'89 F150 Lariat , 5.0L , 5 Spd OD , 2WD , EFI

Update to my previous dilemma .
After installing analog Oil Pressure Gauge I found when motor was at operating Temp Oil Pressure was only 2 PSI , had motor removed and rebuilt by reputable local shop ( they were very busy , this took 8 weeks ) , they rebuilt the original motor and re-installed it.
Fresh Motor with new water pump , plugs , Wires , Cap & Rotor , TPS , Fuel Pressure Regulator , High Pressure Fuel Pump (Bosch)(on frame rail) have all been replaced , IAC good , Coil replaced 2 yrs ago as well as both tanks had new sending assy's put in them (sending assy's and ign. coil were replaced before I purchased but I have verified they were done) , Fuel Pressure idle pressure is 35-36 psi , remove vacuum and it will rise to about 42-44 and tank canister/switch is working and does not have the filter in it .

The motor will run and idle fine but when you go over 2000 rpm slightly loading motor it appears to be stumbling a bit , if you increase the load like going up a fairly good hill , then motor will really stumble and lose speed rapidly and will backfire through intake , the backfire is not violent but still present , had it one time on restart barely able to run spitting back thru intake in Pep Boys parking lot , then all of a sudden cleared up ...................
The only thing not replaced on this engine is the Injectors , Distributor Ignition Module and ECM .
If you run on flat ground and go thru the gears whether mild or rapid it does fine , it just has the stumble right after 2K rpm to about 2.5K rpm every other area seems fine and partial and full throttle acceleration seem fine , it only seems to be a issue when going up a hill or under load at lower rpms 1500 - 2200 rpm mostly .
This is my first Ford pickup so I am in the dark , thought maybe it was injector issue but now I feel it seems to be more Ignition Timing Related and think maybe ECM or Distributor Module could be Faulty , just have no way to nail it down , ECM is not loading any codes for any problems so this further confuses me .
One other symptom it does have that is odd is when you start it , it will idle up as normal , reach peak cold start rpm ( roughly 1800-2000) and then stall and cut off , upon restarting it will idle up and run just fine , frame rail fuel pressure is holding , pump and filter are new as well as regulator .
Any suggestions would be appreciated , I lean toward ECM or DISTRIBUTOR Module but then I have no previous experience with Fords or their controls so need help badly , Fresh Rebuilt Motor that has serious issues pulling a hill with a V-8 makes me very sad.

 

No codes at all? Not even 11?

 

I get a DTC 33 - EGR not closing Properly ( Trucks Only ) , thats a new one and would cause a lean condition
DTC 96 - Fuel Pump Secondary Circuit Fault , High Speed Fuel Pump Relay Open - This does not apply to this truck I am pretty sure , I have done on road Fuel Pressure Check and all is Good
DTC 47 - Vane Air Flow at Idle Switch Closed ( Cars Only )

Using a New Innova 1203 B Scan Tool , well I bought it when I got the truck so I could read the OBD 2

And no Code 11 due the the Codes that do not apply and the one that does , the EGR is a new one , I only got the other 2 earlier .

 

This truck isn't OBDII and An OBDII scanner won't work for it. I'm not familiar with the scan tool you are using. I would use the paperclip method and see what codes you get.

 

This scanner does OBD1 & 2 , I am going to get the EGR now and install it , not closing would cause a lean condition but not sure it would do all this , so will install and check it out with a road test , I will be very surprised if that is all of the problem but who knows .
I did the KOEO Test on it and those were the codes generated , of course the only one that applies to my Truck is the EGR not closing .

This is a very nice Scan Tool , it will work on Toyotas , Chryslers , Older GM , Ford , OBD 1 and 2 , comes with all the adapters and is computer up-datable via USB , I can print from it and all kinds of nifty tricks

Sorry I should have said OBD 1 in that post .
My Old one just did the OBD 2

 

96 does apply, some have said changing the fuel pump relay fixed it. My truck backfires like you describe when I lose fuel pressure, even momentarily. You should check the volume at the DFR for both tanks and check for proper DFR switching. That is if you have two tanks, which would mean you have three fuel pumps.

 

I have already put a new fuel pump relay in it , on this truck all the switch does is toggle power to the pumps and then the Canister/Valve takes care of the rest , I just got back from the test drive of about 60 miles , it is pulling hills just beautifully in O/D taching about 1700 rpm , also tried some hilly areas at 45 taching about 1500 in 4th , all seems well now , now I am running a powerful cocktail in the gas for the injectors as well and they could be cleaning up improving the situation also in tandem , but when I pulled out the difference was dramatic regarding power and response , one other thing I did as well just to be sure was erase the codes on the computer and then did another warm up KOEO test and the test came back clean this time , the idle when starting is still searching more than I would like so I may put another IAC on it , as that is the only engine mounted control left that is original .
I will test drive some more tomorrow but for a fresh tight motor with less than 300 miles on it , it is doing much better now , I had no clue a EGR Valve could make such a mess , I am getting a crash course on the Ford's LOL , I also just had the EGR go on my Jimmy last month , engine light came on , scanned and it said it failed , but it did not affect the motor performance what-so-ever besides bringing the light on .
With the industrial gas cocktail I am running to clean injectors , I am sure that when I go back to straight gas I will see a bit more of a change in performance as well , but the idle is smooth as silk and all the stumbling is gone , I would have never guessed all that could be the EGR