Bad idle - 1970 FJ40, 1F Engine, Stock Carburetor (1 Viewer)

[nachohouse]

I'm stoked to be the new owner of a '70 FJ40 and this forum has been an incredible resource! I've found all the knowledge on here to be extremely helpful. I'll try to provide all the relevant info I've got, so go easy on this noob.

Purchased the vehicle a couple of months ago and it ran excellent for the first few drives (including a 45-60 min cruise home from the place I bought it). The PO had the vehicle living outside and the it was used sporadically for short trips. PO informed me when I purchased that the carb was recently rebuilt & tuned, including a new idle solenoid.

After I got the cruiser home, before replacing the battery with a red top Optima, I had some wonky electrical stuff happening (horn stuck on, headlights working intermittently, etc.) that resolved after cleaning up some corrosion on the fuse panel. Last time I checked, I did hear an audible "click" when turning the ignition—confirming functioning idle solenoid? I refueled the cruiser to at least 3/4 tank with 91 octane (old habit from being a former BMW owner, I'm going to burn the cheap stuff in the future).

Since that refuel, the car is not happy idling. It won't hold an idle without at least half-choke, otherwise the engine seems to lean out and die. The idle mixture screw does not seem to do anything to alter the idling characteristics either (tried turning it full-out and full-in with no effect). The fuel filter seems free of any major visible debris.

I'm about to run some Seafoam through the tank and the carb to see if I can de-gunk things before attempting a rebuild—seems like people have had some luck with Seafoam on here. Are there other areas I should be looking at or things I am missing? Does it just hate my 91 octane? Did I agitate years of crud in the tank on that refuel? Drain the fuel tank and start fresh? Is there magic spot I should be targeting with some Seafoam/carb cleaner?

Thanks for all the help!

 

[bhsdriller]

Idling with only choke sounds like a vacuum leak as well

I wouldn't try to de-gunk the tank while running it through the carb/system it'll just cause more problems. If the tank and lines are dirty they need to be cleaned out. New tanks are still available

 

[nachohouse]

Idling with only choke sounds like a vacuum leak as well

I wouldn't try to de-gunk the tank while running it through the carb/system it'll just cause more problems. If the tank and lines are dirty they need to be cleaned out. New tanks are still available

Thanks for the reply!

Are there common culprits of a vacuum leak? Had a mechanic buddy hook up a vacuum gauge and he said it was making good vacuum (don't know the reading but I can report back).

What's the best way to get a look inside the tank? Remove the sending unit and look down inside? Any other advice for flushing the fuel lines would be appreciated also! Thanks again.

 

[Chungas Revenge]

Electrical Gremlin infestation. Loathsome little buggers. Per ^^^ check for vacuum leaks in and around your carb w/brake cleaner (check YouTube). Might want to start at your dizzy and check the cap, points, wires and plugs just to rule out foul play on that side of the engine block. Check your fuel filter while your over there, that may give you some insight to what’s lurking in your petrol tank.

 

[Green Bean]

If I'm not mistaken, just because you hear an audible click, does not necessarily mean that the solenoid on the carb is working properly. The symptoms described are similar to an inoperative solenoid. Might want to ping @ToyotaMatt

 

[63cruiser]

Picks of said truck. Not many of us in the area.

 

[BloodyMGT]

I'm stoked to be the new owner of a '70 FJ40 and this forum has been an incredible resource! I've found all the knowledge on here to be extremely helpful. I'll try to provide all the relevant info I've got, so go easy on this noob.

Purchased the vehicle a couple of months ago and it ran excellent for the first few drives (including a 45-60 min cruise home from the place I bought it). The PO had the vehicle living outside and the it was used sporadically for short trips. PO informed me when I purchased that the carb was recently rebuilt & tuned, including a new idle solenoid.

After I got the cruiser home, before replacing the battery with a red top Optima, I had some wonky electrical stuff happening (horn stuck on, headlights working intermittently, etc.) that resolved after cleaning up some corrosion on the fuse panel. Last time I checked, I did hear an audible "click" when turning the ignition—confirming functioning idle solenoid? I refueled the cruiser to at least 3/4 tank with 91 octane (old habit from being a former BMW owner, I'm going to burn the cheap stuff in the future).

Since that refuel, the car is not happy idling. It won't hold an idle without at least half-choke, otherwise the engine seems to lean out and die. The idle mixture screw does not seem to do anything to alter the idling characteristics either (tried turning it full-out and full-in with no effect). The fuel filter seems free of any major visible debris.

I'm about to run some Seafoam through the tank and the carb to see if I can de-gunk things before attempting a rebuild—seems like people have had some luck with Seafoam on here. Are there other areas I should be looking at or things I am missing? Does it just hate my 91 octane? Did I agitate years of crud in the tank on that refuel? Drain the fuel tank and start fresh? Is there magic spot I should be targeting with some Seafoam/carb cleaner?

Thanks for all the help!

Agreed.
Sounds like an intake/vacuum leak.
Start with easiest and cheapest fixes.
Replace or remove air filter.
Check carburettor to manifold bolt torque.
Check intake/exhaust manifold to head bolt torque.
Plug vacuum hoses to brakes, PCV valve, distributor and choke diaphragms.
Check compression on each cylinder (burnt intake valve).
Remove and measure/flatten intake/exhaust manifold surfaces. I use a 24" belt sander.
Replace intake/exhaust manifold gasket.
Clean and rebuild carburettor. I use an ultrasonic cleaner and Simple Green 1st, then Berryman Chemdip followed by hot water rinse.

 

[nachohouse]

Back with an update—thanks for all the replies and advice. Hopefully there are breadcrumbs here for a future 40 owner with idling troubles.

I've done a ton of work to the cruiser since the last post. The idle solenoid was indeed disconnected, and I believe the carb was tuned to quasi-idle without the solenoid. I reconnected and tweaked the idle speed/idle mix screws and checked timing (was way too advanced)—the rig starts, idles and runs great now!

I also replaced the gas tank with a new one from CCOT. The old tank had tons of old fiberglass patchwork from a PO and some gunk in the bottom of the tank. After a new tank, carb tune, and fresh gas, we're back to being semi-roadworthy.

Next project is a fuel leak I've got from the bottom of the pump. Just ordered a new one from @ToyotaMatt—looking forward to getting that installed when it comes.