Well we have an 04 - Trailblazer - 4.2L with 113,000 miles on it. Just noticed some misfiring going on stumbling while leaving a stop. It has the original plugs & boots. So we took it to our mechaninc. Well after tearing half of it down he found the sprk plug bores filled with oil around each plug thus getting up in the spark plug boot shorting out the current firing each plug. He said we are gonna have to pull the valve cover and replace the seals cause they are leaking around the plugs, we said ok. He has never been into one of these yet until now. ( Now here is the problem ). This is a real pain in the butt - NIGHTMARE, Thanks to the engine designers you have to completely remove the computer, pull the engine wiring harness out of the way & lay it on the driver fender apron, remove the alternator, move the A/C line out of the way, remove the plastic intake manifold, remove the fuel rail. Once you get all of this crap out of the way then you can then take the valve cover off. He removed the worn seals, valve cover & intake gaskets & repleaced them with Felpro seals along with new ac delco plugs & boots. This was very labor intensive - 10 hours in total to do this job. Parts cost was $ 144.00 & the labor was 10 hours @ $ 45.00/hr - total bill was $ 604.00. So if you truck is having the same problem & needs this work done be prepared to pay a hefty price tag, if you go to the dealer then it will cost way more than this.

 

$45.00 per hour is very cheap, everything around here is $82.00 and up. Where do you live.

 

Madison, Indiana - they guy who fixed it has his own service shop at his home thus no overhead. Dealers are $ 86.00 hr around here too.

 

isnt oil in some of the plug holes normal in such an engine design-- especially after 113k?

at about 101,000 I replaced my spark plugs. I found oil build up in a few of the oil plug holes- I changed the plug- and now im at 154,000.

still running factory coils and boots etc.
I would just check every 10K or 20K miles to see how much oil is seeping past the seals.

 

I wouldnt think it was normal to have oil puddling up around the plugs deep in these holes since our gasket/seals are leaking. We measured the the seals old vs new with a micrometer & they were compressed .030". Our Tblazer had a miss in the engine too & new plugs, seals, boots, fixed it. Guess your lucky @ 154,000 miles. At least you know what it will cost when you do have to repair these leaky seals in the future though. Hope you dont have to fool with it though as this engine is poorly design. I kinda inherited this vehicle thry the woman as her exhusband bought it. I wont be buy us another one I can tell you.

 

well I'm glad you explained the design and steps to renew plugs, Thanks Unfortunately for me, I asked the seller/tech when he had changed plugs & at 140k he says
"I haven't" excuse me? This explains it....

 

replacing the plugs in an inline 6- is quite easy.

 

In other words, he has no insurance, not collecting taxes, has no business license and is not paying income taxes!!! Sounds like an honest guy that YOU can trust. My shop rate is $95 per hour. I pay taxes, utilities, insurance, collect taxes to better my community, (maybe), I file income taxes every year, I have the latest diagnostic equipment and information system and am always slammed with work. How about you give me his name and address so I can contact him????

 

I replaced my spark plugs a couple weeks ago and noticed oil on them and someone told me to replace valve cover gasket and intake so I did. Now it's misfiring any idea what it could be?

 

when you replaced the intake manifold gasket; did you remove the injectors from the manifold?