Random no Acceleration and a bucking bronco

Joined
Apr 25, 2014
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364
Location
Phoenix, Arizona
 
Hey guys,
My 85 FJ60 is having some issues...
I had put a brand new OEM Coil along with other upgrades into my rig last year...everything had been running fine until I had it in the shop recently for a few minor things. I got it back and it randomly starts sputtering and bucking...it will not let me accelerate without stomping on the pedal and riding the clutch to get going...(this happened in traffic) It lasted about 10 minutes and I got it back to the shop where it stopped doing it..Of course!
I left it there and got a call saying that the coil had blown....

Got that replaced, seemed to run fine for about 2 days, then it started doing it again...Then stopped, and started again...totally random. It will sometimes last a day or 2 or 15 minutes. Took it back in and coil was replaced (not blown this time) but it was then fine for a week.

It has now been doing it on and off for the past week...
MY check list/thoughts are this:

I have checked these things:
1. Fuel window in carb is half full
2. Fuel filter is brand new
3. Fuel pump is in great shape and has awesome pull.
4. Coil is not blown

Could it be any of these things? or what else should I check??

1. Distributor issue?
2. Fuel tank?
3. Fuel lines?
4. Plug wires?
5. Coil Regulator?
6. Amps to coil?


What am I missing??????
Thanks
 

NeverGiveUpYota

Dare me.
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Fuel cut solenoid, check that it’s working, the o-ring and make sure the emissions computer wasn’t unplugged.
If your coil was blown check your tach and coil wiring. Also could be the regulator on the diz is fried?
Those are just a few things that come up right away in my head.
 

Robert Franzke

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I would second the fuel cut Solenoid as @NeverGiveUpYota suggests. Could be any of the things @NeverGiveUpYota mentions but this happened to me exactly as you describe and it turned out to be the FCS. I would start there as its relatively easy to check and test and move on to the other stuff from there. How's it idle?

With my issue, if I gave it a lot of gas to get it going again, it most times would come back and run good. It was mostly when I was idling at stop lights I had the issue. Would a lot of times just shut off if coming to a stop from say highway speeds. But would also, while driving at highway speeds, buck like crazy. Felt like repeatedly hitting a wall while going 70. Nothing weird about that at all.

You can test if its the FCS case by shutting it down, turning on the key, and unplugging and plugging the FCS multiple times. Should hear a click when plugged in. I also, while my truck was running good, with the engine idling, would unplug the FCS to mimic what the engine would do when it was acting up. Acted exactly the same. Normally the FCS is grounded at the Emissions Computer and the computer controls its function based on input from a vacuum switch mounted on the driver side fender and switch the ground on and off as needed to energize the FCS. The way I understand it is basically the FCS is designed to stop the flow of fuel to the carb to prevent un-burned fuel from entering the exhaust when decelerating. My issue was the grounds on the PCB were worn and got cracked and brittle thus creating a bad ground there. Seemed for me to happen when temps changed enough to expand or contract the solder joints(really cold or really hot). I re-flowed solder on my PCB and its never done it since. You can also bypass the PCB and ground directly to the carb, but there are some negative side-effects of doing this long term. But you could do it as a test just to see if it eliminates your issue. Most of that is in the threads listed below.

Check the thread I started on my FCS issues here:


and this one which has some good info on the operation of how the FCS system works and what it does here:


HTH.
 

ToyotaMatt

Factory Focus-Point Mind-Set Aproach
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- u mentioned the Coil was replaced recently , Why ? in Detail


- also , what other ignition Parts where Changed or replaced

- were any Aftermarket Like a Pertronix Brand Igniter for Example ?




8762215154_2013443257.220x220.jpg
 
Joined
Apr 25, 2014
Messages
364
Location
Phoenix, Arizona
 
I would second the fuel cut Solenoid as @NeverGiveUpYota suggests. Could be any of the things @NeverGiveUpYota mentions but this happened to me exactly as you describe and it turned out to be the FCS. I would start there as its relatively easy to check and test and move on to the other stuff from there. How's it idle?

With my issue, if I gave it a lot of gas to get it going again, it most times would come back and run good. It was mostly when I was idling at stop lights I had the issue. Would a lot of times just shut off if coming to a stop from say highway speeds. But would also, while driving at highway speeds, buck like crazy. Felt like repeatedly hitting a wall while going 70. Nothing weird about that at all.

