2002 Trans Am Misfire on 2 cylinders Puzzled
2002 Trans am LS1 5.7
I rescued the car so I have an unknown history of how it ran before it sat for almost 10 years.
I am fighting a Misfire on cyl 1 and 3.
So Far I have verified it is not The coil, Wire, or Plugs
Also it is not the Fuel injector, I changed it out and still missing.
Compression is 180 on cyl 1 and 155 on cyl 3, 180 on all the rest
The miss goes away when revving the engine.
Changed the Intake gaskets AND even got another ls1 intake to put on and same issue
Vacuum is a steady 25
New Spark Plugs
New Battery
New PCV
Cleaned the MAF with maf cleaner
Cleaned the throttle body (it was really clean already)
Car only has 22k miles on it, was sitting outside for over 10 years
Wire brushed all the grounds
Here is a Video of what I have done. I have a tech 2 scanner, but admittedly it is beyond my skill level to understand all the functions
I only have access to a tech 2, but my neightbor has the most bad to the bone autel scanner, but he doesnt know how to use his either.
Steak dinner to the person who figures this out!! I am lost.
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- Andy.MacFadyen
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" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
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Besides the misfire, how well does it run? A V8 with one cylinder down should still move itself down the road.
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It looks like you've got little air going in, therefore little leakage.
I turn mine up to 40lbs. That's where top dead center becomes important because if the connecting rod isn't straight up and down, the air pressure can push the Piston through the rest of a stroke.
Also I wouldn't remove the rockers or any part of the valve train. You could be masking a problem that could be making the valves hang open.
"Ground cannot be checked with a 10mm socket"
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I took the rockers off because i really wanted to test the sealing of the valves without laboring to find actual TDC
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Here is the Crank Relearn and the Fuel trim data.. Thoughts?
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- Adam Davis
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also your fuel trim looked real good so you need to get your o2 sensor data up, need to see if running rich or lean if its switching perfectly you've got fuel issues.
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Notice how when you disabled other cylinders that another cylinder would start counting up, all though considerably less than the actual misfiring cylinder.
It also appears that the computer is accurate in flagging the missing cylinder based on the results of your testing.
I think it would be safe to focus your efforts on cylinder 3. Your compression test seems to back this up as well.
As for your last post, I don't notice any problem with your oxygen sensors. Looks like maybe b2s2 took a little longer to heat up and become active, but certainly nothing that would contribute to a single cylinder misfire.
Cylinder 3 being low on compression points to a mechanical issue.
The misfire that goes away off idle points more specifically to a valve sealing issue (in my experience).
I trust that you know your tools better than I do, and after reading the instructions for that harbor freight leak down tester I believe you are using it as described, but I don't trust the results of that test/tool.
Personally, I would repeat that test on cylinder 3 at true TDC with the valve train assembled and dial up the pressure or see if you can borrow a different brand tester from your local parts store.
I completely understand why you performed the leak down test like you did, but by removing the rocker arms you're entirely removing the camshaft, pushrods and lifters from the equation.
I just had a Malibu yesterday with a valve sealing issue and I couldn't pin point the source of the leak until I cranked the dial up to 100psi. Then you could hear air coming out the exhaust.
I hope you get it figured out, keep us posted!
"Ground cannot be checked with a 10mm socket"
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