Starting the deep dive into motor work... opinions?? Direction??

DiscoinAK

New member
Nov 29, 2019
1
0
Alaska
Hi all... thanks for the add...

Have a 2004 V8 disco 2 w/145k miles that I just bought used. Vehicle starts up and runs but is evident that it had a misfire or something going on. Pulled the codes and had multiple misfire codes on cylinder 2,4,6,7. Replaced spark plug wires and plugs with minor improvement. Up until this point the truck still starts, idles and drives but lacks power, although no over heating or coolant smell in the exhaust. Oil isn't milky. Did a compression test, plugs out, wot, pump/ spark disabled. Ended up having the 2 middle cylinders on driver side with 0 and 8psi compression. Poured oil down each cylinder and did another test with no change in pressure. Used bore scope to visually inspect all cylinders. Both bad cylinders have heavy carbon and oil deposits with no visible damage to piston heads or cylinder walls that I could see. All other cylinders had 180-190 psi. Most looked normal with some carbon build up or fairly clean.

At this point I'm leaning towards a valve or ring issue unless there's something else that could cause oil to enter the combustion chamber. When I get back home I will be pulling the heads to take a closer look. I'll also be testing the coolant for co2 to check for a cracked block.

Does anyone else have some further insight, experience or suggestions in this issue? Sorry if there's any info that I missed.
 

jastutte

Well-known member
Nov 10, 2009
461
71
i can't help evaluate but while you're in there consider upgrading the camshaft. on that engine with that mileage you could use it anyway.

anecdotal only, but i am seeing the occasional post about walked cam bearings on the 4.6 engines at higher mileage. it also did happen to me and i had a Crower 53229 Camshaft installed. it does seem to wake the engine up a little and gives slight (very slight) mpg improvement.
 
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4Runner

Well-known member
May 24, 2007
660
110
Boise Idaho
Sounds like you going to travel thru there anyway on your way to the heads, but I would check your valve train while you are disassembling things. Watch the rocker arms while you rotate the motor. Other than a valve that is stuck open for some reason, bent broken pushrods, wiped cam lobe, then it could be a head gasket blown out between the two cylinders. Sounds like your going in the right direction.
 
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CBiDrive

Well-known member
Sep 20, 2007
108
22
Parker, CO
I am also leaning towards head gaskets as your major prob if you are not seeing major scoring on the cylinder walls. Definitely isolate the issue before throwing parts at it. If you are pulling the motor you might as well install new front and rear main seals, timing chain/gears and oil pump gear. For little $$ it refreshes the motor nicely.
 
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Swedjen2

Well-known member
Sep 12, 2018
594
127
California
IF you end up pulling the engine, get a top-hat block or have top-hat liners installed or you will be kicking yourself when the liner(s) finally do leak...leading to sadness, anger and regret.
 
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