I've heard of an issue with other makes and model where the fuel tank doesn't vent properly causing a vacuum situation because of the gas cap not venting properly.

They recommend driving with the cap off to see if some of the symptoms go away. or right before it starts to act up, remove the cap and listen for air being sucked in.
Never had to try this myself.

I would grab the codes first like others keep saying.

 

could a plugged intake be causing this..ever hear of this?

 

I've heard of the fuel pickup screen getting clogged causing the symptoms you describe, also the fuel filter, the pump itself.

That's where I would start. I also read you have "lots" of fuel pressure ?
You should really test that to make sure as others have mentioned.

I myself live on a tight budget, so I try to shoot for the obvious cheap fixes first, then the cheap but hard to get to. If absolutely neccesary, I'll drop a dime or two

Have you replaced the fuel filter?
This would be budget item #1 on my list

Oh, listen to the kernel............ much knowledge and very helpful !
........... Wax on, Wax off

 

well fellas heres what i did today, i went to the auto wrecker got another eec-iv, tfi, and tps...i replaced the tfi 1st started it and did the same thing, replaced the eec did the same thing, replaced tps did the same thing...

heres a list of what ive changed.

Low Volume Fuel Pump (in the tank)
High Volume Fuel Pump (on the rail) (i can hear both pumps working 100%)

filter screen in the tank, big black canister filter (had no filter so i put one in)
bigger filter by the engine
Throttle Position Sensor
Thick Film Ignition
Fuel Pressure Relay
EEC-IV
and numerous relays

im stumped guys, like this is pretty much my give up point unless anything else happens


can the o2 sensor on the exhaust cause this? if i swapped computers will it make it run rough for a while?? could the throttle body be clogged?

 

Have you tested / cleaned / checked your Idle Air Control valve? I wouldn't rely on junkyard parts, especially for TFI modules and computers. You may or may not get something that is 100% in working order. Sometimes it takes brand new parts to fix things. Did you re-check your FPR as well? I don't see how it would fail so soon, unless the one you put on was used and was on it's way to failure anyhow. You may also want to clean everything you can, as far as the throttle body / upper intake / EGR / IAC. Kinda sucks you get the damn thing running good and then it goes back to not working for *****

 

havent touched the idle air valve (ill have to look up on it) you got to figure with junkyard cars tho, they didnt go there because the eec or tfi has broke down, its something way more major, thats the way i look at it...the FPR i got from a guy was only used for 3 months then he got rid of his bronco and kept some key parts. can the throttle body, or intake get clogged to make it not work? how about the o2 sensor??

 

O2 sensor would just make it run rich or "stumble", not completely die. Two of the key pieces that would cause your symptoms other than faulty fuel delivery components (pumps, filter, relay, inertia switch, FPR, etc.) are a bad TFI module or the IAC. You may also have a pickup in the distributor that may not be working well, either. Anyone else have any thoughts?

 

tomorrow im going to take that screen off the primer filter inside my tank and run it w/o that, i hear that can be a possibiltity...how could i test this air control valve?? i know earlier today i took it off to give a look at it, but im not sure what to look for....whats this about a pick up coil on the dist??? i took a dist. out of a 3.0L ford today and parts were looked up so it matches my dist. in the bronco right now..what are symptoms of a bad pick up coil?

 

I agree with the pickup coil also, has the same symptoms you described.
Stalling when warm would happen.

Age, moisture,cracks, letting it expand and contract. That could create an open circuit.

Worth a look.

You can unplug the IAC and the rpms should drop way down, that usually means it's doing it's job
It will also set a code for being out of range.
My bronco would actually choke and die. Once I cleaned the throttle body
it quit dying, just idles real low.

If you remove the elec unit from the valve there will be a small rod sticking out that should open and close the plunger that regulates the air. when the unit is attached it should open the plunger about a 1/16", carbon builds up
and can restrict the air flow.

I just took it apart and cleaned it real good with intake cleaner.

 

Why are you pulling the tank when you already put in a new intake filter and fuel pump? Have you ran codes yet? One thing that can give you these symptoms that has not been discussed is the negative cable from the battery to the engine. If it goes bad it can cause your truck to run rough and not start. This caused mine to start when cold but not when warm.

 

Good point, newbii. I also thought of something else. Are you sure you primed it up properly? I think the magic number is like 7-8 times turning the key to run to let the system re-prime itself, or, you can also use the jumper wire to the test connector to run the pump manually. I have to agree, though, "lots of pressure" may not be 30-40 psi as required for the system to run, not to mention, if you didn't re-prime it fully, you'll have an air pocket in the line that may cause this. The pickup screen could be clogged, so can the fuel filter, which would also cause problems. You may also have junk in the tank. But... going back to the original problem, wondering if any of the battery cabling or grounds are screwy as well. Lots of things to consider and check / re-check.

 

well heres what ive done today, came home from work, dropped the tank, checked for leaks, kinks and what not, took out the fuel pump and inspected everything and it looked good, bench tested it and i heard it, this is the 1st time ive ever tested the pump inside the tank, i took the pump, placed it back in the tank like it should be, sealed it etc... and then i tested it in the gas tank, no gas or nothing came out, i hustled down to the local parts shop, and got a brand new fuel pump...came home put it together, put it in the tank, and tried the test again (if no gas came out then i know its a diff prob) so i tested it and gas shot right out so JACKPOT i thought...the small pump wasnt priming or bringing gas up, EURIKA IM SO HAPPY...put it in the tank, put the tank up botled it up, connected the lines, fired it up.....still the same old bull ****...i might just have to push it onto the road and hope it gets hit.....my theory on the neg cable on the batt, if it wasnt grounded properly then LOTS of other things would be screwing up aswell.....also i figure if it had to be an elec. problem then it would effect my vehicules starting etc.. as soon as it dies i can fire it right after every single time, it fires up so quickly....im just lost

 

Don't give up, I almost gave up on the beast.
threatened to drive it off a bridge and everything.

Is it slowly just dropping rpms and stalling or just flat out dying like
someone just turned the key off?

 

slowly stalls, it idles good then it drops 2-400 in rpms and then i push on the peddle to keep it going but nothing, but when i release the peddle its like it got gas and wants to go running...i could press on the peddle tons when its starting to die and it barely helps keep it alive until i let go of the peddle

 

well i just finished checking over a ton of wires, checked tons of grounds to see if they're loose and what not, nothing at all, even checked the neg wire solid as a brick, think i could just straight wire the pumps to the batt and have switches in the cab?