Chasing a Miss

[bwebb]

I have 150 psi on all but cylinder 4 its 100 and 4 is firing according to the plugs.
No. 3 is not, threw new plugs, cap, rotor, and wires at it found firing order was
off by 2 wires but still got the miss.

Runs good untill it drops in to overdrive at 45 mph then it chugs.
going to drive it a couple more days and check plugs again if 3 is still not firing
then I think I'll throw an injector at no. 3 and see what happens.

Bought it thinking the head needed valves not sure now.
Anyone else experianced the chugging at 45 mph?
Will check the plugs tomarrow after she drives it some today.

:confused:might be time for :drinking:

[Mudderoy]

I have 150 psi on all but cylinder 4 its 100 and 4 is firing according to the plugs.
No. 3 is not, threw new plugs, cap, rotor, and wires at it found firing order was
off by 2 wires but still got the miss.

Runs good untill it drops in to overdrive at 45 mph then it chugs.
going to drive it a couple more days and check plugs again if 3 is still not firing
then I think I'll throw an injector at no. 3 and see what happens.

Bought it thinking the head needed valves not sure now.
Anyone else experianced the chugging at 45 mph?
Will check the plugs tomarrow after she drives it some today.

:confused:might be time for :drinking:

I'm not sure if this is related, but it might give you something else to think about. I have a P0301 on mine, Cylinder 1 misfire. msmoorenburg "Matt" thinks it's a bad lifter.

[bwebb]

hmmm didn't think about that. Will add that to things to check.
Looks like it needs a new valvecover gasket anyway.

[Cheromaniac]

I have 150 psi on all but cylinder 4 its 100

A loss of compression from the no.4 cylinder indicates that you either have a piston ring blowby problem or a valve sealing problem.
Try repeating the compression test with the cylinder in its normal "dry" state and again after adding a teaspoon of oil to the cylinder. The oil will form a temporary seal if it's a blowby problem and raise the compression, whereas it'll have no effect on compression if it's a valve sealing problem.
If it turns out to be the latter, pull the valve cover and check the valve springs. A weak or broken valve spring will allow the valve to hang slightly open and combustion gases to escape past it, causing the chugging that you described. If the springs turn out to be OK, the problem is likely to be a burnt/bent valve or damaged valve seat and you'll need to pull the head to investigate.

[bwebb]

Will check that out this weekend when I cahnge the valvecover gasket.
Thank you for the reply

Bill

[bwebb]

Found the miss after checking the valves and replacing the valve cover gasket.
It was a bad wire between the ecm and injector. so we just ran another wire
and it runs GREAT... Nice and smooth

Can't wait for the lift to get here. Just waiting on taxes then I can pull the
trigger on the lift. One more week and I'm on vacation. Wish I had waited another
week maybe. Soon as I place the order I'm starting the tear down. Got a copy
of the install instructions so I know how far to go with it.
We are ready, getting all pumped up about hitting the trails SOON.

[Cheromaniac]

Glad your engine's running much better but what about the low compression on the no.4 cylinder?

[bwebb]

It was late last night when we got finshed so didn't get around to checkin
compression again. Kid asked if I had the tools to pressurise the cylinder for a leak down
witch I do just ran out of time last night.

If the nephews brake light nitemare hadn't took most of the day to fix we would
have had more time to work on the cherokee. Nephew has a toyoda or yoda
we call it.

With any luck after I get the backyard and alley cut will get to dive back in.
Still gotta tie up the added wire and make sure we got everything back in place
last night.
The bad wire just made the $500 94 xj a nice find.