Interesting Compression Test Results...

[Toms01PSD]

So guys. I decided to do a compression test for shits and giggles today on my 99 3.slow with 181,xxx miles on it. Cylinders 1,2,3 are on the drivers side starting at the radiator and back towards the firewall, same for 4,5,6 on the passenger. Tell me what you think!
#1:149
#2:140
#3:121
#4:170
#5:152
#6:152

 

[RumpRanger98]

i have cylinder 1 and 3 at 120 and im getting a cel for misfire on cylinder 1. other than that the rest are 150.
Im still not sure if im misfiring due to low compression and/or whats giving me the low compression on those 2.


So I would be a little concerned with the #3 cylinder, not sure if its causing you to misfire and throwing a cel or not. also the #4 is just a tad high, not sure what problem if any this would create. ill shut up and let the pro's respond

 

[Toms01PSD]

lol, nah it's ok. I'm not an expert, any input is helpful. I just can't figure out why #3 is so low.

 

[RumpRanger98]

lol, nah it's ok. I'm not an expert, any input is helpful. I just can't figure out why #3 is so low.

being im not an internal motor expert and never mess with stuff inside the engine. Im having my cousing take the valve cover off and look at my #1 and #3 cylinders both reading at 120. He is suggesting maybe a bad valve spring(s). I think its either that or there is tiny crack in head gasket or tiny crack in heads.

from what im told either of those things could cause low compression. Ill let you know what i find out about mine running low. Im sure theres a few other possibilites for low compression other than crack head or gasket. Someone will chime in soon.

 

[WNY964x4]

lol, nah it's ok. I'm not an expert, any input is helpful. I just can't figure out why #3 is so low.

it could be a bad valve seal , piston rings , carbon buildup ont the valve seats , or the plug is not seated completely , the lowest pressure should be within 75% of the highest

 

[04 EDGE]

cylinder 1 on fords is always on the right or passenger side.

looks like you have a problem in cylinder #6

 

[shadetree]

cylinder 1 on fords is always on the right or passenger side.

looks like you have a problem in cylinder #6

Correct, and valve seals, guides, etc., won't cause a compression problem. Compression is read when the cylinder is sealed. You either have a leaking valve, rings, or head gasket.shady

 

[beejium]

Correct, and valve seals, guides, etc., won't cause a compression problem. Compression is read when the cylinder is sealed. You either have a leaking valve, rings, or head gasket.shady

on the money Shady. i also wanted to point out that most manufacturers allow a 10% curve in compression between cylinders.

 

[skippy]

lol, nah it's ok. I'm not an expert, any input is helpful. I just can't figure out why #3 is so low.

Throw a couple Squirts of oil in there and check it again.

 

[Toms01PSD]

cylinder 1 on fords is always on the right or passenger side.

looks like you have a problem in cylinder #6

I understand that. I posted it the way I did so that regardless of whatever is REALLY cylinder #1 everyone would be in the same boat and understand what the hell I was talking about. BTW, my sister could have told me I had a problem in #6.

 

[Toms01PSD]

Throw a couple Squirts of oil in there and check it again.

To everyone else, thanks for the tips. I'm not much for internals but I replaced the head gaskets at 175k or so. I understand that by squirting some oil in there it will tell me whether I have bad valves or bad rings. Correct? Overall, what do you guys think about the other readings I got? Keep in mind that it has 181k. I'm going to drive her til she dies though, she doesn't wanna give in.

 

[skippy]

To everyone else, thanks for the tips. I'm not much for internals but I replaced the head gaskets at 175k or so. I understand that by squirting some oil in there it will tell me whether I have bad valves or bad rings. Correct? Overall, what do you guys think about the other readings I got? Keep in mind that it has 181k. I'm going to drive her til she dies though, she doesn't wanna give in.

If a couple or three squirts raises compression,probably rings.If it stays low probably valves or head gasket.

 

[RumpRanger98]

Throw a couple Squirts of oil in there and check it again.

doing this and if it changes compression, indicates the rings are to blame right?

for some reason the post above this just showed up, disregard this haha

 

[Toms01PSD]

If a couple or three squirts raises compression,probably rings.If it stays low probably valves or head gasket.

Hmm, I hope it's valves or rings, I just did head gaskets. Also, I seem to have a lifter tap, atleast what it sounds like from the same cylinder.

 

[Beef52751]

for 181,xxx miles i would be happy with the results. your cylinder walls are probally begining to taper, rings wearing out, valve seats getting leaky, etc. if anything hope its not the rings or cylinders. valves are easy to replace compared to rebuilding the whole motor.
Beef