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p0300

  1. General
    Have been having some ongoing issues with my '08 Envoy for a couple of months. Have done a bunch of maintenance which hasn't fixed the problem (but that really needed doing anyway). Have a new theory but just wanted to run it past some other TrailVoy folks to see if I might be on the right...
  2. OEM Issues
    Hey guys, got a 2007 Envoy with 203k miles. Just replaced the spark plugs about 3 months ago with AC Delhi recommended plugs. No issues since but the other day as I got to about 50 mph my check engine light came on and was flashing. Got home and pulled codes, got a P0303 for cylinder 3...
  3. TrailBlazer / Envoy Chat
    I just bought a 2004 gmc envoy from a used dealership. I took it to get the oil changed & to just get an overall look at it to see what all it needs. The mechanic said I need new valve cover gasket & spark plugs. I paid him $700 & soon as I left in my truck it threw code p0300. No check engine...
  4. General
    I have a 2004 Trailblazer 4X4 4.2L. My starter went out. After replacing it, I got a bunch of weird codes like something was unplugged. It also had a misfire in cylinder 2. I replaced the coils and plugs, now I have random misfires. Anybody have a clue where I should start?
  5. Engine Tunes/Mods
    Hello all, I have a problem with my 05 TB 4.2 EXT LT (160,000 miles). Here is the short story: I did an engine swap after the original engine needed a valve job and original block was damaged beyond repair trying to remove broken head bolts. Got an engine from salvage yard. Removed head and...
  6. OEM Issues
    Hey Everyone, I'm new here and have an issue I'd like to get some better insight on. I have a 2004 Envoy, I6 with a continuing misfire P0300 issue. 150,000+ miles. Several weeks ago, the engine started to misfire (blinking check engine light, running terribly). I put in AC Delco plugs about...
  7. OEM Issues
    Haven't been on here in a looong time, but I am having an issue with my 2003 TrailBlazer with the I6 engine. A couple of days ago, it seemed as if it was having some power loss while accelerating. Just to confirm, I floored it and it accelerated kind of slower than normal. The acceleration...
  8. OEM Issues
    First, I would like to say hello. I've been a member for several years, but have never posted before. I know there are several forums discussing the P0300 code, but none seem to be similar to my issue. Vehicle: 2007 Envoy SLT with the 4.2l engine. OD: 188,000 About a month ago I decided to do...
  9. General
    Well it seems I have the dreaded P0300 misfire and I'm having a terrible time tracking it down. I'm in a bit of a tight situation right now and can't throw money at it to see if coils will fix it so I'm hoping to find a few hints and help here. It's a 2004 4.2L 2wd. The back story is that I...
  10. Engine Tunes/Mods
    My 2003 TB all of the sudden started running bad at a stoplight. Check engine light flashed and then came on steady. Checked code when I arrived home. P0306, misfire cylinder 6. After going through the forum I decided to swap ignition coil 2 and 6 to see if the problem would move to cylinder 2...
  11. OEM Issues
    So I have a 2007 TB with about 113k miles, it has the I6 engine. I am very familiar with these engines as in the past I already have had an Envoy for many years and put over 175k miles on it. A few months a ago I started to get the cylinder 4 misfire code and I read about every forum on here...
  12. OEM Issues
    Okay, i have been reading these forums for several years and they have been a huge help in diagnosing and fixing the issues that my 02 TB has presented... until now. This is going to take a little bit to explain so bear with me. About a year ago, i had some missfire issues and ended up...
  13. Introductions
    Ok I have a 04 TB with about 172,000 miles Recently it has started to misfire . I took it had a code p0300 So I replaced the plugs "boots" and found Coil #1 was bad and replaced it. It made it Run better but still shows same code. I have ran a couple bottle of Lucas Fuel Treatment...
  14. OEM Issues
    Well this is a long drawn out story that is worth writing and I thought I'd take a few minutes to share some experiences worth hearing about. All started a week ago, I was towing my RV back from Indiana and the TB started overheating, Check engine light was on and it turned out to be a bad fan...
  15. OEM Issues
    Whats up, I am having problems with the 05 Tb. I have changed my spark plugs, cleaned my throttle body and changed 2 coil packs and I am still getting a p0300 error. Also, if I get the rpm's over 2k the ses flashes. I have stopped driving it. It all started when it was pouring down rain and...
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