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2005 chevy trailblazer_ls_ext
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Discussion Starter · #1 ·
Hi all. Simply looking for advice here..

Have a 05 TB, 4.2L IV6, 70K miles. Runs OK except at idle (esp when slowing down like coming to a stoplight), then it runs rough, RPM gauge bounces 200-400 RPM, and will stall from time to time.

Took to dealer, checked compression, #3 cylinder reading 130, others are 180. (Check engine light on, code reads cylinder 3 misfire). Dealer recommending taking head and replacing it - somewhere around $3500. (Had already replaced plugs recently, checked for vacuum leak, and tried new fuel injector all immediately prior to this).

Called GM looking for possibility of after warranty assistance, they won't do anything until they have the *exact* problem. Of course, that means I have to authorize them to pull the head -- which means paying for 20 hrs labor, without knowing if they will do anything or not.

Am I being unreasonable to think this happening at 70K miles is unusual and hoping for GM to assist in some way?

Any advice welcome, thanks.
 

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Welcome, and horribly sorry about the situation....

You're on the early part of the bell-shaped curve for sure, but cyl 3 compression problems have been showing up in reports here for a couple of years, IIRC. GM never seems to help. Only extended warranty folks have been coming out of the process cheaply.

The idle problem may also be a dirty throttle body, but if you're getting cyl 3 misfires, that's a worse issue that may end up damaging your cat if not fixed.

Certainly the dealer isn't the cheapest place to get it fixed. Ebay has rebuilt heads for $600. http://car-part.com/ is a portal to all sorts of auto recyclers, and I see one listed as LIKE NEW/ /MACHINE SHOP SERVICED from a 2004 in Fayetteville for $350.

Do you have a trusted independent mechanic to do the work? Can you get recommendations? It's still lots of labor to change a head, but you can get out of this for a lot less than $3500. It's just that GM (the new GM) can't give too much money away, even if it's a common problem. If it was going to cause a wheel to fall off and cause a roll-over, then the NHTSA might get involved. Not so much on low compression issues.

Anybody else with a compression repair story to chime in?
 

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Low compression will result in some uneven idle and eventually a non-ignition miss, but shouldn't set a code for a mis-fire. Try swapping the coil on cylinder 3 with another and see if the mis-fire changes.....you didn't mention replacing or swapping the coils. - My bet is you have a bad coil pack causing the misfire.

You'll still have the cylinder 3 low compression, but at least it will be relatively safe to run. Then the issue will be what to do to fix cylinder #3....but this will buy you some time. If all else, you could fix the mis-fire and trade for another, maybe a Denali, an SS or a newer TB with more features. (Just a thought).
 

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Discussion Starter · #4 ·
Thanks for the responses. I had this same rough idle problem last summer and wasn't really able to diagnose/kill it then (then summer ended and it "seems" to be more a hot weather thing, doesn't seem to have with the same level of annoyance during the winter). Last summer the coil packs were eliminated, to be fair that doesn't mean they aren't part of the problem *today* though.

I guess part of the reason I got my hopes up about GM maybe helping was a post I found on another forum. It referenced PIP4013B, which was titled as "P0300 DTC and Engine Misfire at Idle - Possible Leaking Intake Valves - keywords CEL compression controls excessive high leakage leakdown low MIL miss - (Mar 28, 2008)". That P0300 is the error code I've got. The reply posted mentioned "The factory is aware of a condition that causes this premature wear and has issued a PI or Preliminary Investigation into this subject" and the PI listed 2002-2006 TBs.

I do have a trusted mechanic (albeit not local, but within reach), so I have that option as a fallback. His initial thought was to pull the head and send it to the machine shop. I guess I'm a little nervous about that -- mainly from my ignorance of how that works and my lack of mechanic skills, not from any "real" reason :)
 

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There is nothing wrong with getting your current head reworked at the machine shop. I've had three done in my lifetime, although not to the Roadiemobile yet. It's done all the time with great success. Using new parts is just the dealer's way to stick GM with the warranty bill in case the new head assembly is bad. Otherwise the rework process would be dependent on their technician's skill, which varies all over the map.

