Hey everyone sorry to introduce myself under these conditions but i've recently taken a farm mechanic position and i'm totally stumped here. I've got an 88 F250 with a 351 EFI that won't run to save my life. The tank we use (front I believe) was replaced along with pump/carrier before I started working for these guys. I did a fuel filter (poured black **** out of it), did a fuel pressure regulator, O2 sensor, and air filter. Problem is that she runs great til she gets warm. Then all hell brakes loose. 2200 RPM idle, and total stall under any throttle at all and she stinks like gas under the hood. I pulled a plug and it looks great, straight corners on the electrode and doesn't smell of fuel. I pulled the TPS and cleaned it all out and it didn't help. With the intake hoses removed the thing SCREAMS through the TPS hole. I've used the old farmer method of finding a vacuum leak (hosing the motor down with ether) and found nothing. Would a plugged cat cause this? ( I only ask cause they have a fuel barrel for the tractors that had leaded gas in it - from what they say - "we don't run that gas in our truck") We are running on limited funds so the most direct answer would be the best but I'm willing to try anything cheap and quick at this point. Also, While the truck was at a decent idle (800 - 1k RPM) I jiggled the MAP sensor and the motor changed idle a bit. I've tried pulling the EGR vacuum line to no avail. Usual idle is around 1500-2200 RPM. I have zero experience with these motors and am at a total loss here. Thanks for your help in advance.

 

You should see if there are any stored codes. Removing the TPS may have created some problems for you if you didnt first scribe a mark so that you could get it back where it was. The IAC you could pull and clean/test that, take a look here, all links are on the right
Ford Fuel Injection » Throttle Position Sensor (TPS)

 

tps is what first came to my mind. haines/chilton manuals have pretty thorough step by step voltage/resistance tests for all of the sensors on these trucks. i'd say its sensor related, and you can test all of them in under an hour once you have the book.

 

Ford Fuel Injection » How To Run a Self-Test
Ford Ranger/Bronco II EEC-IV Testing

 

Well from what I hear these problems are quite common. Threw her on a scanner and here's what I got

KOEO
31
81

Mem
34

KOER
21
41
31

I'm sure you guys know what this means.

I was "guessing" an EGR problem and while removing the system for cleaning EVERYTHING broke. Plugged it all and it didn't change a thing. Once again the problem only comes up when it's HOT (running over 15 minutes)

Codes were pulled while she was acting up.

Turns out I didn't pull the TPS is was the idle air bypass Assy. A loud whistling noise comes q

 

Whistling noise from
The IAB valve in the TB. I have a manual and it's a total piece of garbage. I'm trying not to blindly replace ever MF'n sensor on this thing. Thanks aging guys!

 

Also when the condition presents it's self the motor acts like it's running on a couple cylinders at full throttle. Only when it's fully warmed. Full on bog for a second and a half or so then it picks up and winds out. Pulled the plug on the ECT and it still ran crappy, but better. Am I looking a TPS and ECT failure?