FJ40 2F Engine Idle Issue, not the usual fix, ideas?

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Mapleton, UT
Hello and thank you for all the knowledge that’s shared here!

We have an engine idle problem that has my son and I stumped:

Our ’82 FJ40, all stock original, with emissions, etc., had some oil leaks so we decided to embark on a father-son project and completely rebuild the 2F engine and re-seal the transmission and transfer case.

Our FJ has 123,000 miles on it.

When we started out, there were no issues other than the leaks.

After the rebuild, which included rebuilding the Aisin carburetor, it ran just fine.
After our third short outing of less than 12 miles, the engine would no longer idle. It did fine at higher speeds and would start right up if the throttle was partially open.

After reviewing the thorough information found here, we replaced the fuel cutoff on the carburetor (also making sure it actually ‘clicked’ when energized. No change.

So far, we’ve:

  • Verified ignition timing (several times).
  • Spark plugs look fine, maybe slightly damp.
  • Checked compression (still good and even across cylinders).
  • Went through the carburetor two more times.
  • Replaced the fuel.
  • Replaced the fuel pump.
  • Verified all vacuum tubes are correct
  • Pulled the manifolds and replaced the gaskets.
  • Used propane coming from a tube and introduced different areas to see if the engine speed changed (to check for vacuum leaks), with no difference noted.
It does run better when fully choked, but sill won’t idle below around 1200rpm.

Any ideas or suggestions would be greatly appreciated as we’re out ideas.

Many thanks!
Hello and thank you for all the knowledge that’s shared here!

We have an engine idle problem that has my son and I stumped:

Our ’82 FJ40, all stock original, with emissions, etc., had some oil leaks so we decided to embark on a father-son project and completely rebuild the 2F engine and re-seal the transmission and transfer case.

Our FJ has 123,000 miles on it.

When we started out, there were no issues other than the leaks.

After the rebuild, which included rebuilding the Aisin carburetor, it ran just fine.

After our third short outing of less than 12 miles, the engine would no longer idle. It did fine at higher speeds and would start right up if the throttle was partially open.

After reviewing the thorough information found here, we replaced the fuel cutoff on the carburetor (also making sure it actually ‘clicked’ when energized. No change.

So far, we’ve:

  • Verified ignition timing (several times).
  • Spark plugs look fine, maybe slightly damp.
  • Checked compression (still good and even across cylinders).
  • Went through the carburetor two more times.
  • Replaced the idle fuel cutoff solenoid
  • Replaced the fuel (with fresh fuel).
  • Replaced the fuel pump.
  • Replaced the PCV, made sure it worked.
  • Verified all vacuum tubes are correctly routed.
  • Pulled the manifolds and replaced the gaskets.
  • Used propane coming from a tube and introduced it to areas to see if the engine speed changed (to check for vacuum leaks), with no difference noted.
It does run better when fully choked, but sill won’t idle below around 1200rpm.

Any suggestions would be greatly appreciated as we’re out ideas.

Many thanks!
 
Joined
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Messages
641
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Lakewood, WA
Mine did the same thing when the idle solenoid suddenly died. Not sure if that is the same as the fuel cut-off on your 82. Sure wasn't fun to drive like that. I believe a new one was only $15, hopefully that's it. Not very often something is that inexpensive for a 40 fix! Good luck!
 
Joined
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Messages
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Location
Mapleton, UT
Mine did the same thing when the idle solenoid suddenly died. Not sure if that is the same as the fuel cut-off on your 82. Sure wasn't fun to drive like that. I believe a new one was only $15, hopefully that's it. Not very often something is that inexpensive for a 40 fix! Good luck!
Thank you, we replaced the idle solenoid once, I'm wondering if we got a bad one. It does click when energized, but maybe there's still an problem.
 

micruz60

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May be a good idea to run monofilament fishing line thru the same circuits that B y r o n mentions, if you can't tell the air is passing thru.
 

1911

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Thank you, we replaced the idle solenoid once, I'm wondering if we got a bad one. It does click when energized, but maybe there's still an problem.

The fuel cutoff solenoid is controlled by the "emissions computer", a circuit board on the firewall, inside the cab, under the dash. The cable connections on these are cold-soldered and known to crack, resulting in intermittent or zero operation. You can test this by bypassing the computer; run a 12-volt jumper wire straight from the battery to the solenoid. If it runs good that way, your computer is bad. If it is bad, you can permanently bypass it by identifying the wire from the solenoid to the computer, and grounding that.
 
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In addition to blocked idle passages, it could be an air leak as well if you're able to keep it running with extra choke. Can you post a pic or two of the carb as it sits so we can if there's anything obvious?
 
