Need help engine wont rev

[GOODOLEBOY84]

hi i need some help with my f150, its a 84 2wd, 302 aod, when you try and rev the truck it gets to about 2000 rpm and it starts cutting in on out, and back firing, it acts like it not getting any fuel, it has a edelbrock 600 cfm part # 1406, with a factory 4 brl intake off a 84 mustang, im at a lost i dont know what else to checked? also when you disconnect the vaccum advance the problem seems worse, the timing is set at 12 degrees, it was running fine and the truck set up about 3 or 4 months never really got drove except to move it around the yard, i change the tires and wheels on it and when i drove it is when i found it was running poorly now?


here is whats been changed:

distributor
ign module
coil
fuel filter
carb was taken apart and inspected

 

[Capt Jay]

I'd run down vacuum leaks.

 

[Capt Jay]

Or did you do anything else in the fuel system. You may have a clogged fuel filter. The filters aren't that large and can clog easily. I put a new tank in my truck and it had contaminates in it. I went threw a half dozen filters until it cleared up.

 

[GOODOLEBOY84]

it idles perfect starts great, fuel filter has been changed, 99% sure there arent any vaccum leaks

 

[Capt Jay]

How long ago was it changed (fuel filter) and did you do any work since then? Is the coil good/tested? Did it run well after the work you've done or has it not run well since then?

 

[BlackBII]

If it wont rev, it must be either a timing or fuel delivery problem.

Or a rare case of air delivery, but I doubt that one.

 

[GOODOLEBOY84]

fuel filter was changed yesterday, dist was changed today, its getting plenty of fuel and the coil and module are off of a different truck but i know they are good because i drive that truck everyday, i tested the voltage at the coil and its 10.2 volts idling, the voltage at the battery is 13.9, when you rev the truck up the voltage at the coil goes to 12.3 volts, im gonna test the wires between the ign. switch and coil i know it has a 1.1 to .5 ohm resistor in the wire, i think ive narrowed it down to the ign switch but just not sure i will see when i get home, i have to ohm the wires and see

 

[GOODOLEBOY84]

How long ago was it changed (fuel filter) and did you do any work since then? Is the coil good/tested? Did it run well after the work you've done or has it not run well since then?

the truck sat for 3 to 4 months, when i got it out to start driving it again this is how it ran, so ive been trying to track the problem down since

 

[Capt Jay]

Try/switch the coil wire.

 

[martin]

What distributor is in it?

 

[V8 Level II]

the truck sat for 3 to 4 months, when i got it out to start driving it again this is how it ran, so ive been trying to track the problem down since

Old fuel?

 

[GOODOLEBOY84]

how can i swap coil wires it has a plastic clip piece that clips onto the coil? it has a reman factory duraspark distributor in it, no gas is fine

 

[kimcrwbr1]

Have you checked the float level. Is the choke open all the way when it is cutting out does it blow smoke. Kinna sounds like the power valve aint opening when the vacuum drops to its range is it low on power a few seconds after you floor it. Once the accelerator pump fuel burns off. Just throwing stuff out there.

 

[GOODOLEBOY84]

float levels are fine, doesnt have a power valve its a eldebrock 1406 600cfm,
ive determined its a electrical problem but just dont know what yet

 

[kimcrwbr1]

Have you put a timing light on it to see if it advances properly. Try advancing the timing until it pings under a load and back off until it just stops pinging. Using the damper to time it can be deceptive if the damper pully has shifted from age. The timing by engine ping is the best way to set the timing on MSD ignitions. I am guessing you have the duraspark sense you have the vacuum advance. Do you the advance disconnected and plugged when you set the base timing. Also are you using a vacuum guage or a tach to adjust the idle air needles you want the highest vacuum pressure or rpm when adjusting the needles then check that they are within 1/2 a turn between them by counting the turns in then back out when the engine is off. I would try advancing the timing first set it where it almost pings at 35 mph when you goose it lock it down then adjust the idle air.