She’s been sitting a while!!

[Jhill7980]

Hello everyone! I recently took over stewardship of my girlfriends 04 Trailblazer LT. she’s got 148k on her and has been sitting for over a year.
Currently she is giving me a p0300 code and runs pretty damn rough. Have checked for vacuum leaks to no result. When driving she lurches when shifting and doesn’t ever seem to make it out of 3rd gear (afraid to push her too hard).
Since I gotten it, I’ve done the following routine things.
-crankcase flush with two oil changes
-transmission fluid drain, filter change and refill
-new spark plugs
-new serpentine belt
-new battery

All fluid levels are as they should be.
I am in no way an expert, but can figure most things out with some research and help.

Any ideas of next steps or things to check after vehicle has been sitting for extended periods would be helpful.

Thanks!
Joe


Additionally, she has a good amount of smoke coming from the oil filler cap. Again, not an expert and don’t k ow what all the signs mean, but if I can fix the problems I’d like to try.

 

[I_Shoot_Back]

With how crappy fuel is these days I would suspect she is hurting from stale fuel. I'd drain old fuel and replace fuel filter for sure. Then maybe a strong injector cleaner as they might be a bit sticky?

 

[BrianF]

You could have some blowby, perhaps more than whats acceptable. One can do a compression or leakdown test. Sometimes a few decent oil changes with a quality oil can help free up stuck rings, sometimes you may need to do a piston soak.

Another thing to do is clean the throttle body (lots of topics/how to on this forum). Have the battery disconnected for 30 minutes for it to reset.

P0300 appears to be random misfire. Its possible the coils are on their way out.

 

[Sparky]

When diagnosing misfire issues I like to use my bluetooth OBD adapter and Torque to monitor current cylinder misfire counts to see exactly which cylinder(s) are being problematic.

Smokey stuff coming out of the oil fill cap when running could be a bad sign though. Do a compression test as mentioned, could be another helpful test to pinpoint what's up.

 

[Mooseman]

Usually with an initial P0300, it may take a few regular drives for the PCM to decide which cylinder is actually misfiring and set the proper code. Best thing would be to have a code reader with live data capabality or get a Bluetooth OBD adapter with the Torque app. It may just be one cylinder misfiring. However, as @I_Shoot_Back said, could be bad gas after sitting all this time.