2F idles but falls on face above 1000K (1 Viewer)

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1984 FJ60
If anyone can help I sure would appreciate it. I think I have the truck sold if I can get it running right. Here are the particulars:

Truck starts with some patience and idles initially at 6K. Up to 800 when warm.
If I go to give it the gas, it falls on its face and dies before 1000.
Rebuilt carb - Holley - no change in behavior.
Replaced fuel filter - no change
Desmogged and very simple.
Fresh engine
DUI dizzy
Recently replaced fuel pump with a used one (supposedly good). Before that it wouldn't start at all. After fuel pump it ran great for a while.
Seems to have good fuel. Acc. pump works good.

Any Ideas? Thanks.
 
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i'd definitely say you are doing great if it happens just shy of 1,000,000 RPM's!

hehehe - couldn't help it...

I'm in the same boat. selling my 87 now that new 85 is coming home soon w/ 5sp... but need exhaust gasket on my 87 to get it running better/quieter before selling. Just one of those things...

GL!

rob
 

FJ40Jim

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Remove level plug from side of bowl.
start engine.
Rev engine.
Did fuel level stay up near plug, or did it fall way off?

If fuel level stayed up, then problem is in main circuit of carb.

If fuel level dropped way down, then problem is in supply (tank,filter,pump, needle&seat).

Oh, reinstall plug before you start a fire.
 
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Jim: I would like to try your procedure however, I am unable to rev the engine at all. At idle, there seems to be enough fuel in the bowl. After it dies, I can advance the throttle at the carb and both jets will fire fuel into the carb like they should. Is it possible the fuel pump is working just enough to let it idle but not enough to rev the engine?
 

FJ40Jim

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The jets are not firing fuel after the engine dies. That task is handled by the accelerator pump.

So you know the AP is working.

But it sounds like a main jet is restricted.

Try this experiment:
Start engine.
Try to rev engine by "jacking" the gas pedal, applying throttle is little pulses to repeatedly work the AP and make it keep squirting out gasoline.

If the engine tries to run whenever the gas pedal is being pumped, but won't run when gas pedal is held steady, then it is running on the AP fuel, but is not getting sufficient main circuit fuel.

OTOH, if it just won't run, even w/ pumping the AP repeatedly, then there is another problem.
 
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Thanks Jim for all your help. I know you are very busy. I tried feathering the throttle and it just won't accelerate at all. Starts right up after it stalls though if that helps. I may be interested in one of your rebuilds. How are your current time-frames looking? Any other ideas? Could it be the fuel pump or something electrical? Thanks again.
 

FJ40Jim

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It is not likely to be a mechanical problem.

It could be ignition. Ignition load is lowest at idle, highest when accelerating or under heavy load.

Could be a lack of fuel above idle.

Could be a lack of airflow. (restricted exhaust or air intake)
 
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Update:
I think I have found the problem...at least one of them. I have a header and therefore one of those MAF plates on the bottom of the Intake for circulation of coolant to warm the carb. With the carb off, I noticed some antifreeze inside the intake. Took it off and found a crack that must be leaking vacuum and antifreeze into the intake. Will get that fixed and see what happens. I am also going back to original carb, etc. from a Holley setup. Does the cracked intake explain why it would idle and then just drop off after 1K? Appreciate your thoughts.
 
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Mine was the catalytiv converter was completely clogged. Would idle fine then fall on its face. Took the cat off and started and it ran fine after.
 
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Update:
Well since my last post, I have done the following:
- Replaced the intake/exhaust gaskets - no leaks there now
- Replaced the Intake manifold
- Replaced the Holley with a stock carb
- Ran a new fuel line to the carb
- eliminated all possible vacuum leaks
- New fuel filter

and I still have the same problem. The truck idles great now...very smooth at 700 RPM. Go to give it some gas (fast or slow...doesn't matter) and it just falls off the cliff like a rock at exactly 1000 RPM. Real sudden drop off. I have had three different carb set-ups on it and no change in the problem so I have to assume it is not the carb or a vacuum leak. The fuel is right up where it should be in the carb window at idle so I assume the fuel delivery is OK. I am thinking it must be ignition related but here is the rub. It has a new MAF DUI distributor with the expensive wires. How do you check the coil on these things? Another thought was that maybe the fuel cannister has something to do with this....some kind of clog or something. Does any of this make sense. I have been dealing with this for months so any direction is most appreciated.
 

Trollhole

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Take cap off gas tank and blow compressed air into the fuel line. Possible you have a blockage in the tank. That or run a hose from the pump to a gas can.
 

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