An independent mechanic lives and dies by their reputation, so incompetent ones seem to shuffle off and migrate to Interstate exit ramps where they can prey on transients with no need for repeat business. :hissy:
 

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The reason for a compression leak, is usually a pretty easy thing to find.

Remove plug, replace with a tool that will let you inject compressed air into the cylinder.
The cylinder has to be near top dead centre, or a little past, to ensure the valves are in a closed position.
Turn on the air. The air will find the leak and you check where the air is coming out of the engine.
Tail pipe = exhaust valve
Throttle body = intake valve
Radiator = head gasket
Fill pipe = rings

But, your only down 50 lbs. That won't cause an idle problem or toss a code.

I'd do as ylab suggests, work on the #3 coil.

Fix the coil and clean the throttle body and the rough idle and CEL will go away. Then toss in an injector cleaner and a valve cleaner (into gas tank).
 

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Head job considerations..

Not suggesting this is what you have (I hope it isn't), so exhaust the cheap/easy fixes first. But if it seems more and more like a head problem, consider my experience with a weak #3 cylinder in this thread:


http://forums.trailvoy.com/showthread.php?t=59173

Not what you want to hear, but at least you'll be a little more informed, should it go that route. Take note of the broken head bolts if you decide to pull the head. It's unavoidable. I was told that here by dealer mechanics and it proved true.
 

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Well, add me to the growing list of those affected by low compression in cylinder #3. In October 2009, only about 55K miles on my 2004 4.2L I6 Envoy, I started experiencing ocassionaly stalling and a rough idle. After trying just about every quick fix it might be (plugs, coils, O2 sensor, fuel system treatment, etc) I broke down and took it into a trusted, local mechanic.

A compression tested revealed all cylinders at around 185#, with the exception being #3, which was ~50# low. So, the head came off...and yes, three bolts broke off in the block during removal.

We've since learnt that one of the #3 exhaust valves was just *starting* to leak by....enough to cause the rough idle although oddly enough the truck felt smooth as silk at highway speeds.

I'm now in the early stages of working with the aftermark warranty company that is to service the extended warranty contract I accepted at time of purchase. The plan is a full valve job.

I'll update this thread as I learn more...
 

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I am going through this as well with my 05 Envoy with fairly low mileage. I planned to post my story when it was done, but I'll share the experience now as it might help you. My cylinder 6 compression is low at about 110, all others at 180. I have the typical rough idle, but it is smooth during cruise. Gas mileage has been getting poorer as time goes on with this problem. I called GMC customer assistance asking for help since I am out of the 3yr/36K warranty with about 65K on the truck. I had already performed the test with a friend, but needed a GM dealer to confirm. I took it in, and they confirmed the low compression. Like has been said on these posts before, GM and the dealer want the head to come off at your risk to confirm it is not a user induced issue ($540). Since I was certain it was a valve problem, I had them do it. As soon as they found the bad valves, GM agreed to a 50-50 cost sharing on the repair. They are sending it out to replace the 2 leaking exhaust valves and machine the head. Total cost of the job is about $2000. I'll pay $1000 out of pocket. They are working it this week. Hope this helps.
 

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byrnejj - 50/50 is BS, and you know it. Your vehicle is a model year '05 with 65K miles and you think it's appropriate for GM to charge you $1,000 for a defect in their product?

As long as I'm posting, please allow me to update you on my experience thus far. Like I posted earlier, I already had confirmation that one of the intake valves on my #3 cylinder was the problem. No need to tear into the engine either. A simple compression test confirmed the problem was compression and not spark or fuel and a follow-on leakdown test was used to isolate the fault to the intake side (versus exhaust or rings). Any competent mechanic worth their salt can do this in less than an hour. Once you know this you can be confident in your approach. They have to confirm it? Sure, go for it. It is what it is and GM will eventually come to same conclusion as you regardless of what they say to you.

