FJ62 high idle back with a vengeance. Update, new mystery, 2nd update. (1 Viewer)

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Saucerman

Saucerman

Joined
Apr 10, 2017
Threads
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Location
Deep South, Powder Springs GA
De-smogged and have had high idle ever since.
Changed the fuel pressure regulator, and fuel damper with the de-smog.
Cleaned the TPS 3 weeks or so back and managed to get the truck to idle as it should for 3 whole weeks.
Today coming home from a hike I noticed the idle claiming higher and higher. At a stop light or intersection I could blip the throttle and it would idle back down to normal, but every time I came to a stop the idle was at 1200-1800.
I had ordered a new TPS. I installed this and never could get it to test our matching the ohms in the FSM. So I installed it as close to the original position that I could.
Idle now at 1000-1100. Not coming down no matter how much adjustment.
FWIW I could never get the IAC to match the FSM ohms either. Maybe look at IAC now?
 
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My 60 did that a few times while I was driving and in gear. I would accelerate and then let off the gas and it would keep climbing and speed up until it almost red lined. Slam on the brakes and it stopped. After the 3rd or 4th time it happened I figured out it was the throttle cable. A few strands of the core cable had frayed and were catching just inside the outer housing causing the throttle cable to pull itself forward as if I was stepping on the gas. Not sure how the 62 is linked up. Have you looked at that? Could simply be coincidence that it started with the desmog.
 
Cable is good too. I was hoping that too. That would be a relatively easy fix. No luck there though! Thanks for checking in.
 
cps432 said:
My 60 did that a few times while I was driving and in gear. I would accelerate and then let off the gas and it would keep climbing and speed up until it almost red lined. Slam on the brakes and it stopped. After the 3rd or 4th time it happened I figured out it was the throttle cable. A few strands of the core cable had frayed and were catching just inside the outer housing causing the throttle cable to pull itself forward as if I was stepping on the gas. Not sure how the 62 is linked up. Have you looked at that? Could simply be coincidence that it started with the desmog.
Click to expand...
Cable on a 60 you must have a weber carb or something aftermarket 62 has a cable 60 is all mechanical linkage grom factory
 
I don't think so. Tried everywhere and got nothing. Plus vacuum leaks usually can't be corrected by throttle blips. If it is the ISCV the truck is toast because they are not available any longer. I tried to listen while my wife cycled the key on and off and I couldn't hear a thing coming from that valve.
 
You could try cleaning the iscv . A mud member may have a spare for sale?
Having a spare valve sounds like a pretty good idea now that they are obsolete.
 
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tmxmotorsports said:
Cable on a 60 you must have a weber carb or something aftermarket 62 has a cable 60 is all mechanical linkage grom factory
Click to expand...
It’s stock. I was mistaken. It’s the choke cable that was causing my problem. It was intermittent at first and then became constant until I fixed it.
 
tmxmotorsports said:
Cable on a 60 you must have a weber carb or something aftermarket 62 has a cable 60 is all mechanical linkage grom factory
Click to expand...

it’s a 62 isn’t it? Which I believe run throttle cables instead of a linkage.

@Saucerman id check for vacuum leaks again.
 
No vacuum leaks I could find. Is there another way to check for leaks say other than the propane torch method? I can't imagine why a leak would suddenly develop that could be solved by hitting the throttle. But I will try again.
 
Saucerman said:
No vacuum leaks I could find. Is there another way to check for leaks say other than the propane torch method? I can't imagine why a leak would suddenly develop that could be solved by hitting the throttle. But I will try again.
Click to expand...
Propane is the best method IMO. Maybe I missed it…but did you pull the actual throttle body off and make sure the plate isn’t sticking somewhere in its rotation?
 
I did, but not since this latest incident. I will do that again this week for sure. I need to take out stock in TB gaskets. This is one of those frustrating things to try and chase down.
 
Yeah for sure. Idle issues can be a real pain especially on these older efi systems. TPS, IAC, vacuum leaks, timing, bad ground, low voltage, temp sensor going off. All things I can think of and relatively in order of most to least likely.

checking your grounds is a good thing to do actually. Efi sensors like to have steady clean voltage. Low voltage can effectively shift the scale…though most work on 0-5 volts iirc. Still a low voltage could cause headaches. This could be a result from a dirty/corroded ground wire or plug connector somewhere
 
Saucerman said:
I did, but not since this latest incident. I will do that again this week for sure. I need to take out stock in TB gaskets. This is one of those frustrating things to try and chase down.
Click to expand...

Smear a very thin layer of grease or sylglide on the TB gasket so that you can pull the TB without wreaking the gasket.
 
Saucerman said:
No vacuum leaks I could find. Is there another way to check for leaks say other than the propane torch method? I can't imagine why a leak would suddenly develop that could be solved by hitting the throttle. But I will try again.
Click to expand...

Doubt it's a vacuum leak. In my experience a vacuum leak on a 3FE results in low idle. For example if you pull the oil cap on the valve cover while the engine is running it will set up a vacuum leak that will really make the engine stumble.
 
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