[collyman07]

Just hit 107,000 Been having check engine lights come on for p0300 & p0305 misfire codes. swapped plugs still number five. :anger:

Had a compression check done 55% air intake valve air coming thru intake.

Dealership quoted me 2800 to swap in a new head & then another 1000 to change the timing chain.

I was like whoa i can pretty much buy a whole new engine for that.

Not sure what to do it takes a while for the codes to come on so it must be a slow compression leak...

Anyone with a rebuilt 3.7 head have any problems down the road?

whats the fix for this just new valve seats? i don't want to keep replacing the head

thank you,

 

[FixxxerKH202]

I have 60K miles on a swapped head. Also about 20K miles under boost and no issues.

From what I gather on the little info GM has given the valve seats were machined incorrectly and were damaged by the valves over time. Mine failed at 40K miles.

 

[fitsector]

Looked on all pages of this thread. No affected vins list yet. Anyone has this info. We have an 07,09 ,11,12 Colorados in The family ...

 

[703inthe808]

2007 with 116K. Low compresssion (~80psi) in cylinder #4. Dealer recommended a new engine and quoted me $10,000 which is a f'n crime. Currently looking at other options. Im in Hawaii so finding a decent used engine like winning the lottery.

 

[collyman07]

My misfires went away awhile ago just kept clearing code n not letting the truck idle to long. Not sure what fixed it last thing's i did was a personal leak down test an had the (case relearn) done. Truck healed it self knock on wood.:fart:

 

[joncanyon1]

I have a 2008 Canyon Z71 4x4 Ext Cab 3.7 with 85,000 miles. The heads are at the machine shop as of today for a valve job due to low compression in cylinder #1. If there are any Carmax buyers out there, I can confirm that they will fully cover this without hassle under the Maxcare extended warranty.

It started with a very rough idle when I would WARM start the truck. The RPMs would drop, the truck would shake, then they would spike again. This happened for about 30 seconds. For whatever reason, when the truck was cold (first thing in the morning), it would fire up fine. It progressively got worse so I scoured this forum for some wisdom. I came across the "How To" for cleaning throttle body and changing plugs (Thanks MC). Seemed like a logical place to start. Also cleaned MAF sensor while I was in there. I also searched on YouTube and found a few videos where the oil was said to be the problem (I had my doubts but WTF), so I started changing the oil at 3k vs 5k just to see. That did not solve the problem.

Finally, I brought my truck into the shop, bit the bullet and rented a POS to drive around for a while so they could diagnose. Sure as shit, valve not seating properly and the electrical unit was all jacked so the check engine light never came on. A quick plug into the port revealed the 0300 (I believe) and the problem was found.

$300 deductible and the problem is fixed so I'm not really that pissed off about the whole thing. I hope you have a warranty if this happens to you. For those who think the valve problem is ONLY for the 3.5, I'm sorry to tell you...

 

[Zexy Magician]

I have a 2008 Canyon Z71 4x4 Ext Cab 3.7 with 85,000 miles. The heads are at the machine shop as of today for a valve job due to low compression in cylinder #1. If there are any Carmax buyers out there, I can confirm that they will fully cover this without hassle under the Maxcare extended warranty.

It started with a very rough idle when I would WARM start the truck. The RPMs would drop, the truck would shake, then they would spike again. This happened for about 30 seconds. For whatever reason, when the truck was cold (first thing in the morning), it would fire up fine. It progressively got worse so I scoured this forum for some wisdom. I came across the "How To" for cleaning throttle body and changing plugs (Thanks MC). Seemed like a logical place to start. Also cleaned MAF sensor while I was in there. I also searched on YouTube and found a few videos where the oil was said to be the problem (I had my doubts but WTF), so I started changing the oil at 3k vs 5k just to see. That did not solve the problem.

Finally, I brought my truck into the shop, bit the bullet and rented a POS to drive around for a while so they could diagnose. Sure as shit, valve not seating properly and the electrical unit was all jacked so the check engine light never came on. A quick plug into the port revealed the 0300 (I believe) and the problem was found.