When I confronted one of my local Chevy dealers with what I knew I asked that GM step in and correct the issues, especially knowing what I knew about similiar issues with the same engine. In fact, when I was sitting in the service manager's office he told me they had 2 other vehicles (one an '03 Trailblazer and one and '04) with the same exact issue. The only difference being either the cylinder affected or the mileage on the vehicle (one was quite low, as was mine, and the other was higher at about 100K).

Now you tell me. Three vehicles at the same dealership with the same problem....hmmm. GM full well knows this is a BIG problem as so far they've refused to step up the plate and take care of this like they should. There's already been a bulletin released on the I5 with the same failures types. I can only assume they just haven't been pushed far enough to do the same with the Vortec 4200 I6. But you and I (and anyone else reading this) knows damn well they should. Their plan, as far as I can tell? Sweep it under the rug and hope nobody notices (including the NTSHA).

The figure I was quoted on the repair, per GM's standard method - replace the head - was ~$4,000. I can't explain the disparity between the cost you've been told and the cost I've been quoted. But I can tell you this, I sure as hell didn't accept a BS 50/50 offer. Nope. GM will be picking this up. Period. Ask them what they think about a BBB case and see if that changes things. And if you need my help, I can provide you with copies of any documentation I have regarding the arrangements of the repair. And for the record, my Envoy only has a few thousand miles less than yours. So our situations are very comparable.

So, you can let GM rape you. Or you can demand satisfaction. It's your money and your choice. Me? I took a stand and everyone involved knows GM is clearly at fault.
 

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Also - for complete, public documentation purposes machining the head would NOT have fixed the problem in my case. The intake valves seats for the #3 cylinder were really soft which was confirmed when my mechanic attempted to lap them down (just to confirm what we already knew).

So the only choice is the REPLACE the head. If you attempt to "fix" the head with a valve job you're all but guaranteed to repeat the same repair down the line.

Beware of any GM dealer that tries to rework the faulty head. As you can see here GM's repair procedure calls for REPLACEMENT.

Make sure you ask your dealer why they aren't following procedure if they try to cheap out and machine the head.

#PIP4013B: P0300 DTC and Engine Misfire at Idle - Possible Leaking Intake Valves - keywords CEL compression controls excessive high leakage leakdown low MIL miss - (Mar 28, 2008)

Subject: P0300 DTC and Engine Misfire at Idle - Possible Leaking Intake Valves


Models:

2004 - 2006 Buick Rainier
2002 - 2006 Chevrolet Trail Blazer
2002 - 2006 GMC Envoy
2002 - 2004 Oldsmobile Bravada
2005 - 2006 Saab 97x
with 4.2L Engine (VIN S - RPO LL8)

This PI was superceded to strictly reference the cylinder head replacement procedure outlined in 07-06-01-018, remove old information that conflicted with the information found in 07-06-01-018, and add an important notice to prevent valve damage. Please discard PIP4013A.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.


Condition/Concern:

On rare occasions, a SES light and P0300 DTC may be encountered as a result of single cylinder misfires only at idle. These misfires may or may not be felt and they will disappear off of idle. If the engine misfires do not occur at idle, this PI does not apply. Author's note: Rare, my ass.


Recommendation/Instructions:

If the SI diagnostics do not isolate a cause for this concern, perform a cylinder leakage test as outlined in the "Cylinder Leakage Test" procedure in SI and document all leakage rates on the repair order. When performing the cylinder leakage test, it is very important to hold the crankshaft with the related piston at top dead center to ensure that the valves are fully closed or inaccurate results may be obtained. If an aftermarket leakdown tester is used, the instructions of the aftermarket tester should also be referenced because with some aftermarket testers, it may be necessary to limit the air pressure to 50 PSI in order to obtain accurate test results.

