Alright, so its the end of 2025, which means its been a year (almost) since my 80 died, and 6 months since I started this thread. Let's do something about that! (to be fair, some weird logistics involving moving a shipping container have to happen before I can work on it, so motivation has been low)
So if you make it through all the details about to be provided and have any suggestions, a thank you in advance!
Here goes...
So in January 2025 (the 31st to be exact), I got the oil changed in my 80 by the mechanic that my parents have used and trusted for 15+ years. This might be irrelevant, but worth mentioning.
A week or 2 later (don't remember exactly) I drove the 80 1.5 hours for the weekend. Ran fine. Got in to drive home and ran fine. But about halfway home, it may have felt a little more sluggish than usual on a road that I have driven plenty of times, but could have easily been my mind or the wind. Stopped and filled up 20-30 minutes from home. Had gotten 12.21 MPG since last fill up, so really good for a FJ80, lol! Still running fine. Get into town, so 20 minutes of driving, and pull up to the first stop light and nearly dies, or so I thought. Horribly rough idle, sounds like when my alternator went bad and while driving and drained the battery. Didn't die, but seemed like it was going to. Also important to note that the valves make a racket, something they had never done in the past. And yes, I had a valve job done when I got it. EDIT, actually, maybe I didn't. I swear it was done, but I don't see it on any receipts.
So, what causes rough idle on 30+ year old LCs? Vacum leaks caused by old intake hoses! Sweet! ordered some of those and replaced both hoses and two others as well. No change. What on earth? While I was at it, I replaced the cheap K&N-style intake with a factory air box from
Ebay. With the air box installed, it wouldn't start or idle without additional throttle from me. Took it back off and sputtered/hesitated like before I had done anything. At this point I gave up and took it back to my mechanic, still thinking it was a simple fix, given the sudden emergence of the problem.
He ran a compression test and leak down test. He also adjusted the valves. Results are as follows:
Cyl. 1 40 dry/45 wet; 95% loss, crankcase/exhaust valve
Cyl. 2 40/44; 94% loss, crankcase/intake valve
Cyl. 3 120/125; 55% loss, exhaust valve
Cyl. 4 125/128; 45% loss, crankcase
Cyl. 5 120/120; 73% loss, crankcase
Cyl. 6 145/148; 40% loss, crankcase
Hmm...
First, I kind of think that he used 200 psi on the leak down test, which is more that a 3f-e is designed to hold, compression wise at least. 148 psi is in spec, so 40% loss doesn't seem right and 60% of 200 is 120, so not out of the realm of possibilities. Seems like a lot of pressure.
So, from a quick glance, the data says I need a rebuild, but wait a minute! This engine went from perfect to bad in 20 minutes? Is that possible for an engine with fresh oil to shred the rings in 20 miles? This vehicle wasn't very well documented and had been sitting for about 10 years with very little use, but still, 20 miles? on a vehicle with 180k miles? In my mind, it just doesn't add up
So I dove into Mud and started searching.
So, if it doesn't need a rebuild, what does it need?
I'm wondering if the HG bridge between cyl 1 and 2 is blown, causing the really low pressure in those cylinders. I'm also wondering if the cam gear has slipped, like
here.
Very slim probability of those happening at the same time, but I'm trying to find out what would just, boom!, go bad? Rings just don't seem like the answer, but if so, then I'll get to rebuild and engine
If you made it this far, thank you. If you have any ideas, thank you. If you need more information, I'll do my best. And if you have a solution, I might be a little slow, but I am open to suggestions.
