when they work but don't always rely 100% on it showing or not, I had a bad coil pack that never showed up. If for whatever reason you are not using AcDelco plugs you should be, plain and simple ask anyone around chevy and AcDeloc go hand in hand.
Just curious. The CEL never came on or you never had a CEl and codes to pull?
 

·
Registered
2002 chevy trailblazer_lt
Joined
·
11 Posts
Discussion Starter · #14 ·
Well I cant believe it and I'm still skeptical if the problem is fixed or not but after changing the plugs, fuel filter, and air cleaner I drove my truck to work today.
Still idled rough at stop lights and misfired while cruising the highway at a steady speed. After work I went directly across the street and bought a bottle of fuel line cleaner (additive for gas). The entire ride home the truck ran better than it has in 2 weeks. and just to make sure I sat in a burgerking parking lot for about 20 minutes eating my food and starring at my tack. Didnt miss fire or stumble at all!


keeping my fingers crossed and happy I don't have to buy a new coil pack. I'm still going to check out my throttle body this weekend for a more thorough cleaning
 

·
Registered
2005 gmc envoy_sle_xl
Joined
·
1,029 Posts
P.S. great site you all have here, very informative and handy.
Congrats. Many here swear by Techron Concentrate, Redline SL-1, or any other fuel system cleaners that have a lot of PEA in them. The PEA cleans the combustion chamber, valves and tops pistons of deposits. I started using the Techron a month ago and have seen positive results. I would recommend once a month treatment until no more improvement is noticed, then once every six months or so for preventative maint. Keep an eye on the mileage.
 

·
Registered
2003 chevy trailblazer_ls
Joined
·
163 Posts
Thanks for the suggestions, great step by step mwfaith, . Well changed the air filter, fuel filter,and plugs and it still misfires. I didn't really look to close inside the throttle body so im going to try cleaning that this weekend and run some cleaner gas mix through the system. Hopefully it's just a dirty throttle body. Thanks for the step by step. On a side not... wouldn't a faulty coil show up in the trouble codes?

thanks again
If your going to run fuel cleaner run a can of BG 44k, BEST thing on the market hands down.... I run it every other oil change. And I run BG MOA int he oil every oil change.

As far as your problem I would lean to a bad Coil Pack. I had a similar issue, popped a new coil pack in the last Cylinder and BAM fixed! lol
 

·
Registered
2003 chevy trailblazer_ls
Joined
·
163 Posts
I just saw that you believe you may have got it fixed... Hope you did!

As stated above run some BG44k and you will be set! Run it on about 1/2 a tank and then run it until empty.. :cool:
 

·
Registered
2005 chevy trailblazer_lt
Joined
·
26 Posts
check # 4 coil pac i had this problem it getting wet and rusting i needed to replace mine runs fine now hope this helps you
Do you have any idea why #4 goes bad on our trucks? All of my other ones look brand new and #4 is corroded to hell. I'm compelled to swap mine out, but I am curious to know why that one seems more prone to issues.
 

·
Registered
2005 gmc envoy_sle_xl
Joined
·
1,029 Posts
Do you have any idea why #4 goes bad on our trucks? All of my other ones look brand new and #4 is corroded to hell. I'm compelled to swap mine out, but I am curious to know why that one seems more prone to issues.
It's been posted here many times before but here is the problem. There is a TSB (to lazy to lookup my Alldatadiy stuff). Basically the hood seal on the traling edge leaks water down into the valley where the plugs are (mostly #4). The coils are not air tight, they have a small slit to allow for air/ or water to flow into the plug galley. Get the TSB fixed by getting a new seal and say byby to the rusting of the plugs/shorting out/misfire issue. By this time the coil may have been damaged so swap it out with another and recheck the coil after putting in new plugs (all six)
 
1 - 20 of 23 Posts
Top