If a leaking intake valve is found, replace the cylinder head and valves by following the latest version of 07-06-01-018.

Important: Before replacing the cylinder head, review the latest version of PIP3940, which contains some tips for using the lower timing gear tensioner holding tool (EN48464) described in the latest version of 07-06-01-018. This bulletin contains a revised cylinder head replacement procedure that no longer requires removal of the oil pan, front cover, water pump, or crankshaft dampener. Also, as mentioned in 07-06-01-018, it is important to install the cylinder head before you install the camshafts. Once the head is installed, the J44221 (Camshaft Holding Tool) should be used to hold the cam flats as the camshafts are installed with the #1 piston at top dead center. If the cylinder head is installed with the camshafts in place, without using the J44221 to hold the cam flats, or without the #1 piston at TDC, one of the valves could bend, resulting in an engine misfire at idle once the repairs are complete. As a result, it may appear that the new head has the same concern as the cylinder head that you just replaced, when it is actually the result of a bent valve.
 

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Same Issue on 2004 TB with 102K

I have the same problem. Engine misfire and idling rough. SES light comes on intermittently. Did not always feel the rough idle.

Took it to the dealer and 50psi compression on cylinder #3. They followed the procedure in the above service bulletin and came to the conclusion that it needed a new cylinder head. I can get the parts myself for a discount since I am a GM employee, but they quoted me $950 for labor to put it in.

I looked at another service bulletin and found something that said that the I6 engine may have sticking valves resulting in rough idle, a P0300 DTC code, and low or no compression on 1 or multiple cylinders. It recommends using fuel injector cleaner "GM Fuel System Treatment PLUS" part number 88861011 or ACDelco 88861013. Then it recomends using "GM Top Engine Cleaner" part number 12345089 and follow the instructions on the can. This is supposed to clean the valves and possibly eliminate the sticking.

I am going to try this first, and if that doesn't work...guess I'll be replacing the head...
 

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I just bought a 2008 Trailblazer LT with 83,000 miles. The truck was very clean and well taken care of. After owning it for two days the SES light went on. I had the truck checked at my local dealer. Cyl 2 had a misfire. We replaced the coil and plug. The light went out for two days then back it came. Code p0300/01. The dealer said it was under factory warentee. They thought it was the fuel injector. But it was low compression in the cyl. The truck has been at the dealer almost a month. I have made two payments and have driven it 8 times. The fix was to resleave the block and rering the piston. I fought with the service manager and they are going to replace the engine.
 

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2005 I6 Compression Issues

All:

I'm new to the forum and have found the information here very useful. I have a compression issue on my '05 Trailblazer similar to those mentioned by others (my issue is with the 5th cylinder). Getting 30 psig out of number 5 and about 140 psig out of the rest. I'm looking to perform a pressure test to better isolate the leak, but fear a head replacement is in my future. The car has only 93K miles and I have no extended warranty.

I'm really concerned with breaking head bolts as mentioned in previous postings. Any tips on how to avoid this issue?

Also, can anyone confirm that I won't need to take off the oil pan, front cover, water pump or engine pulley as posted by freecableguy? I have the valve cover already off and everything is moving as it should, but i suspect there is a leak out of one of the exhaust valves.

Thanks for all your help,
Bill (Yesman85)
 

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Hi Bill, sorry to hear of your situation but you've come to the right place. More likely then not, your head will have to come off and either be replaced or get machined. I had to have my '06 done at only 76,000 miles for a misfire on cyl 1. The machinist said he was surprised I didn't have more cylinders misfiring because a number of valves were ovaled. Anyway, you can do the job without having to remove the oil pan and front cover ect., but it requires a handful of specialty tools. Someone suggested this to me and I will suggest the same to you. Get a subscription to alldatadiy.com It costs about $30 for 1 year and has all of the factory service manuals, wiring diagrams, parts info and more. What it also has, and which is what you need most, is the technical service bulletins. There are tsb's for removing and installing the head without having to remove all those other parts and it details the specialty tools you'll need including the part numbers and how to use them. It's invaluable because if you have to remove the oil pan and all the other stuff, the labor is doubled and the headaches will be quadrupled.

