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2004 chevy trailblazer_ls_ext
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Discussion Starter · #1 ·
I posted some time back seeking help with a rough idle and I just want to pass on the things learned through the long and painful experience.

I had gotten intermittent codes (forgot the #'s) for too rich, too lean and once got a code for a misfire on cyl 3. The vehicle ran fine on the road, and just above idle for that matter, but shook at idle and you could smell the exhaust was a bit rich. Also, the cruise control would sometimes not activate. (some symptoms were discovered later in the process)

The first thing I tried was cleaning the throttle body that is discussed extensively here. My TB wasn't very dirty after 94,000 miles. I was a bit puzzled by that after seeing others pictures that were much dirtier at much lower mileage. In any case, that didn't help at all.

The next thing I tried was replacing the plugs with Delco replacements - no change.

The next thing I tried was replacing the front O2 sensor with a Delco replacement - still no change.

The next thing I tried was checking the compression. I had read here of several head problems that were discovered by finding weak compressions. So I put the gauge on it. I had 200psi on every cylinder except for #3, which had 115psi. I put a little oil on the cylinder, but I still got 115psi, so it seemed that it was indeed in the head.

I consulted here with others who experienced head problems and most found that replacing/repairing the head ran between $3000-$4000 at the dealer. Since I had already had bad experiences with my dealer on much simpler issues, I decided to try an independant mechanic a couple friends had recommended. Some here suggested trying it myself in the driveway, while others who were experienced with this job, said that would be insane. As it turns out, it would have been.

The head weighs 94 pounds. I know that because I got a price on a re-manned one and had them weigh it for shipping. It would be very difficult to handle an awkward 94 lbs. leaning over your engine. A lift is necessary. Another caution I was given, was that it is a certainty, that some of the head bolts are going to break in the block. The first day the mechanic started working on it, he called me and told me that 5 bolts, had indeed broke. He seemed surprised I wasn't upset. But this forum had already prophesied this would happen, so I expected it and it doesn't seem avoidable. Since some of these were under the dash, due to the length of the I6 head, the engine had to come out. It would not be worth it to risk ruining the block trying to do it in place. Prior to this development, my bill was estimated at around $1000. Now it was on the way up. Once the head was off, the mechanic said you could see daylight between the #3 exhaust valve and it's seat. That was definitly the source of the low compression and rough idle.

5 full weeks later, I finally have the TB back. Between the mechanic and the machine shop and the wait for parts, it didn't seem like I would ever get it back. In the end, the bill ran $1745.64, after taxes-$1894.02.

During the course, many asked, "why not just replace the engine?" If you determine you have a head problem like this, that may in fact be the best answer if you choose that route up front. Once you're started though, changing course results in throwing away the labor cost you've already incurred pulling the head, so really think about it before you start. Knowing I had excellent compression except from the #3 and knowing my engine was cared for and oil was always changed on time, I pushed on and I'm confident that was the right thing to do, at that point. After all, I was already liable for the head removal.

I would advise if you start down the road I chose, ask the mechanic up front if he is ready to deal with all I have described above. Some may not even have the ability or the nerve to deal with all of that (or you may not have that kind of faith in them). Keep in mind that when I started, I was expecting to spend around $1000. Complete engines are available online, such as on Ebay for less than that, some with warranty, then you just have to pay labor to do the switch. Still, you have to wonder whether the engine was cared for as you know your own was, and also, will it too have a bad head eventually? From what I've read on here, it's not exactly an isolated issue.

After all was said and done, my TB runs smooth as silk, and I hope that continues for a long time. In five years and with 94,000 miles, I have probably spent $5000 in repairs to keep this thing on the road.

I must give many thanks to you folks that helped me through this, Roadie, May03LT, Super88, 91RS, and even others who I didn't quite agree with, or got tips from in other threads.

Below is the cost break down and pictures of the valve.

2 Head bolt sets 159.88
1 oil filter 9.10
1 headgasket set 251.36
1 Machine Shop 150.00 (polish, reseat all valves, replace 1)
6 qts oil 21.84 (yes he did short me 1 quart)
1 Dexcool 18.19
1 Gray silicone 7.00
3 cleaner 16.77

17.1 [email protected]$65 1111.50

Total 1745.64
Tax 148.38

Total 1894.02

Here's the valve. See the 3/4 inch section of the seating surface that is black? Yep, that's what costs $2000 to make right.:mad:
 

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2003 gmc envoy_slt
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I'm glad everything worked out for you. Look on the bright side, the dealer would have been at least another $1,000 on the low side if your info was correct.
 

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2002 olds bravada
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wow...sorry to hear that.. this is the first time i've heard an i6 having a burned valve...what causes them anyway?
 

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2003 trailblazer_lt
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Glad to see you got her back! I was this close to pm'ing you about the progress

thanks for taking the time to tell us how you made out!!!



