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Discussion Starter · #1 ·
The technical service bulletin describes a engine intake manifold plenum pan gasket symptom as internal oil loss and or a spark knock. it describes the test is to allow the engine to reach operating temp, stop engine, disconnect breather hose from air cleaner housing and attach a vacuum gauge to it . Block off the pcv valve and the port it was connect to . Start the engine and let it run for 30 seconds. It warns not to let it build up more than 3 psi. If it dose not indicate vacuum is present, the pan gasket is good. Right? Well my 5.2 passed this test 2 times a month apart. Each time it only took 6 seconds to build up 3 psi. Today in hopes to eliminating the last thing on my list I removed the throttle body and gave it a good cleaning, it wasn't too bad. but I looked into the manifold and saw a small amount of what I believe to be oil by the edge of the pan gasket I taped a q-tip to a long driver and took a sample I think it's oil. I have a misfire/stumble at idle and spark knock symptoms of what the TSB describes is it possible that the pan gasket is bad? Is there another test for it?
As for the upper valve train noise. I can't hear to well anymore allot of ear operations.
I thought it was the rocker arms so I bought a set of Harland sharps roller rockers to eliminate the noise, it got quieter for a while, then returned. It might be a spark knock I just don't know. The plugs are good, The wires are good, I just changed the cap & rotor yesterday. I Replaced the front and back o2 sensors. I use Lucas fuel injection cleaner in every tank of 94. Any Ideas???
 

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Thanks for the advice,it is appreciated.

I saw the 1/4 thick reinforced aluminum plenum plate they are selling .I have some 1/4 plate laying around I'm getting started making it right now.
Is there a reason why they couldn't just. make the manifold one piece ??
 

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I thought I had a bad plenum gasket because I found a small amount of oil but it was directly below the PCV port. No oil or residue anywhere else.
You may try installing a 180* t-stat to see if that helps. Mine had mild spark knock when I bought it, and rather than have the death flash put onto it I installed a cooler t-stat and cooler range plugs. No more knock.

I would take an inspection mirror and look more closely before pulling the manifold.
I have yet to replace my plenum gasket as it hasn't failed since I owned the truck.
 
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