I did the job myself a few months ago and spent just under a grand on the parts, the tools and the machine shop. I sold all of the tools on eBay afterward and was able to recover some of what I spent.

If you take your time and label all the parts and connectors and perform the job systematically, it isn't too daunting afterall. Breaking head bolts seems to be unavoidable, I was a lucky one and only broke one bolt, but they aren't too difficult to remove with the right tools. If you decide to take on the job yourself, I can give you a ton of advice. Feel free to ask. Best of luck.
 

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jpoogie84:

Thanks for the info - really appreciate your help. I'm going to try the repair myself. I'd like to ask a few more questions:
1. Did you disconnect the AC line that runs across the top of the engine or were you able to keep it connected and just work around it?
2. What procedure did you use for removing the cracked head bolt? Did you use a drill extractor set to get the old bolt out?
3. Could I get the service bulletin from the dealership? (I'm thinking this would be fair compensation for selling me a piece of junk that I had to have hauled 800 miles when it broke down on vacation.)
4. Did you pressurize the cylinder through the spark plug hole to verify the valve was the problem and not a piston ring?
5. Any other major watch-out? I still need to disconnect the exhaust manifold and still can't get the intake out of the engine compartment (although all the bolts and hoses are disconnected).
6. Approximately how much did you play for the specialized tools?

We've already bought a replacement car, so I'm not under crunch timing on this repair. I'll keep you posted on my progress. Thanks again for all your help.
 

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jpoogie84:

Thanks for the info - really appreciate your help. I'm going to try the repair myself. I'd like to ask a few more questions:
1. Did you disconnect the AC line that runs across the top of the engine or were you able to keep it connected and just work around it?
2. What procedure did you use for removing the cracked head bolt? Did you use a drill extractor set to get the old bolt out?
3. Could I get the service bulletin from the dealership? (I'm thinking this would be fair compensation for selling me a piece of junk that I had to have hauled 800 miles when it broke down on vacation.)
4. Did you pressurize the cylinder through the spark plug hole to verify the valve was the problem and not a piston ring?
5. Any other major watch-out? I still need to disconnect the exhaust manifold and still can't get the intake out of the engine compartment (although all the bolts and hoses are disconnected).
6. Approximately how much did you play for the specialized tools?

We've already bought a replacement car, so I'm not under crunch timing on this repair. I'll keep you posted on my progress. Thanks again for all your help.
I'll go in order here.
I didn't have to disconnect the a/c line but what I did was remove the bolts that support it and then I zip-tied it to the hood latch mechanism. It was out of the way enough to where it didn't cause any trouble. You'll see where the bolts are that need to come out so there is no need to have the system evacuated.

These head bolts are called Torque To Yield bolts which, if my understanding is correct, they are torqued to just below their breaking point making them very susceptible to snapping during removal . The service manual tells you to wrap the head of each bolt a few times with a punch and a hammer and that should shock them enough to where they shouldn't break. People's results seem to vary. I smacked the hell out of every bolt and as I said before, only one broke. I think the key to removing them without breaking is using slow constant force on a very long breaker bar as opposed to short jerky jabs. The bolt that broke was the very first one I removed, which scared the bejesus out of me, but all I was using was an 18" breaker bar. I put a long pipe on the end of it and went real slow and had no problems with the rest. They make a broken bolt extractor kit specifically for the head bolts of our 4.2's as well as a few other engines in the same family but it comes with a bunch of things that you won't need. If you are careful and have a steady hand with a drill, I wouldn't bother investing in the kit. A 5/32 left hand drill bit and a #3 ez-out is really all you need. You can get both of those from Grainger for a couple of bucks. The kit the service manual calls for is around $325 I believe.

