Hello all. New to the whole Trailblazer/gmt platform. Purchased a 2002 LTZ a few months back and have no problems. Until now. Drove to work fine yesterday and upon leaving work after a short downpour, truck had severe misfire. Limped it home with flashing CEL. scanned and had a random/ p0300 code. Figured water had gotten on coil 4 as I had read happens. Pulled all coils and they were all completely free of any water and oil. have had an intermittent cam position code in the past, but no driveability issues previously. Removed and cleaned the cam position sensor, along with the vvt solenoid. Upon removing the vvt solenoid, I noticed it was extremely difficult to remove. and also noticed the entire outer body, would spin. Is this normal? with the help of a small prybar, it finally slid out and had surprisingly little gunk on the screens. Cleaned and replaced, reconnected battery to try and reset computer and no change. Still ran like poo... couldn't get a code while running in driveway, so took a short drive to the gas station, and had cel flashing and an obvious miss.. p0300 returned. Tried playing around with vvt and cam sensor while running and when I disconnected the vvt plug while running, solenoid code appeared. So, I'm guessing that is "working", but when I unplug the cam sensor while running, no cel and continues to run the same, like poo. (No change from plugged in to unplugged) so am I seeming to be correct that I should look into the cam sensor first? Have an hour drive to visit family in the AM and am going to try and hit up the LPS when they open, and just looking for opinions if you all with more experience than myself think I'm going the right direction. Thanks
2002 bad misfire.
- Thread starter stir77
- Start date
Wooluf1952
Member
In case you haven't heard:
https://gmtnation.com/forums/threads/welcome-to-gmtnation-com-heres-the-story.218/
The plug wells might be dry, but the coils could be bad. How many miles on the truck? Have the plugs been changed to the new AC Iridium 41-103? (Thanks Mooseman) Also, running with the CEL flashing can/will cause the cat to clog.
Last edited:
Truck has 173,xxx miles. Plugs were changed approx. 25,000 miles ago according to paperwork. 41-103s. Driving while flashing has been very limited. I have about a 5 minute commute to work. I understand that coils could be bad, but to lose more than one at the same time? That's whats making me think its elsewhere. Its not an isolated single cylinder miss. Also, that cam sensor has thrown the engine light a number of times before, I just never noticed a driveability issue, (miss, studder, sluggish response.) Ill try to ohm out the coils today before I leave this morning. Thanks again,
Mooseman
Moderator
@Wooluf1952 did a typo. They are supposed to be 41-103 so you're good there.
It should never flash. This would eventually kill your cat. It is very unlikely that they are all failing however two failing would throw a P0300 as it can't determine which one is misfiring and that has been seen before. You would have to get either a high end scanner or a Bluetooth OBD adapter with an app like Torque to read misfire data.
Other things to check: intake manifold bolts, throttle body bolts, vacuum hoses, intake hoses, fuel pressure.
When you pulled out the CPAS and cleaned the screens, did you check for oil in the connector? At that mileage, they usually fail so it might not be a bad idea to replace it. Not super expensive but worth shotgunning. It's normal that it can spin on the holding clamp but not the plastic connector end in the body. Stay away from Dorman. ACDelco or Delphi are recommended.
It should never flash. This would eventually kill your cat. It is very unlikely that they are all failing however two failing would throw a P0300 as it can't determine which one is misfiring and that has been seen before. You would have to get either a high end scanner or a Bluetooth OBD adapter with an app like Torque to read misfire data.
Other things to check: intake manifold bolts, throttle body bolts, vacuum hoses, intake hoses, fuel pressure.
When you pulled out the CPAS and cleaned the screens, did you check for oil in the connector? At that mileage, they usually fail so it might not be a bad idea to replace it. Not super expensive but worth shotgunning. It's normal that it can spin on the holding clamp but not the plastic connector end in the body. Stay away from Dorman. ACDelco or Delphi are recommended.
Misfire fixed. Scanned yesterday morning and finally showed a p0302. So I switched 2 &3 and after numerous scans of p0300 a p0303 finally showed. Changed coil out and running like new again. Yes there was a bit of oil in the vvt plug. So that is next on the agenda to change.. thanks for your words of wisdom. So far love the trailblazer compared to the mountianeer I retired. Pulls my 20ft cuddy cabin boat without an issue...
