Bad News: Low compression in cylinder #1

I was @ my dad's house Sunday, to replace my coil springs as they are shot. I soon found out that my passenger side spring perch is completely rusted out & barely there.

If that weren't bad enough, my dad said it sounded like I had a dead cylinder. I pulled the plugs & they all looked fine, however, when we did a compression check, 2-6 had 140-150#'s of compression & cylinder # 1 had 80#'s.

SON OF A B****......

My motor has 119,000 miles & is a 4.0. When I bought it, it had sat for nearly 4 years with less than 1000, maybe less than 500 miles on it a year.

I have yet to remove the valve cover to check anything out. I'm inexperienced to say the least.

Fast forward to tonight, I was on my way home. I'd probably driven 15 miles when my Check engine light came on. My Maintenance Required light has been on for awhile do to something else. I turned off the road & came to a stop, the engine stalled out & the "oil" dummy light was lit up. I popped the hood to take a look.

It seemed like the valve cover over the low #1 cylinder was surprisingly cool. I started it back up & drove another 3 miles home. The light did not come back on & when I got home & popped the hood, the valve cover over the #1 cylinder was now warm.

Any ideas what it could be or what I should check?

Sorry for the windy post, any help is appreciated..

Blowing sunshine--maybe you have a carbon encrusted valve. Maybe some blew off enough for the valve to close and get enough compression to start firing.

Dump a can of MCCC or Seafoam through it--miracle in a can?

I'm glad you're around Joe. You seem like one of the few that responds to my posts.

I was actually thinking about that on the way home when the "Check Engine Light" popped on. Hell I may run back into town just to get some now.

I actually put some in before but ran it for like 10 minutes because it started smoking a little out of the front CCV valve elbow.

+1 on the Seafoam.

You could have had a stuck lifter or a stuck valve as Joe said that would cause low compression in the #1 cylinder. Hopefully that's all it is, otherwise you need to look into head gaskets and cracks in the head.

What year is your jeep? The 2000-2001 XJ's are notorious for cracked heads.

Personally I recommend BG44K.

old_man said:

Personally I recommend BG44K.

Click to expand...

BG44K is my ABSOLUTE favorite for cleaning the fuel injection system, but MCCC or Seafoam seems to do a better job on cutting carbon when added through the brake booster vacuum line, IMHO.

Should I add Seafoam directly into the oil or through the brake booster vacuum line? Which vacuum line is it?

Large black line attached to the brake booster.

Stick a small funnel in the end, follow the directions.

Note: things are going to get a little SMOKY, so don't do it where people are going to be objecting--strenuously--to the smoke cloud.

I just bought some Seafoam. I let it suck some of it into the break booster line, the rest into the oil fill & finally a little into the gas tank. I may be crazy, but, I would swear that it "sounds" like the compression is up on the 1st cylinder. I don't even know if it can work that quickly, but, it definitely sounds better upon crank up.

I'll check compression tomorrow then try to leak down test.