If a coil or plug is bad, the MIL light will illuminate and a code will be stored. Trailblazers, Envoys etc with 4.2 liter L6 allows rain to leak past hood gasket and pool in spark plug wells. The water will melt plug electrodes or short out coils. Delphi coils are a must. Cheaper are available but you get what you pay for.
motor mount , vvt selonoid , camshaft position sensor , crankshaft position sensor , and im sure the knock sensors are going crazy , you can pull one coil wire at a time , if it stops when one is pulled that's you bad coil or plug , if not the coils and plugs are good ...
I can't really describe it to you, but I used a little tweaker screwdriver to release the clip. I'm not going to lie to you, it's a little finicky. You have to take out the retainer before you can take the clip off the coil.
My 1st guess without scanning the pcm would be bad coils or sparkplugs. If there was any oil in the intake I could say the pcv hose underthe manifold needed to be cleaned. Could also be the cam sensor. Hard to say without knowing the codes or any recent service records. I would also pull the vvt solenoid if there were any timing codes just to see if it was clogged.
Good troubleshooting info. I'll have to try the IR gun on one of my projects that's misbehaving. Btw, did you have a check engine light on when this happened?
I replaced all spark plugs and coil packs. i have no oil in any of the wells. i dont know why but the idle still fluctuates. idk if i need to unhook battery for a while and dump memory and try to reset everything. idle still feels like its trying to find sweet spot when im parked and not moving.
Your problem is a little different than a dead miss. You might want to give your throttle body a good cleaning. Check for vacuum leaks, etc. Do an engine scan and see if anything isn’t right
@@GroundhogzGarage idk ive tried everything. it was clogged cat. its straight piped now still ran rough. cleaned the intake too already. thats why i changed spark plugs and coils. idk what else to do. What your opinion on seafoaming intake?
@@GroundhogzGarage It was for me, the first time I replaced the plugs, the wire bundle over the #1 Cylinder was so tight, that I had a hard time getting the coil back on correctly and was getting misfires. Took me about 3 or 4 attempts before I finally got it on correctly. Now after 18+ years, and 445K miles, the wire bundle has loosened and it is easier now.
I have to ask, does (or did) your trailblazer make like this very faint sort of knock? Kind of sounded like it's towards the back or middle section of the engine? Trying to chase down a noise.
When the Atlas engine line was finally up to go time for assembly it was discovered that the manifold screws (both sides) were about a little over a mm too long. They bottom out before the manifolds are really tightly set on. They rattle loose and leak over time, & the exhaust side ends up fracturing if ignored too long. Replace with slightly shorter screws is the best remedy. They suck in air causing lean mixture or leak exhaust into the engine bay and rough running and noise.
Just to mention, this has an electrical throttlebody. you dont want to pry it open to clean. Have someone you trust press the gas when your cleaning when only the electrical is turned on. dont have car started but turn key halfway. 👍
F U E L I N J E C T O R S might also be one cuz I also put in new ngk plugs and my truck started idling like a cartoon jalopy after new plugs and ngk coils
If it wasn’t running like that before you put the plugs and coils on, you introduced a new problem. Make sure all your plugs are gapped and seated. Make sure you have the coils seated on the plug correctly. Did you put some dielectric grease on the boots of the coils? Do you have the harness connected to the coils correctly?
