2005 Chevy Trailblazer Runs Rough at Idle With No Compression

#1 cylinder in my 2005 Trailblazer has no compression. I applied air pressure and it sounded like the exhaust for no air came out f the throttle body. There was air coming out of my # 5 cylinder with the #1 at TDC. wanted your opinion on if you think it is an exhaust valve not seating?

Yes, I would think that is your problem. Those cylinder heads on the inline 6 engines have been known to have problems with valves. Usually not repairable, and will require cylinder head replacement. Do all of the other cylinders have good compression?

Also what is a variable valve timing solenoid and would it cause this? cheaper route. it is the famous Chevy 4.3l.

OK, so you’ve got an old style Blazer then, right?

Sorry Internet problems

That’s OK, so you have the ‘old’ style Blazer, correct?

No, it’s an 2005 4.2L.

You said 4.3 in a previous comment, I thought you had the V6, but you DO have the inline 6?

I have the inline 6 cylinder engine. I ran a compression test with over 220 psi in the 2-6 but zero in #1

As for the variable timing solenoid, also called a cam phaser….that would NOT cause you to have an issue like you’re facing. Looks like the head will have to come off.

Was I supposed to pull the valve stem out for the pressure gauge in order to run the test? I am fishing for simple solutions.

Leave the valve stem in to do a compression test, and take it out to put air in the cylinder….you seemed to have done it correctly. Unfortunately, there is NOT a simple solution to your problem. Most likely will need a new cylinder head!

Thank you. lastly when applying pressure, would it force the oil that I used to verify it was a faulty head back through the piston rings?

Not usually, unless they are really loose, in which case you would have heard air coming out the oil fill or dipstick tube.

Ahh. Didn’t hear that. So the air coming out of the #5 was probably do to the open exhaust valve in the #1 through the valve cover to the #5 valve?

If you had number 1 cylinder at TDC, neither valve should have been open. You mentioned hearing air out the exhaust, which would tell me a burned valve or a valve that is not seating. It should not have transferred through cylinders.

I wonder if I should have turned the crank shaft a bit more on the down for the #1 to be at actual TDC? I stopped right at the top of its stroke. air was definitely coming out of the exhaust though.

Well, with zero compression, and I’m sure you have a misfire on that cylinder, there is really nothing to re-check. It’s a mechanical problem of some kind in the head itself.

Borescope came out good for the piston and the walls. some gunk but no holes.

I’ve seen this over and over on the inline 5 and 6 cylinders in the Trailblazers and Colorado’s

Well computer is saying 0301 I think.

Yes, that code is for a misfire on #1 cylinder.

Now the decision to get an engine or head. I think the engine is only a couple hundred more. how long can you run it like that. or would the valve possibly stay open and contact the piston. what might be some of the outcomes to run it fr a bit longer?

Do you have a lot of miles on the engine as of right now?

It has 85000 miles.

It doesn’t really hurt to run it, you’ll just have to deal with the misfire and lack of power. The only thing would be, that the fuel getting dumped into #1 and not burned would end up in the catalytic converter which can damage it.

Was looking at car-parts.com

If the engine was maintained well, and still in good shape I would probably just go with a head. Otherwise I’d probably do a new engine.

Oh. alright. thank you for your opinion. stumbled upon this live chat and could have used it for some time. will have to save it to my favorites. take care sir/ma’am.

You’re welcome, glad to help! Come back anytime you need a question answered!

Will do.

And check our forums out too, they can be helpful.

I also have a 1994 Ford I am sprucing up for towing. NO tow package. I was jus looking, is there an application on the Iphone that has this live chat feature as well?

Not at this time. This website is mobile ready and we are looking into making a mobile phone app, so check back!

Alright ty very much.

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