97 460 issues....

[rusty ol ranger]

97 F250 HD.
460 EFI/Auto*
86000 miles.

Yesterday going to town i noticed something...off. Taking off from a redlight the motor felt like it kinda bogged and missed, but seemed to come back right away. I didnt think much of it.

Now today, its bogging and missing, but only under load. In park it revs beautifully.*

If your driving you can feel it miss, bog, and just generally feels like it has no power, well, less power.

If you brake torque it, locked in 2nd with the A/C on you can feel it go to missing at about half throttle.

Also, i noticed it running rough immediatly after a hot start, but only for a minute or so. Like, almost stalls the truck rough.

I havent done much diagnosing yet, but i have no check engine, no smoke, and it only does it once you get it warm.

I pulled the dist cap and cleaned the corrosion, it made no difference. Top end was gone thru at 68k and bottom end at 84k, so i doubt its valvetrain.

Im leaning toward the ignition module...or maybe a plugged cat? Im not real sure, this is my first forray into dicking with this kind of issue on EFI.

Thanks in advance

 

[alwaysFlOoReD]

Checked plugs and wires?

 

[rusty ol ranger]

Plugs only have about 10000 miles on them, i guess i could start with wires and dizzy cap/rotor, but, its not acting up till the motor gets good and warm

 

[fastpakr]

Got a fuel pressure tester? Would love to know what that looks like when it's acting up.

 

[rusty ol ranger]

I dont have one no, but i may pick one up so i can see.

After doing some reading i guess it could be the fuel pump, but it does it on both tanks, so maybe filter? I dont know, ill pick up a tester this weekend and see what i come up with.

 

[BlackBII]

This definitely sounds more like a fuel delivery issue than a spark issue. I

I would check fuel pressure, test the throttle positioning sensor and also clean the mass airflow sensor.

Have you checked for vacuum leaks?

 

[Ozwynn]

My 1990 302 is doing that.... check the cat yet?

 

[rusty ol ranger]

This definitely sounds more like a fuel delivery issue than a spark issue. I

I would check fuel pressure, test the throttle positioning sensor and also clean the mass airflow sensor.

Have you checked for vacuum leaks?

I havent checked the TPS, and mine is a MAP system.

BDAB, no, i havent checked the cat, but it doesnt seem to be getting hot or stinking....

What leads me to blame ignition is the thing runs fine untill its ran a good, 30 min or so. Correct me if im wrong, but wouldnt a fueling issue manifest more when cold/initial start then after its been running?

But i also dont have any check engine....

One guy told me to replace the coolant temp sensor?

Keep the suggestions coming guys...

 

[fastpakr]

Just to clarify - the check engine light does come on when you first start the truck, right?

 

[rusty ol ranger]

Yup. Its not burned out. Lol.

Its still EEC IV, i know they dont always catch everything...

BTW, whats the pressure spec for fuel? Cant get a straight answer on google. Guessin 40 ish?

 

[lil_Blue_Ford]

I think for fuel pressure it's kinda like the Rangers, it depends on if it's a returnless system or not. Want to say the pressure specs I had found were similar to Ranger pressures.

When you check the pressure, check it at idle and under throttle. It may be fine at idle but falling off under demand.


Sent from my kite using a trebuchet

 

[fastpakr]

97 should be EEC-V / OBD2.

 

[rusty ol ranger]

97 should be EEC-V / OBD2.

Thats what i thought to, but the plug is under the hood...my 96 150 with a 300 was OBD 2 and had a port under the glovebox kinda.

Lil blue, thanks, if it only does it when warm though, and on both tanks...what could it be? Or do these run the 3rd pump on the frame rail like the older ones?

Ill hopefully know more this afternoon.

 

[fastpakr]

Interesting. Maybe the heavier trucks waited a couple of years longer.

 

[rusty ol ranger]

Well, im doubting its fixed for good but...

I started off by just changing the fuel filter, thought id get lucky....

The old one was so plugged it took all i had to blow thru it. So far, so good. So we will see. I still find it odd it only did it when warm....

But im guessing that a 460 under any load needs every drop of fuel it can get thru a 3/8 line, im gonna hope and pray, i really need this thing to stay on the road longer then 2 or 3 weeks at a time so i can do some much needed maintence on the old 77 before winter...