Misfire I am having troble fixing

[79 Wolfpack]

I did a tune up on my Cherokee.

I did the cap, rotor ,wires , coil , plugs . Timing is set at 10 Deg btdc.

I had it running perfect. Took on a dvive to go wheeling.

On the way home it started missing.

I has spark , fuel, and 150 psi on all cylinders.

Seems to be missing on the #2 cylinder .

What do you guys think it could be.

[babywag]

I did a tune up on my Cherokee.

Potentially faulty ?new? parts? Quality is pretty lacking these days.
Check that plug wire? Or swap an old wire on.

I bought a set of new ACDelco wires when I did tune up on my Caprice.
2 were crap right out of box.
Sent turds back for refund. Some Duralast gold(s) from AZ were cheaper and were actually decent quality. Better warranty as well.

[Tanker]

I would start by taking if you have one timing light. Start by checking the wires next to the plugs. If they all light up then loosen the plug wires, pull them off one at a time and see if there is a difference. As a engine builder I've had people complain that they had a engine miss. One was a plug not working one that had a rotor fall apart the others were wires. Start small an simple an go from there. Plug wires pulling can be fun if not careful, I use a pair pliers with a wire to ground.

[79 Wolfpack]

When I pull the #2 plug wire no change to engine while running. And its header
Pipe is cold . I have pulled the wire and put a plug in and it is sparking .

[joe]

When I pull the #2 plug wire no change to engine while running. And its header
Pipe is cold . I have pulled the wire and put a plug in and it is sparking .

Use the plug that's in the block. What color is the spark? Blue is good. Yellow-orange is weak.

[wiley-moeracing]

sounds like a bad plug, install new plug or swap plugs around and see it changes. if you drop a spark plug they are shot, throw them out and get a new one, can happen at parts store also.

[gophman]

Did you drop a plug when installing? Pretty common for a dropped plug to close the electrode gap and not noticed.

[Heavy_Metal_Thunder_81]

sounds like a bad plug, install new plug or swap plugs around and see it changes. if you drop a spark plug they are shot, throw them out and get a new one, can happen at parts store also.

THIS. Had it happen too many times to me

[79 Wolfpack]

Turned out to be one broken valve spring .

[wiley-moeracing]

easy fix if valve did not drop

[68glad]

I has spark , fuel, and 150 psi on all cylinders.

[79 Wolfpack]

easy fix if valve did not drop

Ya I got lucky Valve didn't drop . All fixed up with new spring runs good .
Cylinder tests good 10% leak down .

[JeepJeepster]

Maybe it wasnt completely broke and still closed valve with the starter turning engine??? Kinda odd...

[wiley-moeracing]

makes sense, would miss when engine is running causing the valve to bounce but just enough pressure to stay tight when just cranking. I have had broken valve springs that turn just enough not to come apart and drop the valve, sometimes you get lucky.

[68glad]

Maybe it wasnt completely broke and still closed valve with the starter turning engine??? Kinda odd...