I've done a few head gasket jobs in the drieway but i dont think i would do one of these I6s without a hoist...it looks heavy:ugh:
The head weighs 94 pounds. I know that because I got a price on a re-manned one and had them weigh it for shipping. It would be very difficult to handle an awkward 94 lbs. leaning over your engine. A lift is necessary.
 

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2004 chevy trailblazer_ls_ext
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29 Posts
Discussion Starter · #5 ·
what causes them anyway
I don't really know. The steel itself doesn't look defective. The flat side of the valve, which doesn't need to be precise as the seating surface, isn't machined perfectly. That in itself doesn't matter, but makes me wonder if the seat side was imperfect as well and allowed bypass which eroded that spot over time. Or maybe some debris got caught in there and started the same process.

The valve/stem is dark in color, but is smooth and doesn't look anything like those cruddy valves in fuel additive ads. None of the other valves showed any sign of wear. I'm leaning towards a defectively machined valve.


Anybody know anything factual about top cylinder lubricant products you add to your fuel (Lucas/Marvel etc)? Would that have changed anything?
 

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2004 gmc
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26,181 Posts
Appreciate the detailed followup and analysis. From the mechanic's side, those were 17 HARD hours. Not the easy hours like changing a mode door actuator or a fuel pump. If I was going to be a full-time mechanic I'd like to have a three-tier pricing system, but probably wouldn't be able to get away with it.
 

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2007 buick rainier
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328 Posts
I think I read somewhere that the valves guides were bored at an improper angle. Not sure about that but thought I'd throw it out there.
 

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2004 chevy trailblazer_ls_ext
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Discussion Starter · #8 ·
The used head I priced

Interesting enough, I was told that the re-worked head I priced in Arkansas (94lbs), was removed and re-worked and then the after-market warranty company paid for a new engine to be installed on the claim. Maybe amongst the warranty community, it is deemed more cost effective to do so for that failure.
 

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2004 chevy trailblazer_ls_ext
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Discussion Starter · #10 ·
Springbuck

Not sure. I just assumed a set doesn't include enough to do the whole job. Maybe it was sets for a V-head, which would take two. Or maybe for consistancy's sake, a set is half, whether it is a V-head or I-head. I really don't know.

Maybe he tipped himself:undecided

BTW, I added the recent comment a few posts up (and thus the bump) because I referenced someone to this thread. I have approx 3000 miles since and it's still good.
 

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2002 olds bravada
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314 Posts
Well 17 1/2 hours is a real fast pace !

Pretty fast pace if you could have all the part at hand too .Do think you could ask for a little break on the bolts though .Working on the engine again I just thought about getting the fender sides shock lifters ,that hood latch holder keeps slapping me .
After reading the whole post this should be a alert to switch engines or just go after rebuilt heads. I'd be leaning to go get used engine with warrantee.
Springbuck:coffee:m2:
 

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2004 chevy trailblazer_ls_ext
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Discussion Starter · #12 · (Edited)
Used Engine

I'd be leaning to go get used engine with warrantee.
Yeah, I hear ya. That's why I spelled it out as I did. Doing it again with the knowledge I now have, I probably would too. Also, it may have still come to that if the machine shop determined I needed a new head. That may have been enough to swing it the other way, even after all of the other work.

Broken head bolts/pulling the engine is a foregone conclusion. Are you prepared for the added cost over the original estimate? Is the mechanic capable of dealing with that? Is the mechanic willing to deal with it? Are you confident a valve job is all you need and your head has no other defects that would result in needing a new one? -All factors in deciding.

Most engines on ebay I've seen are under $1000 and many have some type of warranty. Still, I did get 12,000 mile parts and labor warranty from the mechanic I used and I knew my engine was good otherwise. Since it didn't balloon any further, I'm pleased with my choice and the way it has gone so far.


As far as the time - 17.1 hours, I think he uses a the same guide or one very similar to what the dealers use. When he quoted me for the various phases during the process as it changed, it seemed that way. He would tell me up front what the labor was going to be in full and partial hours and stuck to what he told me. Maybe that's why it took 5 weeks. Maybe he had to do easy, more profitable jobs in-between to keep his profit margin at a certain average for the month. I sure was aggravated by how long it took at the time. But looking back, I think he's a pretty good guy.
 

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Discussion Starter · #14 ·
Nope

Obviously, I didn't. I didn't try though. I don't remember anyone else having success with that, so I didn't even entertain it with a 5 year old vehicle with that many miles. I had 9X,XXX miles on mine. With 58,XXX miles, maybe you have a shot.

I now have 133,XXX and no signs of any issue. So if everything else on yours is good, i would say it's worth the repair.
 

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2005 gmc envoy_sle
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I know this is dredging up an old topic... but..

I have the exact same issue with my '05 Envoy. I wonder if I should even bother with trying to remove the head with the engine still in the truck, or if I should just yank the motor complete then try to remove it? I've got the time and room to do either.
 
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