May buy 06 H3 143K miles $7400, head question.
Senior Member
Joined: Jul 2012
Posts: 9,016
From: C-Town
Hummerz, today when I got home from work (22 mile drive in half stop and go and half 60mph Highway) I say in the driveway for 10 minutes in Park with the engine running. No light yet.
I do note that when in gear and stopped at a light, there is a slight roughness to the idle. There is no flutter or fluctuation in the idle speed once it settles. This may be a normal feel as I've never had a non V-8 V-6 engine prior to this I-5.
When coming to a stop, like at a stop sign in town when your going block to block and stopping, you notice that at the instant just before you cease movement, the RPMs dip a bit lower (450-500) than idle (600 or so) and there is a shudder in the engine before the engine raises back to a steady 600 or so (indicated on the gage) and remains constant but with that mentioned slight stutter/roughness that is felt while in gear and stopped.
Also observed is that song in the driveway running in Park, the idle is smooth and does not flutter, fluctuate or have any roughness.
I may have gotten a freak engine code, and I may be comparing the feel of an I-5 to my experiences with V-6 and V-8 engines. So it is entirely possible that I'm over reacting.
I do note that when in gear and stopped at a light, there is a slight roughness to the idle. There is no flutter or fluctuation in the idle speed once it settles. This may be a normal feel as I've never had a non V-8 V-6 engine prior to this I-5.
When coming to a stop, like at a stop sign in town when your going block to block and stopping, you notice that at the instant just before you cease movement, the RPMs dip a bit lower (450-500) than idle (600 or so) and there is a shudder in the engine before the engine raises back to a steady 600 or so (indicated on the gage) and remains constant but with that mentioned slight stutter/roughness that is felt while in gear and stopped.
Also observed is that song in the driveway running in Park, the idle is smooth and does not flutter, fluctuate or have any roughness.
I may have gotten a freak engine code, and I may be comparing the feel of an I-5 to my experiences with V-6 and V-8 engines. So it is entirely possible that I'm over reacting.
Autel Maxiscan MS300 OBDII OBD2 Car Auto Diagnostic Code Reader Scan Tool Can | eBay
The reason to have this handy tool, you can scan yourself many times under different driving cycles to further pinpoint the reason for the code.
In the meantime you can go to your local auto parts store or auto repair to get your computer scanned for free.
Why do I state this, chances are there is a new entry p0300, however only a "soft" code entry(only "hard" codes activate the cel).
Advise after you get the computer scanned.
Senior Member
Joined: Jul 2012
Posts: 9,016
From: C-Town
If you checked for codes and none found, check the fuel trims.
Super Moderator
Joined: Jul 2007
Posts: 13,101
From: Boat Town USA MI
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I do note that when in gear and stopped at a light, there is a slight roughness to the idle. There is no flutter or fluctuation in the idle speed once it settles. This may be a normal feel as I've never had a non V-8 V-6 engine prior to this I-5.
When coming to a stop, like at a stop sign in town when your going block to block and stopping, you notice that at the instant just before you cease movement, the RPMs dip a bit lower (450-500) than idle (600 or so) and there is a shudder in the engine before the engine raises back to a steady 600 or so (indicated on the gage) and remains constant but with that mentioned slight stutter/roughness that is felt while in gear and stopped.
I may have gotten a freak engine code, and I may be comparing the feel of an I-5 to my experiences with V-6 and V-8 engines. So it is entirely possible that I'm over reacting.
I do note that when in gear and stopped at a light, there is a slight roughness to the idle. There is no flutter or fluctuation in the idle speed once it settles. This may be a normal feel as I've never had a non V-8 V-6 engine prior to this I-5.
When coming to a stop, like at a stop sign in town when your going block to block and stopping, you notice that at the instant just before you cease movement, the RPMs dip a bit lower (450-500) than idle (600 or so) and there is a shudder in the engine before the engine raises back to a steady 600 or so (indicated on the gage) and remains constant but with that mentioned slight stutter/roughness that is felt while in gear and stopped.
I may have gotten a freak engine code, and I may be comparing the feel of an I-5 to my experiences with V-6 and V-8 engines. So it is entirely possible that I'm over reacting.
As with all GM fuel injected vehicles, you need to clean the Throttle Body every 30-60K miles (this stuff is not in the owner's manual, they want people to freak and bring it to the dealer for $$). Use Throttle Body cleaner, follow the instructions and/or search out the many Throttle Body cleaning threads here.
A dirty TB causes a RPM inconsistency (the fly by wire can't smoothly move the butterfly to control the idle to where the PCM is telling it to be upon stopping/starting so it over-reacts a bit) near idle. Lots of people come on here an say, my truck almost stalls when I stop and I think it is going to die. It is called a false stall = dirty TB.
While you are doing the TB clean, might as well clean the MAF, using .... MAF cleaner. Threads on that as well.
