Do the leakdown test to see if it's coming through the head or past the piston rings.

We had a hole on our motor flow 34%. All of it was past the rings. Pulled that piston/rod out, and all the gaps on the rings were lined up. Turned them around and put the piston back in, flowed 7%.

 

Spray some brake or carb cleaner around the manifold gaskets and see if the rpms change. Maybe, just maybe, the manifold isn't sealing well.

 

Went to the store just now, and it was running on all 4......

 

So do we know that #4 is firing, and that you don't have a bad post on the distributor cap? Hold the plug with a pair of insulated pliers, and touch the threads to something steel. Most use an accessory mounting bracket.

If it has spark, then it's lacking fuel or air.

Get a set of leakdown and compression gauges. Run the leakdown first- see if it's blowing past the rings or valves or through a crack. Then run a cranking compression test. Should be over 100psi I would think. If the intake valve wasn't (fully) opening, it would be pulling air past the rings or choking at the intake valve. If the exhaust valve isn't (fully) opening, pressure would be passing the piston rings and chamber pressure would be higher.

You can check that with the valve cover off, though. Just see if the rockers come up and down as much.

Check the injector with an ohm meter.

 

shes got plenty spark, i know so ,im gonna give new lifters a shot before renting a leak-down tester, if i have to pull the head from the 2.5 in the yard, i need to do this SOON

 

I would think you could see a failed lifter from watching the rocker arms?

Zapped yourself pulling the plug wires I take it?

In the 3 days it'll take lifters to arrive, might as well rent that leakdown tester and compression gauge...

 

oh hell yeah i zapped myself, i thought the pliers i used woulda worked, Nu-huh ...... Ignition systems Good

ill run it without the valve cover and see how the lifters/rockers function

EDIT: Rockers/lifters seem to be functioning for #4 cylinder despite the tick

 

So you've swapped fuel injectors, verified spark, verified the valves are opening fully....you aint the only one at a loss!
All i got left is leakdown and compression check.

 

Both lifters for #4 are locked up, looks like i need to do a leak down and then go from there, cause i checked the compression a few days ago, Mind you they are new rings, that cylinder tested 125psi 3 times in a row, and my #3 cylinder had readings of 120-125 and its not misfiring at all...

 

Both lifters for #4 are locked up they are not moving at all?

That can be a problem to fix if the cam lifter heads have mushroomed at all. The cam lobes could become damaged also if the lifter is jammed.

Did you install new lifters?

I know they offer a higher quality lifter for this engine that tells me something ... get them.