2004 Trailblazer rough running engine

[@kennethmakuta7575]

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.

[@DBZLEGENDS]

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.

[@GroundhogzGarage]

You’re awesome. Thanks for posting your thoughts.

[@DBZLEGENDS]

@@GroundhogzGarage please let me know what was the issue. Im curious to know regardless weather i was right or wrong.

[@GroundhogzGarage]

@@DBZLEGENDS #2 coil

[@cherylflemmer4898]

Hmm I've replaced vvts ignition coils spark plugs cam shaft position sensor map sensor heat sensor still having multiple misfire

[@robertKnight-k3k]

I have the same thing getting oil in my air box I've been trying for weeks to get it to run right need help 😢

[@kevinpunk9362]

I had the same problem on my 2004 Changed my #6 coil and that was it

[@MyNameisntEarl]

Did the same thing today, the miss is mostly gone but the motor is still rocking like this slightly

[@LawrenceHollywood]

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 ...

[@mikenovicky]

Can’t hurt those vortecs!

[@dispodan2399]

Love my trailblazer, 250,000 , Delilah (my truck) is a good ol girl. Great engine if you listen to her

[@GroundhogzGarage]

We would take ours to Florida all the time. Down and back and only burn a fraction of a quart of oil.

[@1jeffr]

The #1 Cylinder is the hardest coil pack to replace, I would put the new coil there.

[@GroundhogzGarage]

It isn't THAT much harder to replace.

[@1jeffr]

@@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.

[@GroundhogzGarage]

@@1jeffr Your point is valid. I know what your talking about

[@fredrod000]

Mine had burnt exhaust valve #2cylinder. Massive amount of work to pull the cylinder head

[@GroundhogzGarage]

Pulling a cylinder head is typically a lot of work. That’s an out of the ordinary problem.

[@450mijaou1]

I believe mine has the same issue. Did you have any smoke?

[@gguilliams14]

Just worked on my 06 envoy. 4 out of six plugs were filled with water. Thinking it is from a leaking seal under hood.

[@maqnati3678]

Build it back with caulk or silicone and put a piece of cardboard on it so when you close the hood it won’t stick and you’ll be able to see if that is where it’s coming from by the wet cardboard on inside

[@mzlenna19]

Camshaft sensor

[@TattedTommysTv]

MAP sensor from dirty throttle body replace map and clean throttle body bet it fixed or fixes it .. Did you ever figure it out?

[@GroundhogzGarage]

Bad coil

[@sayleebocook6293]

Mine is doing the same thing so do I need to tune up let me know please

[@tylersanders8853]

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.

[@GroundhogzGarage]

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

[@tylersanders8853]

@@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?

[@tomsteiner1466]

might try looking at the vvt solenoid@@tylersanders8853

[@pjwarren4038]

Highlights magazine!! Lol😅

[@nickd.7267]

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.

[@GroundhogzGarage]

No. No knocking noise. Could be a broken engine or transmission mount.

[@B-rads]

Just bought a 3 Trailblazer if I had this issue I will I have no help thank you

[@kencox8041]

O2 sensor?

[@robertKnight-k3k]

I have the same I put in a use throttle body twice and clean my plus it ran ok but now it's doing the same thing 😢

[@GroundhogzGarage]

Replacing the throttle body is kind of an exotic fix. Plugs and coils are much more likely to be a problem.

[@RetroCaptain]

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.

[@tylersanders8853]

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. 👍

[@opentoreason1975]

How did you remove the retainer clip on the plug? Hands were covering procedure on video.

[@GroundhogzGarage]

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.

[@StickyWhistle76]

Cam position sensor

[@g3garage]

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?

[@GroundhogzGarage]

Dang it, I wish I would have mentioned that, but yes, I did have a check engine light.

[@g3garage]

​@@GroundhogzGarage No worries, still a great video. "Process of elimination" is my mantra lol.

[@davidadrianmorales6585]

if the check engine is flashing, its a coil. that could also mean the spark plug is bad too which is why the coil went bad so check both

[@erahelp]

Intake manifold gasket

[@benledesma847]

Fuel regulator

[@althomas8649]

Coil

[@RachealOlvera]

Temp sensor

[@Troy-yl1jr]

Throttle body

[@AdamRocha-n3u]

A bad pvc. Valve. Or your camshaft is bad.

[@Krunchyjclown]

I hate to be the one to inform you of this but, Your truck has been listening to Van Halen.

[@KirbyLouis]

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

[@GroundhogzGarage]

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?

[@KirbyLouis]

@@GroundhogzGarage fuel pressure regulator