Hey guys. I bought a 2002 ram 1500 with the 5.9, 4x4, 132k verified by carfax. It is a nice truck, but I noticed since purchase that it had a slow acceleration problem. I am 95 percent sure it's the cats, but I also wanted to do a compression test just to see the health of the motor. And I was doing plugs and wires anyway because they were looking bad. Anyways, the results are as follows.

cyl 1 - 110
cyl 2 - 90
Cyl 3 - 120
Cyl 4 - 110
Cyl 5 - 100
Cyl 6 - 100
Cyl 7 - 110
Cyl 8 - 120

I did this test with all spark plugs out, not a super warm engine, and i did not flood the gas pedal when doing it, which some people online say that you should, but I'm not sure it matters that much. Spark plugs were white on the end on every single one.. Anyways, it looks like generally low compression across the board, and one cylinder is only at 90 psi...
so what do you think this means as far as the health of the motor? if only one cylinder was low I'd feel better about fixing it, but with all of them being low I feel like that points to a new motor.... but how low is too low? The truck runs fine other than it feeling like it has half the power it should, and is only noticed above 3k rpms, again, I think its the cats. There are no check engine lights on and everything else seems to work like normal.... im not very well versed in engine work but am mechanically inclined. I know I should have done a wet test and maybe still will, but I genuinely didn't think it would have bad compression. Just trying to figure out if I should look for a new truck or not, because I dont see it being worth fixing if it does need a new engine...
thanks for any input!

Edit: i probably didn't number the cylinders correctly, but the one with 90 psi is the front drivers side cylinder, if it helps. One of my buddies said it could be a head gasket but I dont see any noticeable coolant in oil... thoughts?

 

Yeah, your numbers suck. That's not going to be a head gasket problem. Might wanna retest, with the throttle wide open. The engine needs air in the cylinders to compress to get an accurate number. Clogging cats could also affect the numbers, so, might wanna pull the front O2 sensors as well. If the numbers come up significantly, replace the cat. Timing chain may also lower the numbers, but, given what you have there, I would be more likely to suspect rings.....

Front cylinder on drivers side is #1, odd on drivers side, even on passenger side. Front to back drivers side is 1, 3, 5, and 7. Passenger side is 2, 4, 6, 8.

 

Probably blown plenum led to clogged cat which led to cracked heads, which also leads to cat fragments getting back pressured into engine and scarring up some items would be my guess because the 5.9 when taken care of it’s pretty bulletproof