Chasing P0302

[Archaic2021]

97 Silverado 5.0

Compression is 120lbs

New wires, cap and button.

Have not replaced plugs but they look bran new.

Still getting a miss on cyl2.

Idles great...can fill the miss a little between 1500-1800rpms after that runs very very smooth.

What should I check next.

 

[Schurkey]

Depending on your altitude and cranking speed, 120 is pretty low. Or your gauge isn't accurate.

I'd consider a cylinder leakdown test to check for valve leakage.
Swap the spark plug with another cylinder, see if the miss follows the plug
Have you tested the plug wire to see if it's "New Defective"?
Any vacuum ports connecting to #2? Intake manifold gasket squeezing out-of-position?

 

[SUBURBAN5]

I would do a fuel pressure balance test

 

[Archaic2021]

How would I do that on this truck?

 

[SUBURBAN5]

Hook up a guage and hook up a scanner. Select fuel/injector pressure balance and it will walk you through it. You record the info like 60 drop to 48 piston 1 60 drop to 48 piston 2 60 drop to 25 piston 3. Bingo found an issue with that injector. This is an example btw. If there all the same or within 1or 2 psi your probably fine and need to proceed to another test

 

[81nascar]

Depending on your altitude and cranking speed, 120 is pretty low. Or your gauge isn't accurate.

I'd consider a cylinder leakdown test to check for valve leakage.
Swap the spark plug with another cylinder, see if the miss follows the plug
Have you tested the plug wire to see if it's "New Defective"?
Any vacuum ports connecting to #2? Intake manifold gasket squeezing out-of-position?

I would agree with that.. That's getting low. stock is around 150ish psi with about -20 psi for max tolerance.. according to my service manual.. Check it again and if the same, proceed with a leak down test before you throw any parts at it..

 

[Archaic2021]

I'm gonna go get a better compression tester. I was using one of the old old ones you just hold in place, but the ru bee is kinda cracked and soft..gonna get one of the ones that screw in...even cheep ones are like 30 bucks.

Plug on the left came out of cyl 2

You must be registered for see images attach

 

[1997]

Looks like you found your issue.

 

[Archaic2021]

Looks like you found your issue.

Have I?

I still need to get a good tester to re-test the compression. The one I was using was so old the glass over the gauge blew off when I re-tested it.

I changed plugs around...still missing on cyl 2


Also..the second bolt on the passenger side of the intake was loose...I could turn it 3 full turns, I couldn't get to the bolt that's behind the ac line on the front to check it, I'm wondering if the intake is leaking right there.

 

[1997]

you have contamination getting into cylinder 2.
possible causes:
- oil from valve seals, rings, etc.
- head gasket failure, cracked head
- leaking intake
- etc ..... compression test would be useful