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RIP Forrest
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12,421 Posts
Discussion Starter #1
From what I'm seeing the warranty only carries to 100k? I'm about 99% sure I have a bad valve(s). I have had a misfire on #4 for quite a while, I have done all the obvious, plugs, coil, etc. my power and mileage is crap and the truck runs rough. National cylinder head shows $400 for a head completely set up, with core exchange. My truck has 105k, and is an 08 I bought in March 08 so it no doubt has one of the first run of the 3.7 heads. I'm going to see what the dealership says and if there is no luck there I'm going to order one, tired of low power and 13 mpgs. I will keep y'all posted
 

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RIP Forrest
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12,421 Posts
Discussion Starter #2
Haven't thought much about this because we have been planning a vacation but I price checked a reputable local head shop and got quoted $200 for a full go through and refinish plus valve price if any need replaced. Dealership wants $112 for a leak down test then they 'might' cover a portion of any repairs needed. My brother is borrowing the truck for the next week or two but if I get it back before we leave Sunday for vacation I will try to get the head pulled and to the shop
 

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1,104 Posts
oh man, im not liking this post.. let us know which way you go about fixing it!
 

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RIP Forrest
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12,421 Posts
Discussion Starter #4
My brother in law is pretty sharp on gas and Diesel engines and after telling him my issues, how long it's been going on he believes it's a stuck open injector. Smells strong like raw fuel when it's running and from a cold start it almost always backfires. They are only about $30 each so I ordered one, should get it in this weekend to see. If that's not the issue he has a gauge to use for a leak down on it.
 

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Premium Member
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5,710 Posts
A fuel pressure check should tell if you if you have an open injector.....because the pressure will bleed off.

I had an injector fail several years back on an engine of mine. I thought pressure may slowly bleed off giving my symptoms. But I energized the pump, pressure rose and instantly fell off.

A compression check on that cylinder also confirmed....as well as the hydrolock condition as the cylinder was willing with fuel.

Could possibly be a regulator as well...too much pressure allowed to pass causing your rich condition. If there are regulators on the 08's. I do not recall if the regulator went away at some model year, such as the pump acts as a regular as well removing the need for a physical regulator. But I can't really remember about that part. Others will know for sure though. A fuel pressure check will confirm that too. Pressure should be stable. If not, then regulator is the problem. Had that happen on the same vehicle...for some reason the engine didn't like 80psi of fuel. haha

Good luck.
 

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RIP Forrest
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12,421 Posts
Discussion Starter #6
Still throwing a cel. I pulled the battery off to get it out of the way for the injector swap so it was clear when I started it back up. Not sure how that works but it came back on with a few minutes of running and showed the same cyl misfire and o2 sensor code also. So whenever I can I'm going to get my brother in law to bring his gauge over and do a leak down on it.
 

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RIP Forrest
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12,421 Posts
Discussion Starter #7
Just ordered a reman head from nationalhead.com . No 3.7 build they said about a week to get one together and should have it by thanksgiving. Total ran $470 shipping and all, no core charge as long as the old one is returned 30 days from the date received. Wanted to get it before it gets too cold and I end up smashing knuckles in 30 degrees.
 

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Anybody have a how to on replacing the head? My 2.8 is dying with a random misfire BS this is alot cheaper then a whole engine.
 

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maniac mechanic
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5,779 Posts
Did you do a leakdown test before buying a new head? If the problem turns out to be timing chain or bottom end related you will have spent the money and effort and be in the same boat.
 

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RIP Forrest
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12,421 Posts
Discussion Starter #11
Word of advice don't use national cylinder head exchange. They charged me $470 for the head back in November now they won't return calls, emails or anything. I was quoted cheaper at a local shop to rework my head but I wanted to exchange to save down time, lot of good that did. I dealt with Odessa cylinder head out of Florida on the sonoma head and had good luck. At this point I'm just going to pull it and let the local shop do it when I get time
 

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Premium Member
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Well with any luck you still have the head in your possession because it appears the national cylinder head exchange took your money & ran with it and closed down the website.

I'd try to locate a cylinder head machine shop in your area with a T&S 3D seat cutting tool so they can perform an accurate three angle valve job.
 

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RIP Forrest
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12,421 Posts
Discussion Starter #13
There is a good local shop I had originally planned to use, but knowingly paid about $200 more than they quoted me because I didn't want down time. I had looked at national cylinder a few years back, they had a voicemail around Christmas time about a family emergency and I haven't been able to get in touch with them since and the site is no longer up. Idk what happened with them.
 
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