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1994 XL, E40D, 5.0, rear lsd, front auto hubs
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Discussion Starter · #1 · (Edited)
Today I just did a compression check on my 302. What's the damage? This is my first time.
Yesterday I pulled out the spark plugs, picture below. Changed them with ones I gapped to 0.055 and changed all the plug wires. The car did not run noticeably better just fyi.
I'd love it if you guys could give me advice on the smoking issue. It smokes a lot, does not smell like coolant, is not black, is between white and blue, mostly white, hard to see any blue.
My first impressions from looking at the results and doing some research:
MILEAGE: 137K.
-Spark plugs:
Driver bank porcelain is coffee colored, seems okay, all dry, very little carbon deposits.
Passenger bank has a lot of carbon deposits, rich condition from leaky injectors? plug 3 was very wet, did not dry overnight so not gas, oil maybe, the wire at that plug was a little damaged where it rubbed on something so maybe poor ignition and that's why it was wet?
-Compression
Driver bank is overall dramatically higher compression than passenger bank. Also large difference between dry and wet compression. Firewall cylinder (8) a lot less compression than the other three.
Passenger bank has a lot less compression than driver bank. The difference between dry and wet compressions is very little for all cylinders on that bank.

I hope some of you guys can talk some magic about what is going on, could be going on, parts failing, bad rings or bad valve seals or bad valve stem guides, head gasket, bad injectors, etc.

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If the PCV is routed right over cyl #8 buy a few feet of vacuum hose and swap it with the power brake port on the intake. The PCV dumps junk and it is better more central so all the cylinders share it as opposed to just dumping it all on #8.

A wet compression test should always be a little higher as it seals the rings more, but can indicate rings not sealing as well.

A leak down can see if it is getting past the valves.

Although uneven those numbers don't look too bad.

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1994 XL, E40D, 5.0, rear lsd, front auto hubs
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Discussion Starter · #7 ·
How is your PCV valve routed?
All I know and can see is that the pcv valve is in the passenger valve cover above cylinder 4. A vacuum hose comes out of it and travels under the intake manifold towards the driver side. After that can't tell where it goes but aren't these things routed into the intake manifold?

Today I went and picked up a leak down tester. It snowed a lot so I probably won't do it today. Tomorrow morning.
How do I do this?
How to put a piston at TDC and how to lock it there while I pressurize the cylinder?
To check for valve stem seals in a leakdown test, we listen into the valve cover(pcv grommet hole)?
Is the oil filler neck on the driver side valve cover open to the valve covers and crankcase both or only the crankcase and does not connect with the valve covers?
I am trying to find out if I could do an easy valve seal job or a much harder piston ring job. I know that piston ring leaks you hear it from the oil filler neck.


If the PCV is routed right over cyl #8 buy a few feet of vacuum hose and swap it with the power brake port on the intake. The PCV dumps junk and it is better more central so all the cylinders share it as opposed to just dumping it all on #8.
I'm going outside as we speak to see where that pcv hose connects to and if it goes into the valve cover at #8.
Are you suggesting dumping oil and pressure into the intake manifold instead of the valve cover? My engine is already smoking this would make it even worse wouldn't it?


Thanks people my head is spinning but at least I have things to do and test
 

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1994 XL, E40D, 5.0, rear lsd, front auto hubs
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Discussion Starter · #8 ·
Okay I just went to check where the pcv hose goes to and I am left without a clue. There is nothing going on above cylinder 8 on the valve cover.

Passenger valve cover has the pcv valve and hose at cylinder 4 that goes under the intake manifold to a mystery location.
Driver valve cover has the oil filler neck and cap above cylinder 1 as well as a hose coming off the neck and connected straight into the air intake right before entering the throttle body.
 

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1994 XL, E40D, 5.0, rear lsd, front auto hubs
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Discussion Starter · #9 ·
Wow I think I found where the pcv hose ends up. I found this picture which seems INVALUABLE in the current context.
Basically it plugs into the back of the throttle body plenum and does look like that plenum passage is the one leading to cylinder 8. So hook my brake booster to that instead?
 

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Basically, both the PCV and brakes pull from a vacuum source. The brakes just suck air, the PCV sucks oil vapors and such. The PCV should be attached to the intake port that allows all the cylinders to share the crap the PCV draws in. At least on the 351 the factory routed the PCV to a port literally right at one cylinder so that cylinder got all the junk, eventually leading to poor compression in #8 and eventual failure of that cylinder.
I actually have the receipt the PO left behind indicating motor failure due to no compression in #8 at about 100k.
I am not sure if the 302's had the same problem, but it would not surprise me.

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1994 XL, E40D, 5.0, rear lsd, front auto hubs
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Discussion Starter · #11 ·
I found where my PCV hose routes. Not at all in the back. It routes around the back of the intake, wraps around it then comes above the intake on driver side and plugs into the top of the intake. I am not sure what cylinder it dumps on but could be all of them, being at the top, or maybe just one bank. In the picture I hold the end that connects to the pcv valve and below it is where the hose comes into the intake plenum. I replaced the valve. Ran it for a while and still smoking. The car did not run any differently from before. While removing the pcv while running and also the oil filler cap, I noticed light smoke coming out of both openings. Having the pcv off did not stop the motor from smoking so I now believe oil is introduced into the cylinder on its way up through bad rings or down from the valve seals through either intake or exhaust valves.
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