Hey peeps, zj 96 4.0l limited
 

Guys I've got probs (lol) I'm not a mechanic, I ain't got a big garage with amazing tools neither. Lol
But! I love mi truck and she's poorly, and I AINT killing her off . So any help is greatly appreciated.
I initially had a O2 upstream code ,so I fixed that (got new sensor) but needed run her a cpl weeks before that to get to work, she ran pretty ruff.Then I put her in my garage to fix her up for mot.
Probs she has ,
1 - I found oil puddle in air box housing
2- I renewed all plugs and distributor cap/rotor and found pot4 plug was like it has never been firing (clean as a whistle) checked spark ,got spark to all 6, got another code come up for injector (code 27) so I got an injector on the way, but I also got a £20 compression test kit and (I don't know if I trust it or not) but it gave me 0psi on pot 4 , 75psi on the rest apart from pot 1 50psi.which I know are all well under .
I've always thought I had a coolant loss since I bought her 1.5 yrs ago.(topping up prob every cpl months or less)
She has white smoke(not too bad) but it's there. She will start fine ,pull fine up and down the back of mi house.
But I'm needing to find out why pot 4 says no psi and isn't firing and why I have the oil in the air filter housing ?
I've taken rocker cover off and everythings clean as a whistle and all tapping away nice and quiet? Oh I do have a slight bit of white stuff in the top of my rad ,no bubbles tho when on tick over .
I'm thinking head gasket, but would that give 0psi in only pot 4 ? Maybe a stuck valve? I had it ticking over with plug 4 out and i can hear what sounds like massive compression coming from the hole ? I'm lost

Welcome, Eth. :cheers:

Bad news: If those numbers are accurate, your engine is toast. :( I don't know how it's even running. I think your first two moves are:

1. Stop buying parts.
2. Get those compression numbers checked by a shop.

Thanks for your reply
 

I decided wip the head off , 5-8mm hole in the middle of pot 4 . (Duno how that happened)lol sumps coming off ,Gona save up get a new lot a pistons /rings/ bearings . That'll do the trick 😁. Got a micrometer in post to see if I can go up .30 or something on the pistons . This is all new to me, but I'm enjoying doin it ,coz I LOVE MI BEAST !!!!! 😎😎😁

Usually detonation (pinging) causes holes to burn in pistons. It takes a long time to actually create a hole though. A lean condition can cause it, like a bad injector.

I don't know why everybody wants to go .030 over when .010 would probably do it. You won't gain hardly any extra power with a .030 overbore. Not enough to notice anyway.

Zj
 

Hy thanks for that mate, .10 it is lol, and also thanks for the explanation on the piston hole , because i DID have a code for injector prob ,but alas I fixed it too late 😁 lol

Sometimes it depends on what pistons you can get. Less than .030 oversize are sometimes harder to find for certain engines. My thought was if a later rebuild is necessary, if it's already .030 over, you're screwed.