You can test if its the FCS case by shutting it down, turning on the key, and unplugging and plugging the FCS multiple times. Should hear a click when plugged in. I also, while my truck was running good, with the engine idling, would unplug the FCS to mimic what the engine would do when it was acting up. Acted exactly the same. Normally the FCS is grounded at the Emissions Computer and the computer controls its function based on input from a vacuum switch mounted on the driver side fender and switch the ground on and off as needed to energize the FCS. The way I understand it is basically the FCS is designed to stop the flow of fuel to the carb to prevent un-burned fuel from entering the exhaust when decelerating. My issue was the grounds on the PCB were worn and got cracked and brittle thus creating a bad ground there. Seemed for me to happen when temps changed enough to expand or contract the solder joints(really cold or really hot). I re-flowed solder on my PCB and its never done it since. You can also bypass the PCB and ground directly to the carb, but there are some negative side-effects of doing this long term. But you could do it as a test just to see if it eliminates your issue. Most of that is in the threads listed below.

Check the thread I started on my FCS issues here:


and this one which has some good info on the operation of how the FCS system works and what it does here:


HTH.
I’ll check this out!
The idle is fighting... it barely stays at...say 500 rpm sputters and fights..
Your description of the highway speeds is accurate... thanks for the links, I’ll dig in!
 
Joined
Apr 25, 2014
Messages
364
Location
Phoenix, Arizona
 
- u mentioned the Coil was replaced recently , Why ? in Detail


- also , what other ignition Parts where Changed or replaced

- were any Aftermarket Like a Pertronix Brand Igniter for Example ?




Coil was replaced as the shop said it Blew up.
Only other thing replaced was the starter.
Have not had any issues with it...

Thoughts??
 

g-man

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Sep 5, 2006
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Location
Charlottesville VA
 
 
stalling at idle and hesitation on acceleration are, as mentioned above, signs of a non functioning fuel cut solenoid. Have someone stand next to the carb and turn the key, you should hear a click. You can also unplug the wires and run jumpers to it from the battery to verify the "click".

You could have a massive vacuum leak, easy to tell from the "sucking sound" coming off the intake or vacuum lines. Spray carb cleaner around the intake, base of carb to check for leaks.

timing could be way of if someone bumped the dizzy.
 
Joined
Apr 25, 2014
Messages
364
Location
Phoenix, Arizona
 
Thanks! as you are all pointing me in that direction, I will give it a shot.
If the selonoid is in fact bad...where can I get one? anyone have thoughts there?
 

Robert Franzke

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Messages
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Plano Texas
Most likely it is just not connected. Maybe a loose connection or broken wire.
I would also say your ICS is most likely fine. While its possible the ICS could go bad after 30 years, the good news is that they are simple and don't do much, so its unlikely its bad. As @g-man says its probably just poor grounds, or bad wiring. Just to test it, I would again turn on key, and plug and unplug the ICS to see if you can hear it click. When mine acted up, it was oddly rare for me to ever get it to NOT click when testing it this way. I only got it to not click once when doing this test. This made me think my issues were elsewhere and caused me to waste a lot of time tracking my issues down. But maybe yours won't click and you can confirm its your issue relatively quick. Click is pretty faint so needs to be pretty quiet to hear it.

I ran with the ground side of the ICS grounded direct to the carb for a long time with no issues with idle telling me the ICS was indeed my issue. Seemed to be for me the only way test it reliably. If you do the same I think you will find the ICS is fine and its your emissions computer or a wiring issue. Again, I would only do the ground bypass long enough to either prove or rule out the ICS as your problem. The ICS is designed to prevent unburned fuel from entering the exhaust on deceleration, so you really want that working if possible. Doing this bypass basically opens the ICS anytime you turn the key on, bypassing the control the emissions computer normally provides. Just rule it out as your issue and move on to other ideas posted here. Its quick to try and should tell you much about your issue.

To run the ICS ground bypass, simply split the ICS plug, jumper the hot side across to the ICS and then run a jumper from the ground side of the ICS (on the actual solenoid side of the harness, not the truck side) to a screw on the carb body. Photo here:

Not the greatest shot but hopefully you get the idea. HTH.

IMG_3132.jpg
 
Last edited:

Robert Franzke

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Messages
1,129
Location
Plano Texas
Not to beat a dead horse here, but remembered this video illustrating how the ICS system works. I found it very helpful in understanding the point of having the ICS in place.


Thought it was good stuff so thought I would add it here. HTH.
 
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