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Discussion Starter · #1 ·
Hi All
Happy New Year .
Well after 145 000 Kilometers (90 100 miles) I've come up with the dreaded P0303 code along with a P0128.
The truck (07 Colorado with 2.9) runs like a dog, missing, coughing and a very rough idle.
I'm resigned to the fact that I will have to fit a new head but what I need to know is what other parts would I need to fit at the same time. I've searched the forum but cannot find a "parts list" of what the job would entail
Bear in mind that I'm half a world away here and what I order from Rock auto now will not get here until March / April so a one time order with all I need would be ideal.
I am not trying to get this done under warranty as I've heard what GM are like in regards to this and our local dealer here is a ..........I'll not go there
I am not a mechanic but have confidence in the private one that will be doing the job. He has done a compression test which has come up with 14 Bar for 1,2 & 4 cylinders and 0 for number 3
Any help would be appreciated
Thanks in advance for any replies
Regards
Jacko
 

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You really need to do a leak down test, that will tell you a lot more than just a compression test. I would bet there are YouTube videos on that job and all the parts required for replacemen.
 

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Discussion Starter · #3 ·
You really need to do a leak down test, that will tell you a lot more than just a compression test. I would bet there are YouTube videos on that job and all the parts required for replacemen.
Thanks Airspeed for the reply.
I'll talk with my mechanic about this.
Regards
Jacko
 

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putting a new-rebuilt head on a high mile block can cause issues aka oil consumption! of course $$$ always comes into play, good luck
 

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Discussion Starter · #5 ·
putting a new-rebuilt head on a high mile block can cause issues aka oil consumption! of course $$$ always comes into play, good luck
Thanks Rodhot, oil consumption seems a small price to pay for keeping the truck going but a good point, thanks
Regards
Jacko.
 

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For the P0128, it's probably either the coolant temperature sensor, or the thermostat is stuck open. I'd put a ODB2 scanner on it and watch the temperature as it heats up. (I have a cheap bluetooth ODB2 reader with the Torque Pro app in my Android phone - great investment.) If its taking a long time to heat up (how is the cab heat working?), then its probably the thermostat, but I'd be inclined to change the sensor first since the thermostat is a PITA to get to.

For the P0303, I'd swap the ignition coil for the #3 cylinder with one of the other ones and see if the problem moves with the coil.
 

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Discussion Starter · #7 ·
For the P0128, it's probably either the coolant temperature sensor, or the thermostat is stuck open. I'd put a ODB2 scanner on it and watch the temperature as it heats up. (I have a cheap bluetooth ODB2 reader with the Torque Pro app in my Android phone - great investment.) If its taking a long time to heat up (how is the cab heat working?), then its probably the thermostat, but I'd be inclined to change the sensor first since the thermostat is a PITA to get to.

For the P0303, I'd swap the ignition coil for the #3 cylinder with one of the other ones and see if the problem moves with the coil.
Thanks Kenzen, good info here. I think the thermostat is not good as my scanner came up with "coolant fluid temperature low" and my temperature gauge has recently never gone above quarter. I have a thermostat ready here to fit at my next service......could be a bigger service than normal.
The results of the compression test point me more towards a bad valve / head rather than a bad coil but good idea to check the coils..........and hope.
My main task now is to find what parts come with a new head and which other parts I should look at ordering along with it.
Thanks again for the reply
Jacko
 

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Typically, the temp gauge should be close to if not slightly over the half way mark.

I don't believe there are "new heads" anymore. There are some ebay vendors offering refurbished heads, some with cams. I'd ask around to see if there's some "old school" speed shops around that can do a quality rebuild on what you have. I believe $300 would be fair for a 4 cyl/16 valves, but ask around. Change the timing chain, the tensioner, the chain guides, and consider the cam phaser and the oil pump "while you are there". If you have sludge in the engine, change the pickup tube and the oil pump, and clean up the engine as best you can.

Good luck!
 

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Discussion Starter · #9 ·
Typically, the temp gauge should be close to if not slightly over the half way mark.

I don't believe there are "new heads" anymore. There are some ebay vendors offering refurbished heads, some with cams. I'd ask around to see if there's some "old school" speed shops around that can do a quality rebuild on what you have. I believe $300 would be fair for a 4 cyl/16 valves, but ask around. Change the timing chain, the tensioner, the chain guides, and consider the cam phaser and the oil pump "while you are there". If you have sludge in the engine, change the pickup tube and the oil pump, and clean up the engine as best you can.

Good luck!
Thanks Kenzen, that's just what I need to know....what to replace or check out "while I'm there"....great advice
Unfortunately there are no "old school" speed shops here.....no speed shops at all and no old school mechanics so I'm a little limited in my options but may have found a "new" head in the U.S. which I think is my safest option. I'll freight the other parts with it so hopefully I can get them all in one shipment .
Do you happen to know, is it the valve seat that is faulty thus affecting the valve and then the whiole head or is there something else wrong with the entire head. As I said earlier I'm no mechanic so I'm at a loss trying to figure out what is the actual problem but resigned to the fact that the replacement head is the surest way to fix it
Regards
Jacko
 

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You have on 07, so the problem with the earlier heads where bad valve guides wore prematurely, causing poor alignment of the valves to the valve seats, and burned out the valve seats should not be your problem. But, burning a valve seat up is not really unusual for any car, and if you've been running cold due to the thermostat, its possible that the air/fuel mixtures have caused lean conditions, raising the combustion temperatures and burning the valve or seat up. If you have a compression problem (and I'll assume its not ring blow by - did you put some oil in the cylinder and retest the compression to see if the oil sealing the rings isolated the compression leak to the valve(s)?)...you have a problem with the head that requires it to be pulled and corrected. I would not stop there - you need to isolate what may have caused the valve problem (if it in fact exists). The temperature running cold is not good for these or any engines. Fix what you know is wrong now, and keep looking for other problems. Clean the throttle body and the air flow sensor. Test your fuel pressure if you can. Anything else will probably "find you" with a CEL.