Junior Member
Joined: Mar 2014
Posts: 25
From: Pennsylvania (Temporarily)
I had a 2007 (early model in that year) with a 3.7 liter. The same code P0300 came up and GM replace the head under warranty. Common issue on 2006 and early 2007's. Even with different engine. Had a wiper motor issue where they stick in the middle of the windshield, changed the motor twice, easy fix, worked great after that. One thing to think about, I noticed you said the 4x4 may not be working, I had the shift fork melt in my transfer case. That was a polyurethane fork in 2006 and 2007 and they then upgraded H3's to an aluminum fork. They put a new one in mine and it worked great. They like go through axle seals and those HVAC lights will go out. Have to solder new ones in, no light bulbs. Another thing, these H3
s have a potential for cracked radiators near the top by the fan shroud. The shroud bumps into the radiator and can cause it to crack. Mine had hairline cracks and I replaced it. Also the transmission cooler is built into the radiator on the bottom. They can sometimes crack and mix the fluids and mess up your transmission. These are just some things that can happen to anybody, but they are some bugs that were slowly worked out as the years went on. The steering column can clunk around, but an intermediate shaft (shaft that goes through firewall) can become sloppy. I never replaced it and GM just packs grease in there and doesn't really fix it. I had about every problem with mine that you could have. Despite all these things, I loved my H3. I traded it in on March 1st on a 2006 H2. If you love it, you will deal with it or can use it as a project and work on things over time. Just passing along some info. Have fun with it and good luck :}
s have a potential for cracked radiators near the top by the fan shroud. The shroud bumps into the radiator and can cause it to crack. Mine had hairline cracks and I replaced it. Also the transmission cooler is built into the radiator on the bottom. They can sometimes crack and mix the fluids and mess up your transmission. These are just some things that can happen to anybody, but they are some bugs that were slowly worked out as the years went on. The steering column can clunk around, but an intermediate shaft (shaft that goes through firewall) can become sloppy. I never replaced it and GM just packs grease in there and doesn't really fix it. I had about every problem with mine that you could have. Despite all these things, I loved my H3. I traded it in on March 1st on a 2006 H2. If you love it, you will deal with it or can use it as a project and work on things over time. Just passing along some info. Have fun with it and good luck :}
Super Moderator
Joined: Jul 2007
Posts: 13,101
From: Boat Town USA MI
I had a 2007 (early model in that year) with a 3.7 liter. The same code P0300 came up and GM replace the head under warranty. Common issue on 2006 and early 2007's. Even with different engine.
One thing to think about, I noticed you said the 4x4 may not be working, I had the shift fork melt in my transfer case. That was a polyurethane fork in 2006 and 2007 and they then upgraded H3's to an aluminum fork. They put a new one in mine and it worked great. }
One thing to think about, I noticed you said the 4x4 may not be working, I had the shift fork melt in my transfer case. That was a polyurethane fork in 2006 and 2007 and they then upgraded H3's to an aluminum fork. They put a new one in mine and it worked great. }
This misunderstanding is what has people assume there is a "common head" problem with the I5s, just ain't so. Then these forum chats, where people read about one instance and assume it universally applies to all, perpetuates the basic misunderstanding.
The OP also stated in another thread that he figured out his 4X4 was fine.
Last edited by Doc Olds; Mar 21, 2014 at 10:18 AM.
Senior Member
Joined: Jul 2012
Posts: 9,016
From: C-Town
Thank you for your comment, but I have to say you have have a misunderstanding. ONLY the 3.5L (2006) had the head with the non-hardened valve seats. Yes the schmucks at the GM dealer replaced heads on 3.7Ls, but not because it was a common issue, but in most instances because of incompetence, fear and/or paranoia, and a fat warranty program that had low confidence in the dealership network. The dealer could make $$ claiming the head was bad, even though it was completely reparable, and GM let them do it because it actually takes a degree of skill to diagnose the valvetrain issue and fix it right the first time. Today's techs put far too much weight on a piddly computer code than mechanical knowledge, you still have to use your brain to fix what's wrong. Not trying to suggest that there would never be a circumstance where a 3.7L head would need to be replaces. Regardless, whatever the reason for replacing a 3.7L head, it would not be a common issue with the 3.5L head defect.
This misunderstanding is what has people assume there is a "common head" problem with the I5s, just ain't so. Then these forum chats, where people read about one instance and assume it universally applies to all, perpetuates the basic misunderstanding.
The OP also stated in another thread that he figured out his 4X4 was fine.
This misunderstanding is what has people assume there is a "common head" problem with the I5s, just ain't so. Then these forum chats, where people read about one instance and assume it universally applies to all, perpetuates the basic misunderstanding.
The OP also stated in another thread that he figured out his 4X4 was fine.
Well said!
4x4 works fine, I was not used to this new fangled technology and I thought I had a problem until I took it to my father in laws farm and played on an embankment. She works fine!
It's been 5 days and 300 miles and that code still isn't back. I tried letting it sit in the driveway to idle for 12 minutes to try to get it to trip the code and got nothing. For now I'm going to ignore that until it comes back. I did run a full tank of Sunoco Ultimate with Lucas injector cleaner since the light came on, so maybe that cured it?
Today I stopped and got CRC throttle body cleaner and CRC air sensor cleaner. Doing the cleansing on those two items is on my weekend chore list. I have another issue that I'll start a new thread on.
It's been 5 days and 300 miles and that code still isn't back. I tried letting it sit in the driveway to idle for 12 minutes to try to get it to trip the code and got nothing. For now I'm going to ignore that until it comes back. I did run a full tank of Sunoco Ultimate with Lucas injector cleaner since the light came on, so maybe that cured it?
Today I stopped and got CRC throttle body cleaner and CRC air sensor cleaner. Doing the cleansing on those two items is on my weekend chore list. I have another issue that I'll start a new thread on.
