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BAD compression... is it over?

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Old May 19, 2009 | 04:07 PM
  #1  
LS1Steve's Avatar
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From: Encinitas, CA
BAD compression... is it over?

After having an intermittent idle problem (sometimes shuts off at stoplights) and looking over everything, replacing sensors, and a good tuneup, I did a compression test. Results as follows:
Cyl 1 110psi
Cyl 2 45psi
Cyl 3 60psi
Cyl 4 45psi
Cyl 5 150psi
Cyl 6 10psi

Is there anything I can do short of a rebuild? It would cost more than the truck is worth, so I'm not to fond of the idea. Has it run it's course?
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Old May 19, 2009 | 04:11 PM
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From: maple ridge, British Columbia, Canada
3.4L swap??
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Old May 19, 2009 | 04:36 PM
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From: Temecula Valley, CA
There is the 3.4 swap option, install a lower mileage used engine, rebuild, or install remanufactured. I've seen reman'd from about 1700.
There was an entry on craigslist near me for a 5vze and trans/transfer case for 1500, no harness though.
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Old May 19, 2009 | 05:32 PM
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From: maple ridge, British Columbia, Canada
Might be easier to find a wrecked truck and buy the whole shibang.
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Old May 19, 2009 | 06:17 PM
  #5  
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RMA
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From: San Jose ,Ca
1Uzfe , LS 400,s are running around $800-1500 right now , running 120,000-220,000 miles on them .
Ive been looking on craigslist daily, but they are selling quick.
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Old May 20, 2009 | 05:43 AM
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Have you done a cylinder leakage test? I have seen where one or more valves haven't fully seated due to bad valve adjustment, so the cylinder never sealed. It could be as simple as a valve adjustment. If you have an air compressor, i think Harbor Freight had teh leakage testers for about $20.
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Old May 20, 2009 | 05:53 AM
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Agree with last post. I suspect there are very few 3.0's that have ever had their valves adjusted because its so difficult to perform and very expensive. If you are not burning oil out the tail pipe, then your valves need adjusting. Over time they retract into the head and loose their very small clearances from the factory. Pack a dam lunch if you try and do it yourself. I suspect the dealer would want at least $500 to do the work. I have used a very large flat blade screwdriver to hold the valve spring down enough to remove the adjustment shims with a magnet. I have had some luck swapping them around, flipped over for a new surface, and getting the valves back in their adjustment clearance ranges.

My $0.02 but been there and done that....
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Old May 20, 2009 | 06:07 AM
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From: atlanta
As already stated, a cylinder leak down test is waaay more acurate than a compression test alone. once the combustion chamber is pressurized you'll be able to hear where the air is leaking.
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Old May 20, 2009 | 07:18 AM
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From: Encinitas, CA
Originally Posted by desertcox05
As already stated, a cylinder leak down test is waaay more acurate than a compression test alone. once the combustion chamber is pressurized you'll be able to hear where the air is leaking.
where should the crankshaft be turned when I leak test a cylinder? I assume top dead center.... easy for cylinder 1 but what about the rest? And I figure I'd have to have the valve covers off to identify the leaks right? This will be my first leak test...
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Old May 20, 2009 | 07:39 AM
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Here is the one I got. i am pretty sure it was on sale when i got it (they always have sales) but still $35 isn't too bad. Basically hook it up, and remove your oil fill cap and radiator cap. If you see it bubbling and hear it out the radiator, you have a blown head gasket, if you hear it out the oil filler cap it's most likely bad rings, if it's out the exhaust or intake, then it's the corresponding valves.
http://www.harborfreight.com/cpi/cta...emnumber=94190

BTW, yeah TDC for each cylinder. Once you find #1, you can go in firing order and use the distributor to help you verify, the rotor is going to point ot the wire of the cylinder at TDC.

Last edited by MrPeepers; May 20, 2009 at 07:42 AM.
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Old May 20, 2009 | 08:22 AM
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From: atlanta
make sure the piston is at the very top of the stroke. if it's not the compressed air will drive it back down. MrPeepers is good on everything else
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