rallye26

Im about ready to scrap this thing its so frustrating! The truck is an 88 F150 with the 5.0 EFI. My problem is the truck starts and then dies right away. If I give it gas, it will stay running but has a lot of hesitation...if I let off, it dies. If I hold the gas a while until it warms up, then it will stay running, but seems to miss a little bit. Once warmed up, it has hesitation going down the road and seems to have a slight miss unless your on the gas hard. If you stay on the gas hard, it seems to get up and go great like nothing is wrong. So far I've replaced plugs, wires, cap, rotor, air filter. The EGR valve was stuck so I pulled it off, cleaned it up and got it freed back up then reinstalled. Pulled the Idle air control off and cleaned it up and reinstalled. Still no changes. I also checked fuel pressure at the rail and it reads great. Sprayed carb cleaner all over the vaccuum hoses trying to find a leak and found nothing. So now Im just stumped.
So far the only things I've found it may be are the PCV, and an Air induction valve on the throttle body. Is this induction valve just another name for the idle air control, or is it something completely different.

Anything else anybody suggest that I replace, or take a look at?
Thanks in advance guys...looking forward to getting this guy back in top shape.

qdeezie

I'd look at the fuel system. Have you ever replaced the fuel filter or the pressure regulator? I'd start with the filter at the minimum.

1989-FORD-F150

X2 check the fuel injector or Seafoam it to clean out the fuel injectors they might be clogged up bad or something

rallye26

I haven't changed the fuel filter or FPR yet. I checked fuel pressure at that port on the manifold and it reads good no matter what RPMs im at...so thats why I was leaning towards something else. Still think I should try replacing both?

wde3477

Suggest to check the Idle Air Control (IAC) solenoid. Our vintage was prone to carbon build-up causing the piston to stick. A little bigger than a roll of quarters, straddling the main throttle butterfly. Haven't heard the term 'air induction valve' but it sounds like the same critter.

Two phillips head screws and an electrical connector to get it off, then clean with carb cleaner and work to ensure free movement. Try to avoid letting carb cleaner get down in the electric coil part.

As far as the rough running, suggest to check the tubing to the MAP sensor. This is located on the firewall up near the hood weatherstripping, slightly to the passenger side. A crack or hole will give false manifold pressure feedback to the computer, which screws up the air:fuel ratio. Suppose it's possible the MAP has failed, but I can't recall of hearing about any failures.

Good luck, and keep us posted.

rallye26

I did pull the IAC off and cleaned it all up. It wasn't too bad already but I it did free up a little bit from what it was. Hooked it all back up and nothing changed. Still not sure what the Air Induction valve thing is I read about but its almost got to be the IAC...there isn't anything else up by the throttle body that I can see.

I'll take a look at the PCV vavle and MAP sensor tubing and see if that helps at all. I'll report back if anything changes.

Thanks for the help!

BigGreyBox

Sounds like the IAC could still be bad. Cleaning it doesn't always fix it. I cleaned mine and it still wouldn't work right. So I replaced mine with a new one. You can test to see if it works at all by getting the truck to idle then unplugging the IAC. If the truck doesn't stall or start idling way worse, then its faulty. Could also be the timing. Check to make sure the timing is set right, and make sure all your plugs and plug wires you changed are tight and installed right.

Ace_Savant

I'm having the exact same problem on my 1989 Ford Bronco (302, 5.0L). It starts after you crank it, then just sputters and dies. Did you have any luck with a solution? This problem is really frustrating.

Just as described above, I tried driving it around by way of holding the gas pedal to keep it alive, and it hesitates all over the low RPM range, but once it gets to about 1100RPM, it accelerates like its running great.

What I've tried:

Checked FPR, no fuel from the nipple and I get 38PSI on the rail continuous slightly increases when I rev.
Replaced the ECT sensor.
Replaced the IAC valve.
Replaced the ERG valve and sensor.
Replaced the TPS.
Its difficult to check for vacuum leaks accurately when the engine won't idle for more than a few seconds at a time.


Interesting note:
When I unplug the IAC valve, the truck idles at around 500 RPM for about a minute and then sputters and dies like it normally does.

Anyone?

first

Check out my post. I was fighting idle quality since I bought the truck. Chaged and tested everything fuel, air and spark over and over till I came across a Ford TSB on idle quality/stalling.

https://www.f150forum.com/f10/errati...ly-gear-68171/

A $50 dollar part from your Ford dealer and it ever comes with new gaskets. I recommed keeping the plug in that the instructions say to remove if you have a 5.8 or 7.4.

It will take some time to get the idle set if you do it by your self. My truck will still idle rough like the IAC can't keep up or glitchs but I havn't had it stall out since I've put it on.

Ace_Savant

Well its been a while and I'm still having the same problem. I tried the idle air plate from the previous post, no luck. Replaced my O2 sensor then it acted like it was going to run fine, but started doing the same thing a few days later. Really frustrating and I am about ready to give up on this truck. Anyone else out there run into this problem?

Truck starts then stumbles and dies. When you get it warm, it will run, but won't idle quite right. Lots of hesitation at anything below 2000 RPM. Once it gets past 2000, it runs like everything is great. I've checked for vacuum leaks, tested each and every line personally. Replaced HEGO, Replaced IAC, Replaced ECT, Replaced ACT, Replaced EGR and sensor, Tested fuel pressure (36 at idle, goes between that and 40 elsewise.), checked FPR (No fuel from it or any other indication that its bad.), new Spark plugs, distributor, rotor, cap, ingition wires, ignition coil, Hell the entire engine is a rebuild from a local shop, no suspected problems.

Keep in mind that most of that was not replaced while trying to hunt down this particular problem, but out of necessity when I replaced the engine. However, all the replaced hardware has been tested in every way I've found how (resistances, voltages, ect.) and conforms to known specifications.

Has anyone else out there run into this?