Boss_Hotrod

I just finished doing a compression test on my 93 5.0. I did it because my brother says it feels like its weaker than it used to be. Here are teh results I got. I did the test with all plugs removed, fuel disabled, spark disabled, and using the ignition switch to spin the starter. Thats they way my service manual said to do it only I didnt open the throttle body up (did have the intake pipe off though so I could reach the plugs).

1-140 psi
2-120
3-130
4-125
5-130
6-125
7-130
8-120

Do those numbers look okay? I thought they were a little low but Ive never done a compression test.

mjr46

a few on the low side but none the less the car should still run okay.. 100 psi is the bare min for complete cumbustion to take place as a general rule of thumb

Boss_Hotrod

OKay. Thats good. I dont have the money right now to rebuild it.

One question why would it burn a lot of oil? My cousin said it might be valve stem seals. Anything else?

mjr46

could be alot of reason why it burns oil......worn valve guides, bad seals, gummed up oil control rings, wear on the cylinder bores creating excess skirt to wall clearance....how many miles on the motor/? also depends on how well car was taken care of/ maintained....pcv system may have a prob too

93 LX FiveO

my old fox had those #'s and ran 14.1 on the 170k nonrebuilt engine

highest cylinder had 128 psi

Boss_Hotrod

I have no idea how many miles are on it. One of the previous owners put in a 3.73 gear and didnt change the speedo gear. I think the car has been drag raced in its past. I beat the crap out of it since its only a toy. I replaced the pcv valve about a year ago hoping that would help some but it didnt.

Lysawy

Little on the low side ...

what you need is numbers to be close to each other for instance my were between 155 psi and 145 consistant warm engine that is.. 115k .

mjr46

keep beating on it until it goes then..and how much oil is it using??

Boss_Hotrod

I dont know how much it uses. We just check it everytime we get ti out and if it needs some we just top it off. The last Time I changed the oil I got about 4 quarts out of it But I dont know how much was in it before I changed it.

FLcracker9

I'm assuming you performed a "dry" compression test. Try doing a "wet" test. Same procedeure, but squirt about a tablespoon of oil in the spark plug hole before each reading (and yes, you should have the throttle wide open). If compression goes up considerably, you have a ring issue, if compression doesn't go up, check the seals, then guides.