- Jan 7, 2012
- 86
My 2004, 4.2 I6, Trailblazer LT with 135,000 miles has been acting peculiar for the past year. It has a tendency to misfire occasionally and gives either a P0300 (random misfire) or P0302 (cyl2 misfire) separately or together from time to time. This can happen for days in a row or once a month. It also ONLY occurs when I leave the truck in idle, never occurring in gear or at speed. It has recently cropped up again for the past few days and I now have adequate time to tackle it once and for all!
Steps taken:
-Replace plugs, all brand new as of 6 months ago. No effect.
-Move coil pack. This resulted in a P0300 again but never another code that would isolate a cylinder.
-Replace coil pack. I figured I'd try it anyways since the P0302 never came back. No effect.
/////Didn't have a problem for some time, figured it was ok. Problem came back and went away a few times over the next few months. Some point in here I took it to the dealer and they looked at it and wanted thousands of dollars to fix a "small timing issue" without providing additional details. I said screw you (in nicer words)./////
-Replace o2 sensor, it was time to anyways. This resulted in a P0171 (system lean) and persistent high idle of 900. I cleared the code and it went back to normal. No effect.
-Replaced camshaft position actuator solenoid. There was oil in the connector and a damaged screen inside. No effect.
/////At this point, I have not gotten a code after a few hours idling, perhaps the gremlin got scared temporarily again or maybe the issue is really fixed. However, now the engine tries to die while at idle, with no code showing up./////
Current situation. After a few hours idling, there are no codes however the truck tries to die, rpms jump down and back up, every few minutes while idling in park or neutral.
Anyone see anything interesting that indicates the problem? I don't mind throwing a few hundred dollars at things that really should be replaced every decade anyways, but I would like a definitive solution eventually, especially before the problem becomes worse.
A little more information: the truck tends to misfire more often when idling on an uneven surface. Like when parked on the side of the road there is the 10-15 degree slant sideways, 30 minutes here would almost always guarantee a misfire code. The misfires were also never what I would consider serious. There would be a slight wobble in the engine that could be felt in the car, but it was only momentary and only felt every few seconds. It is noticeable however, as the vehicle is usually so smooth that when working correctly, I can forget it's running if there's music playing. Also, there is no liquid of any kind in the spark plug chambers.
Thanks in advance!
khill
Steps taken:
-Replace plugs, all brand new as of 6 months ago. No effect.
-Move coil pack. This resulted in a P0300 again but never another code that would isolate a cylinder.
-Replace coil pack. I figured I'd try it anyways since the P0302 never came back. No effect.
/////Didn't have a problem for some time, figured it was ok. Problem came back and went away a few times over the next few months. Some point in here I took it to the dealer and they looked at it and wanted thousands of dollars to fix a "small timing issue" without providing additional details. I said screw you (in nicer words)./////
-Replace o2 sensor, it was time to anyways. This resulted in a P0171 (system lean) and persistent high idle of 900. I cleared the code and it went back to normal. No effect.
-Replaced camshaft position actuator solenoid. There was oil in the connector and a damaged screen inside. No effect.
/////At this point, I have not gotten a code after a few hours idling, perhaps the gremlin got scared temporarily again or maybe the issue is really fixed. However, now the engine tries to die while at idle, with no code showing up./////
Current situation. After a few hours idling, there are no codes however the truck tries to die, rpms jump down and back up, every few minutes while idling in park or neutral.
Anyone see anything interesting that indicates the problem? I don't mind throwing a few hundred dollars at things that really should be replaced every decade anyways, but I would like a definitive solution eventually, especially before the problem becomes worse.
A little more information: the truck tends to misfire more often when idling on an uneven surface. Like when parked on the side of the road there is the 10-15 degree slant sideways, 30 minutes here would almost always guarantee a misfire code. The misfires were also never what I would consider serious. There would be a slight wobble in the engine that could be felt in the car, but it was only momentary and only felt every few seconds. It is noticeable however, as the vehicle is usually so smooth that when working correctly, I can forget it's running if there's music playing. Also, there is no liquid of any kind in the spark plug chambers.
Thanks in advance!
khill