P0420 is not a vacuum leak. As you thought it's 1/1 catalyst efficiency. You may have a bad catalytic converter.

Some of the faults only appear after so many "trips" which is basically a cycle of the systems. I'm not positive about a '98 but later models used the downstream sensor to check converter efficiency. It may be a slow O2 sensor but your misfire could have also damaged the converter.

On the rings, just drive it normally. Some occasional heavy acceleration and then deceleration is good. You don't really have to do anything drastic to it. I'd suggest a conventional oil for break-in too.

The lifter may be bad or possibly has some dirt in it from the rebuild. See what happens in a few days with it.

 

i am 95% positive ive got a dirty injector, truck ran on 3 cylinders for a bit, then ran fine, then back to 3 cylinders

 

Are you sure it's the injector? How noisy is the lifter? If it's collapsing the valve won't open and you'll misfire.

 

Where does this pin/zip tie go? what hole?

On the rings, the most important part is to unhook the breather tube. You want the crankcase slightly pressurized when you seat the rings. We unhook the vacuum system on our motor for every start, then spin it on the starter until the 15psi oil pressure switch activates, then reconnect the vacuum line once the water temp is 150 degrees (which puts crankcase from slightly pressurized to 8 inches of vaccum at idle, and takes oil pressure from 80 to 60 psi). This prevents dry starts, and always makes sure the piston rings are seated by the positive pressure on the combustion side, and not the vacuum on the crankcase side. Also, put the pistons in dry, don't wipe the cylinder walls in oil, as it will prevent the rings from seating.

 

the lifter gets pretty damn loud, but i can hear the engine firing on all 4, i can really only notice it running on 3 when im at idle speed... once i accelerate, it smooths out until i let off, and then if i tap the gas pedal 2-3x it may go away for a bit, i stop somewhere, get back in the truck then starts running on 3 when i crank it up, then when i take off and come to a stop it will be running fine, so i think ^ This issue made P1391 WORSE



"Factory replacement distributors are equipped with a plastic alignment pin already installed. The pin is located in an access hole on the bottom of the distributor housing Plastic Alignment Pin It is used to temporarily lock the rotor to the cylinder number 1 position during installation. The pin must be removed after installing the distributor"

"If original distributor is to be reinstalled, such as during engine overhaul, the plastic pin will not be available. A 3/16 inch drift pin punch tool may be substituted for plastic pin.
5.Remove camshaft position sensor from distributor housing. Lift straight up.
6.Four different alignment holes are provided on plastic ring, Note that 2.5L and 4.0L engines have different Pin Alignment Holes"

 

Next time you hear it running on 3 cylinders, verify it. Pull the plug wire to find out which cylinder.

You could have a bad injector. How are the harnesses, clean and tight?

Have you double checked the rocker arms?

 

P0304 has popped up this morning, Cyl #4 Misfire

Spark is good

Spark plug looks a bit too orange, (no oil though)

im sure my #4 injector is dirty, i bought a harness plug for injectors, now i need to figure out how im going to power them to keep them open while i clean em.

I suspect the#4 injector is dirty, i had them in a bag rolling around for a few weeks, i had intended to get them cleaned, but had to build my engine Quickly

EDIT: i just checked my rockers and they look to be fine

 

I took the #4 injector out, cleaned it with the injector open, it sprayed pretty good... thought i solved the issue, minutes later she starts running on 3 cylinders again, so now im gonna swap the #4 injector with #1 and see what happens

Swapped the injector out to #2 and #4 is still misfiring.............. =/

 

Like dan said, do the old school trick. When the engine is missing, pull the plug wire off the distributor, then plug back in and repeat for each wire. As you drop holes, it should get worse. When you unhook a wire and the motor stays the same...that's the dead hole.

 

Did that, and #4 is the problem

Im hoping the lifter is causing the misfire, but because i overheated the engine to hell, im thinkin #4 on the head is damaged, only thing left to do is

Change lifters

Leak down test

theres a 2.5 in my local yard at the moment so i should go pull the head ASAP