evanlove

Thanks for letting me know Cruiser54 is no longer here... ... may I ask, is the information he posted above about which 4.0 I can put in my '88 Comanche considered to be true and correct by everyone who knows such things? Thanks

Thanks for responding... ... I want to keep the manual... ... it's Peugeot, but I like manual... ... it's just that most of the used 4.0's around here (Pueblo Colorado) are out of automatic Cherokees. So, wondering what I'll need to do to put the flywheel and clutch from my knocking (hard knocking) 4.0 onto a 4.0 from an automatic... ... or if I should hold out to finally find a 4.0 from a manual Cherokee. Thanks

Along with putting my Renix stuff on the H.O. long block... ... what would I need to do if my '88 Comanche is manual and the H.O. I buy is from an automatic? Thanks

Thanks everyone, I'm not in the same state as the Comanche right now, but as soon as I get back to Colorado I'll look into these things and report back... ...and make a video with the sound too

That's an interesting thought... ... I'll look into that

It's a manual trans, so not a flexplate, but I like the alternative things to consider. It's a higher pitched slapping noise, very loud, but doesn't sound like a mere lifter tick (i wish it was) unless this particular engine can make that level of noise from just a lifter. I would think a rod or main bearing would be a lower tone knock (rather than a slap) from audibly deeper within the engine, but i suppose either could cause an actual piston slap. Any thoughts on why it sounded really good before firing and had good oil pressure, but then sounded really bad when firing and oil pressure dropped? I would think higher rpm would have higher, not lower, oil pressure. So, ya, the sound was loud enough and more slappy than knocky, that I wasn't completely sure it wasn't external to the engine... ... though the mind plays tricks when it is in denial and I really didn't want to hear what I was hearing. Some smoke did rise up from the open circle in the valve cover where the hose to the air box should be for a little while after I shut the engine down (previous owner replaced the air box with one of those cone shaped air filters and left the air hose to the valve cover open). Also, there was a valve cover gasket, unopened, behind the seat... ... and it looks like newer freeze plugs in the engine... ... truck has 235k miles... ... had new tires and exhaust put on just before they parked it... ... tow bar was on the front as if it was towed into place... ... I did have to replace the fuel pump to get it to fire, and regap the plugs... ... it was being held as collateral for a personal loan and then the owner that owed the money died and never returned for the truck... ... so, no previous owners information on the trucks condition other than the odd collection of clues (new tires and exhaust on a truck that was towed into place, valve cover gasket behind the seat, dead fuel pump when I got it, plugs gaped at 55 wouldn't fire until regaped to 35, aftermarket freeze plugs in engine) I appreciate any feedback, and, I will pull the valve cover and pan and see what can be seen and feel what can be felt from there. Anything I should try before wasting all the brand new oil and filter? I guess I could try pulling one spark plug wire at a time and see if that changes anything. Thanks Evan

Thanks everyone. I changed the oil and filter. The oil pressure seemed good when I was just turning it over but not firing, and it all sounded good then... ... but as soon as it fired, it made that very loud metal on metal slapping noise... ... and the oil pressure went down. At first I thought maybe the slapping noise was external to the engine. I looked around for something moving and physically hitting it from outside. My friend listened to it from the passenger side with a mechanics stethoscope against the engine and he quickly thought it was the crank jumping around inside (i don't know his level of expertise with cars) so I shut it down. Accelerating the rpms did not quiet the engine. If it is fixable I'd love to not rebuild this engine. The truck sat a long time, but had brand new tires and exhaust installed just before being parked, though it did have a tow bar on the front of it, soooo?

I didn't run it long at all because it sounded really bad. Oil is new, new filter, no visible sludge through the fill hole. A friend (expertise unknown) said it sounded like main bearings out and crank clunking around. Sounds like piston slap to me, but I'm not familiar with these jeep 4.0 engines. It sat since 2007 i believe, condition before that unknown. Any thoughts?

Just got my first Comanche and got it to run after it had sat outside in Colorado for 15 years. It sounds like a serious piston slap when it's firing, so I shut it down. I got no history with it when I bought it, so I have no idea if it was parked in good running order (had brand new looking 15 year old tires and new looking cat-back exhaust, so, maybe) or if this slappy sound was there when they parked it. Is there anything other than piston slap that could cause such a noise in a truck that sat 15 years? It's a 1988 Comanche Pioneer, 5 speed manual, 4.0, 4x4, short bed Thanks, Evan

All good, Turned out the previous owner had the spark plugs gapped way too open. It fired up with the correct gap... ... but sounded real bad, like piston slap or something... ...I wonder if sitting for 15 years could drain the lifters enough to make a sound like that? And now that I said that, I wonder if it has hydraulic lifters?

So, did you ever solve the issue? Mine is doing something similar right now. 1988 Comanche 4x4 short bed 4.0 manual