I can only imagine what it might cost to be towed 800 miles. Yikes! Is there such a thing as AAA Diamond? Haha. I honestly don't know if the dealer would give you the service bulletin or not but, with a job this large, you really do need access to all the service manuals which is why I'd go with the alldatadiy.com subscription. There are a whole bunch of torque values and procedures you'll need that aren't covered in the tsb.

I never actually did a leak down test because my situation was kind of different. I was getting a cylinder 1 misfire every once in a while and then more and more frequently. I pulled my hair out for weeks trying to figure out the problem. I started swapping coils and spark plugs to no avail and then I did a static compression test. That's where you screw a pressure gauge into the spark plug hole and then crank the engine for a few seconds. The strange thing is that all 6 cylinders had excellent compression. If memory serves me right, they were all around 215 psi with the lowest one around 205psi. A negligible difference. That being the case, I thought it ruled out a valve problem and so I started looking other places. I replaced the fuel injector, no help. Swapped the injector with a known good one, no help. Checked every wire end to end from the PCM to each injector and coil, couldn't find anything wrong. Seafoamed the engine, replaced intake manifold gaskets.....the list goes on and nothing fixed it. That was the point I threw in the towel and took it to my local thieving bastard dealership to have them diagnose it. I was expecting for them to tell me my PCM was at fault but no, not so lucky. They of course said it was my head and I had valve issues. When I asked how can it have such excellent compression and still have valve issues, he gave me some bs response but alas, he was right. So getting back to the real question on hand, in your situation, you should probably do a leak down test to 100% confirm it is the valves and not a head gasket or piston rings, ect. With the history of these engines though, more likely then not, you will need a valve job.

The best advice I can give for removing and installing the head is to read the procedure over and over until you have a thorough understanding on how to use all the tools and what it is you need to do. The timing chain can be a little tricky if you aren't careful, and things can go south real quick. They nearly did for me but luckily I was able to unscrew my screw up and it all worked out.

You should only have to remove the exhaust manifold from the head and not from the bottom end. I left it attached so it stayed in the engine compartment. The intake manifold is a bit of a pain. Just make sure you remove all 10 bolts as some of them are kind of hidden and also remove the throttle body. I don't think it will come out with that still attached.

I spent about $300 on all the tools but if you are lucky, someone will be selling them on ebay and you can get a bargain.

Best of luck, Ken
 

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Ken:

Thanks - your experience with this issue is really helpful. I plan to take your advice and alldatadiy subscription. It may be a week or so before I can round up all the tools, but I'll keep you posted on my progress.

On a personal note, I've been a die hard Chevy guy my entire life (heck - I even won a Chevy during the Hot Button contest of several years ago), but the experience with this car and all the problems we're had has really turned me off of Chevy. It really is disappointing to think that you can't even get 100,000 miles out of a car without major issues. When the dealership in Florida said they wanted $8,000 to replace the entire engine - I nearly had a stroke! !

Anyway, enough negativity. Thanks for your advice (and the help of my Uncle), I'm confident I can get this thing back on the road. Thanks for all your help.

Bill
 

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Cyclinder Head Removal

Gang:

I'm right in the middle of removing the head from my 05 Trailblazer with the 4.2L engine because of a bad exhaust valve on the 5th cyclinder. I'm following service bulletin 07-06-01-018A and have everything taken off (exhaust and intake, valve cover, etc) and I'm to the point of loosening the spocket bolts on the exhaust and intake camshafts. I can't get either bold to loosen (I am holding the camshaft from turning during this process). I'm reluctant to add more force for fear of damaging the bolts. Any pointers? Also, am I correct in assuming there are NOT left handed threads on these bolts? Any help is appreciated.

Thanks,
Bill
 
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