Keep us in the loop as you beat this down - Good luck!

BTW, do you have heavy oil consumption? Ask the mechanic to look at the valve seals and for sludge clogging the PCV orifice and valve cover baffles.
 

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...just another thought. If you've been running rich due to your temperature problem or some other condition, you may have an excessive carbon build up on the valves causing the leak. What does your #3 and other plugs look like? You may want to try a seafoam treatment on the fuel system to burn out the carbon from the valves - it would be a cheap and safe experiment you can do yourself. There are (entertaining) youtube videos of people doing this to the intake - you'll smoke out the neighborhood, but it may take out carbon that is fouling the valves. Give it a shot...
 

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Discussion Starter · #12 ·
...just another thought. If you've been running rich due to your temperature problem or some other condition, you may have an excessive carbon build up on the valves causing the leak. What does your #3 and other plugs look like? You may want to try a seafoam treatment on the fuel system to burn out the carbon from the valves - it would be a cheap and safe experiment you can do yourself. There are (entertaining) youtube videos of people doing this to the intake - you'll smoke out the neighborhood, but it may take out carbon that is fouling the valves. Give it a shot...
Hi Kenzen & thanks for posts 10 & 11, I will meet with my mechanic tomorrow and show him your advice.....everything is worth a try. What exactly is sea foam and does it have another name?
We're limited here as far as automotive supply store but I'll have a look tomorrow
One question though, will I cause more damage to anything by running the motor (assuming I have to run it while doing the sea foam
Regards & thanks for the info
Jacko
 

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Discussion Starter · #14 ·
Look at the intake manifold / engine top end cleaner.
Thanks for the link.
I've checked and no one has even heard of it here in town
I ordered the parts over the weekend so I'll see how much air freight is to get them quicker
Thanks for the help and I'll post up how we go
Regards
Jacko
 

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For the P0128, it's probably either the coolant temperature sensor, or the thermostat is stuck open. I'd put a ODB2 scanner on it and watch the temperature as it heats up. (I have a cheap bluetooth ODB2 reader with the Torque Pro app in my Android phone - great investment.) If its taking a long time to heat up (how is the cab heat working?), then its probably the thermostat, but I'd be inclined to change the sensor first since the thermostat is a PITA to get to.

For the P0303, I'd swap the ignition coil for the #3 cylinder with one of the other ones and see if the problem moves with the coil.
I was going to say, after awhile I started throwing parts At mine trying to get rid of P0303, when I started replacing coils, I replaced #3 and it fixed it.
 

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Discussion Starter · #16 ·
I was going to say, after awhile I started throwing parts At mine trying to get rid of P0303, when I started replacing coils, I replaced #3 and it fixed it.
Thanks Flying Tomato but would changing the coils affect the compression.....
As I said in my earlier post .........".....I am not a mechanic but have confidence in the private one that will be doing the job. He has done a compression test which has come up with 14 Bar for 1,2 & 4 cylinders and 0 for number 3'.......................
I hope swapping the coils over would make a difference but from what information I have come across the compression test is the decider.
Thanks again
regards
Jacko
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Discussion Starter · #18 ·
You have a valve or piston problem in #3. Time to pull the head...
I think you're right Kenzen.........the parts are ordered....
I'm trying to get a price for airfreight (DHL or FedEx) but I may have to sell one of the kids (or grand kids) to afford this.
It is a 2 month wait otherwise. L.A to New Zealand trans-ship in Auckland and then to us here.
I'll let you know how I go and how the work goes
Regards
Jacko
 

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You really do live off the radar! A buddy of mine is a small plane pilot, and he does his car machine work through his aviation mechanic. You might want to see what is around your local airport. They'd probably do great work.
 

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Discussion Starter · #20 ·
You really do live off the radar! A buddy of mine is a small plane pilot, and he does his car machine work through his aviation mechanic. You might want to see what is around your local airport. They'd probably do great work.
What is that saying?.....great minds think alike...........
My daughters partner is an aircraft mechanic here for a small charter airline and although he is not that keen to actually do the work on my truck he has been great in helping me to decide which parts to order (along with the advice from you guys on this site). Between him and the mechanic I have I'm confident we can do the job.
As far as being off the radar we are about 3 hours flight time to Brisbane (Aust), 1 hour to Fiji and around 3 and a half to New Zealand. Not many people from the U.S. have heard of Vanuatu but its former name was the New Hebrides and it was a staging post in the second world war for troops who fought in the Battle of Guadalcanal in the Solomon Islands so a lot of service personnel and older folks can relate to it when this is explained. The U.S Peace Corps have (or had before Covid) a fairly large contingent here now.
Thanks again for the reply
Regards
Jacko
 
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