Joined
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Messages
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Mapleton, UT
The fuel cutoff solenoid is controlled by the "emissions computer", a circuit board on the firewall, inside the cab, under the dash. The cable connections on these are cold-soldered and known to crack, resulting in intermittent or zero operation. You can test this by bypassing the computer; run a 12-volt jumper wire straight from the battery to the solenoid. If it runs good that way, your computer is bad. If it is bad, you can permanently bypass it by identifying the wire from the solenoid to the computer, and grounding that.
Thank you, I had read about that in a previous thread and checked for cracks on the board, no issues observed. I wound up using a volt meter to verify the solenoid had voltage when the engine was running, it seemed normal
 
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In addition to blocked idle passages, it could be an air leak as well if you're able to keep it running with extra choke. Can you post a pic or two of the carb as it sits so we can if there's anything obvious?
Sure, I'll take some photos and get them posted. Thank you everyone for your input on this, what a great community!
 
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Sure, I'll take some photos and get them posted. Thank you everyone for your input on this, what a great community!
Here are the photos, obviously some open vacuum tubes that are connected when the air cleaner is on.

IMG_0972.jpg


IMG_0973.jpg
 

Steamer

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Did you check the fuel level in the carb window when it's idling poorly? You mentioned wet spark plugs.
 
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Did you check the fuel level in the carb window when it's idling poorly? You mentioned wet spark plugs.
Thank you for asking, yes it’s about half way up the glass. Each time I went through the carburetor, I verified the float level. Also changed the needle and seat a second time, just in case the first one was defective. That was also why I replaced the electric fuel pump, just in case the old one was generating enough pressure to send fuel through the needle and seat. What’s so odd is how it idled perfectly, until a sudden change while driving it back home.
 

GatorPlater

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That really sounds like a piece of debris in the idle circuit or in the piston circuit. Check all those with mono or ait.
 

ToyotaMatt

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Thank you for asking, yes it’s about half way up the glass. Each time I went through the carburetor, I verified the float level. Also changed the needle and seat a second time, just in case the first one was defective. That was also why I replaced the electric fuel pump, just in case the old one was generating enough pressure to send fuel through the needle and seat. What’s so odd is how it idled perfectly, until a sudden change while driving it back home.


part # 21062-61060

you need to check this hard and confirm and verify the FCS fuel cut solenoid .......

this is the 2 wire update kit i offer will work on ANY 2F Carb 1/75-9/87 40 55 60

incudes the updated harness side water proof update connector and terminals too in UV rated OEM Green


let me know if i can further help

thanks

matt











1656975894016.png


1656975923105.png

1656975947281.png

1656975973962.png



1656975998277.png
 
Last edited:
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One thing these vehicles never came with is a vacuum gauge. I know you said you tried propane method but by having a gauge in you field of view when driving can say a lot. To me without one always kept me guessing.
 

ToyotaMatt

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Here are the photos, obviously some open vacuum tubes that are connected when the air cleaner is on.

@GatorPlater :)

i see ONLY 1 wire coming from your device side 21062-61060 fuel cut solenoid green connector ?


if you or a PO installed a single wire Varity or this wire has been severed ?

if im correct , this may be a smoking gun and eazy peezy to remedy with the correct replacement parts above i mention to confirm and verify first ?




IMG_0972.jpg
 
Last edited:

Engineer8000

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Thank you, I had read about that in a previous thread and checked for cracks on the board, no issues observed. I wound up using a volt meter to verify the solenoid had voltage when the engine was running, it seemed normal

Where did you check voltage?
That FCS wiring looks questionable as @ToyotaMatt points out.
Also what @1911 said is very true about the emissions computer, I've seen many with bad solder connections.
It is easy enough to run a hot wire from the battery to the FCS to check.
I can help with the emissions computer if needed, I have refurbished/bench tested (not just painted or cleaned up - really verified to work per the emissions manual) computers on the shelf.
 
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part # 21062-61060

you need to check this hard and confirm and verify the FCS fuel cut solenoid .......

this is the 2 wire update kit i offer will work on ANY 2F Carb 1/75-9/87 40 55 60

incudes the updated harness side water proof update connector and terminals too in UV rated OEM Green


let me know if i can further help

thanks

matt









View attachment 3050181

View attachment 3050183

View attachment 3050184
View attachment 3050185
View attachment 3050186


Thank you Matt, the replacement unit looked nearly identical (but with a different connector so required splicing), but I'm not opposed to changing it again. The old one did 'click' when energized, as does the replacement. It continues to be energized when running, confirmed by a voltmeter at the leads.
 

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