$300 deductible and the problem is fixed so I'm not really that pissed off about the whole thing. I hope you have a warranty if this happens to you. For those who think the valve problem is ONLY for the 3.5, I'm sorry to tell you...

Does your problem sound anything like this one on post 42? Be sure to check out the youtube videos in that post as well.

 

[joncanyon1]

That is it EXACTLY... Its a compression issue in the cylinder. Exact same symptoms for sure. I always use top tier gas

 

[Zexy Magician]

That is it EXACTLY... Its a compression issue in the cylinder. Exact same symptoms for sure. I always use top tier gas

Alrighty... I'll go get it checked!

I've been running top tier for sure. Premium fuel seems to make the issue disappear or at least a whole lot less noticeable (not sure why).

Any idea how much it costs to fix without any extended warranty?

 

[joncanyon1]

I want to say its around $3500... Its pretty much all labor because they have to pull the heads and do a valve job at the machine shop. If the seat is bad, they have to pull it and replace that too. You out of warranty?

 

[Zexy Magician]

I want to say its around $3500... Its pretty much all labor because they have to pull the heads and do a valve job at the machine shop. If the seat is bad, they have to pull it and replace that too. You out of warranty?

I assume so? Bought the truck used @ 60k miles. Has 83k miles now. 2008 3.7L

Not sure if the warranty transfers or if they extended this issue to 10 years, any advice or knowledge on that?

Also, I should note that no CEL's exist on the truck per the light and my code reader. I have forced codes on the truck by unplugging sensors just to verify that the computer is doing its job and the light works.

 

[joncanyon1]

If you bought it from a dealer then yes your warranty is certainly expired. However, I know that the group of VINs were known by GMC. They actually sent me a letter saying they extended the warranty to 10 years, 100k miles. I only used my buddy's shop because GMC wanted me to come out of pocket and they would pay me back later... I can scan a copy of the letter I got and send it to you when I get home if that would help. Did you receive anything from GMC/Chevy?

 

[joncanyon1]

And the CEL didn't come on for me either. But once you plug into the port, it will give you the code for sure.

 

[Zexy Magician]

If you bought it from a dealer then yes your warranty is certainly expired. However, I know that the group of VINs were known by GMC. They actually sent me a letter saying they extended the warranty to 10 years, 100k miles. I only used my buddy's shop because GMC wanted me to come out of pocket and they would pay me back later... I can scan a copy of the letter I got and send it to you when I get home if that would help. Did you receive anything from GMC/Chevy?

Did not receive anything from Chevy... a copy of the letter for reference would be great!

 

[Zexy Magician]

And the CEL didn't come on for me either. But once you plug into the port, it will give you the code for sure.

I plugged my scanner into the OBDII port many times and never had a code, not even pending codes. Did you mean a different port or maybe a different type of scanning tool? Curious if there is any reason why my scanner tool would NOT show me a code.

 

[joncanyon1]

Hmmm you got me there... All I know is the shop told me they were getting a code when plugged into the port. Not sure if they have a special scanner or not. I wouldn't think so. Bot can't say for sure.

 

[Zexy Magician]

Hmmm you got me there... All I know is the shop told me they were getting a code when plugged into the port. Not sure if they have a special scanner or not. I wouldn't think so. Bot can't say for sure.

Regardless, I appreciate the help! If you can get me a copy of that letter, maybe I can go in and have the dealership check for me to see if my VIN is affected (letter may have been lost in the mail, i moved a lot when i bought the truck). Might just get the compression checked for peace of mind anyways.

 

[joncanyon1]

Yeah man no worries. I have it in my file at home. I'll send to you ASAP. I'm off at 5 on the west coast so might be later...

 

[Zexy Magician]

Welp, just got the P0300! I called the dealership and they ran my VIN, only to tell me I do not have any additional coverage and no outstanding recalls... Any reference # on the extended warranty/letter? Going to do a compression check to verify valve issue first.

The letter for the 3.5L's (found here) states that the warranty is extended to 100k miles/10 years, regardless of ownership. Hopefully the same holds true for the 3.7L's if its the same problem.

 

[joncanyon1]

Man... I'm sorry. Here is the letter I got. I guess it was about the throttle position sensor. Take a look.