LARRY BRUDZYNSKI Posted August 30, 2010 Share Posted August 30, 2010 Hey guys, scratching my head on this one. My delivery truck. 05 Colorado 2.8 L4 misfire on #4 coil pack. We just put plugs and coil boots on it 30K ago. Plugs were burnt as if it's been running lean. We also replaced the T-body due to a bad TPS. We got new plugs and a new #4 coil pack. It still has a #4 coil pack code and still is missing on that cyl. We swapped coil packs and still have the cyl #4 code. We inspected the harness as far as we could, no chafing, connectors are good and clean. Any ideas???? Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted August 30, 2010 Share Posted August 30, 2010 Does it have compression and fuel in that hole? Coil pack code? Open circuit on the primary, or dead hole? I'd scope the coil return and see if the PCM is activating the coil. You "might" even be able to do this with a test light- probe the coil return and it should be blinking really fast while running. (there will be two leads, one will be B+, the other is coil return) Compare it with the coil return from another cylinder as a "known good". Poor man's scope..... Quote Link to comment Share on other sites More sharing options...
Aaron Posted August 31, 2010 Share Posted August 31, 2010 Yeah, or jam a Noid light in it. It seems to me I dinged one for a PCM, then it turned into Emissions warranty or something, and went back to the Chevy store, and they put a PCM in it, all was good. It was for a misfire, the coil pack wasn't being fired by the PCM... I don't recall the codes, sorry Larry Quote Link to comment Share on other sites More sharing options...
Aaron Posted August 31, 2010 Share Posted August 31, 2010 Yeah, and is it a primary code or a misfire code? If it looks lean in that hole... is the injector working? Is it getting fuel? I can give you a hand with some of that junk next time I'm over there, if you can convince the powers that be to let you drive it home over the weekend Quote Link to comment Share on other sites More sharing options...
LARRY BRUDZYNSKI Posted August 31, 2010 Author Share Posted August 31, 2010 Drive it home???? It's a four banger with a miss. Drives more like a friggin Ruttman minibike now. I'll take a look at the other things tomorrow. My repair shop is draggin their ass on this one. This sucks, I'm expected to jump thru hoops for them and I'm getting the unwanted step child treatment. And to think they get pissed when I farm these out...... Quote Link to comment Share on other sites More sharing options...
Fredsvt Posted September 1, 2010 Share Posted September 1, 2010 The 2.8 I4 and 3.5 I5 suffer from the same issues as the 4.2 I6 do. Did you clear the codes prior to starting, these will disable the injector if it detects a cat damaging misfire and won't re-enable it until codes are cleared. Been there with a Trailblazer with a bad coil. Bright white plugs are a normal thing to see on these. You should check compression, and running compression. They have nasty issues with burned valves, dropped or bad guides. And bad heads. If you have to take it apart, be very careful to rattle all the head bolts with an air hammer or use a good dead blow hammer and a nice solid punch. Otherwise the head bolts snap off in the block or head making removal a joy. There's also a timing chain holding tool so you don't have to remove the front cover. If you choose to remove the front cover, it can be much easier to pull the motor. Quote Link to comment Share on other sites More sharing options...
LARRY BRUDZYNSKI Posted September 1, 2010 Author Share Posted September 1, 2010 Alright....Somebody knows something about them. Will clear the codes in the A.M. and look deeper. Hope It doesn't go any further. Thing that kills me is it was running good and then it wasn't overnight. Thanks a bunch. Will post back tomorrow on my finds. Quote Link to comment Share on other sites More sharing options...
LARRY BRUDZYNSKI Posted September 3, 2010 Author Share Posted September 3, 2010 Update......Cleared codes and ran, still has a miss. Threw a P0300 now within 2-3 minutes. Random misfire now. Not throwing the P0304 anymore. It looks like it can be due to multiple problems now. My shops next throw at the misfire....Must be injectors, so they pull them we put them on the stand and of course....Perfect spray pattern and flowing great. We ultrasonic clean them anyways and now we are waiting for intake gaskets and seals. Parts won't be in until tomorrow. Other probables include bad EGR,MAF,vac leak and so on. This is getting old.....All they are doing is throwing hopes and wishes at it. With everything I do at work including getting deliveries out, this is causing some real static and the shop. To top it off our other parts truck went down with brake problems today. It's fixed now but I had to farm it out to get it done. My boss isn't real happy about that, but WTF I had to do something. Needless to say the Shit sandwiches are flying today. Quote Link to comment Share on other sites More sharing options...
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