84 FJ60 with desmogged 2F intermittent dying (1 Viewer)

[Spears41]

I have an 84 FJ60 with rebuilt OEM carb and desmogged 2F motor with 174k. Just had the head rebuilt and new gaskets respectively due to a coolant leak into cylinders 3&4. Motor runs better than ever, doesn’t leak any oil. When I first got it back from the shop, vacuum would be anywhere from 16 to 21 for unclear reasons, but peaked at 21 when warm. I’ve had intermittent dying issues at idle happening 1x a week for the last month since picking it up. I’ll back off the throttle to decelerate and shift down and it will fail to idle and drop RPMS until it dies. I can always overcome this with more throttle or with the choke pulled out. It self resolves after a minute or two and I’m back at idle with no issue. I can tell it’s time to push the choke back in because the idle will shoot back up, usually after oscillating between 1200 and 1800 rpms rhythmically for no apparent reason. Any ideas on what’s causing this?

I just sent off my spare carb for a rebuild by Jim. Hoping I chose the right thing to do after pouring over the carb diagrams and thinking I might have an idle circuit issue.

 

[4runner2FJ60]

I think there are a few things it could be. Is the pcv valve new or working?

 

[Spears41]

I think there are a few things it could be. Is the pcv valve new or working?

No idea if it works but it’s not new. I’ll look into how to test it.

 

[Seth S]

Check for vacuum leaks.

 

[mattressking]

How desmogged is desmogged? Post up a few pictures of the motor, preferably around the carb/manifold. Desmogged could be barebones or it could have a few bvsv's/vsv/vtvs left. If you aren't the mechanic, make sure someone that is fiddling with the truck understands 60s well, otherwise they will bandaid issues with incorrect timing or poor mixture adjustment.

Things to note:

1. Make sure timing is at 7* with hoses removed vacuum advance, at idle and idles under 950rpms. hot or cold. Ideally less than 750rpms at idle. With a refreshed top end, you should be idling smooth at 650.
2. Make sure you swapped ported vacuum from carb to the HAC port on vacuum advance unless you have a recurved distributor.
3. Make sure both canisters hold vacuum up to 22inHg for 1 minute.
4. Make sure vacuum lines (or what remains) are routed correctly. (see massive desmog thread).
5. Once timing is verified, all vacuum hoses are plugged back in, read vacuum like @Seth S said. If the engine is cold, make a note of reading. If its hot, make a note of the reading. If its bouncing with 1-2" of fluctuation, check valve lash.
6. Once valve lash is verified, check vacuum, hot and cold at idle. If its low cold and high hot, something is leaking when cold (duh). Could be bvsv related, could be manifold related, could be incorrectly routed vac lines, many many things, including carb screw up during rebuild.
7. Verify no leaks at manifold by spraying carb cleaner/ether/similar at the manifold/head surface, listen for fluctuation when spraying.
8. Verify your plugs are gapped correctly (.032).
9. Make sure your mixture is set correctly. Perform lean drop and watch vacuum gauge/rpms for best idle.
10. Report back.

 

[Spears41]

Thanks guys. I am going to dig in deep this weekend to start knocking out @mattressking 's list out on Saturday, working until then. The mechanic i've been using specializes in cruisers, but I don't know how far that goes (when I picked up the truck after the top end refresh, he didn't know where a few of my desmogged vacuum hoses went). When I desmogged it, I did it in accordance with the Jim C diagrams on here, including the HAC delete due to a massive EGR air leak.

In the meantime, I did have time to check the PCV valve and it seems pretty loose, maybe 0.5 cm of play side to side. I ordered a new gasket and PCV, hopefully be here in the next day or so. At least that will remove one variable.

It currently idles at 750 cold, 950 warm.

I'll snag some pictures ASAP.

 

[4runner2FJ60]

You might be able to use the pcv valve, check for function and or clean it out? You should be able to blow air thru the bottom out the top manifold marked side. You should not be able to blow air the opposite way. You can also tip it back and forth and see if the ball/valve moves back and forth inside. The PCV Grommet will definitely need to be replaced, not sure if it is even possible to save one on removal, just try to get all of it when you go for it (ie don't let parts of it fall down the hole!)

this may not fix your issues as listed above.