Hello, I've got a 1989 F-150 with the 5.8 and a C6. The problem I'm having is when I start the truck it will start then either die or hunt for a couple of seconds then die. the only way to start the truck is to rev it up to about 1500 rpm and hold it for a couple of seconds. once i let off it idles fine. sometimes after starting it will run rough (almost stall) and then all the sudden just run perfectly, like someone slapped it and woke it up. it doesn't matter if the truck is already warm or cold it still does this. although it does tend to start better when it's cold out (around 35-45 degrees). the truck also runs rich.
I haven't done a lot because I'm a poor high school student, but I have replaced the plug wires, IAC, fuel pump, fuel tank, water pump and thermostat. (not all done to try and fix this problem).
the PO also removed the EGR system. I don't know if a problem could be because it's a different engine. (came with a 5.0 and an AOD) and the PO didn't do something right?
Any ideas?

 

Check for codes first.

 

It sounds like your IAC isn't being controlled properly.

But I second, check for codes first, it's free.

 

The ACT and the ECT are the sensors that mainly control idle speed according to how hot the engine is
Test the sensors and verify the voltage from them
Sometimes neither one of those sensors will set a code
Test the codes anyway

 

Ok I checked the codes.
I got 81, 82, 84, 13, 12, 54, 87, 16, and 33. I believe that code 33 refers to the EGR system, and because my truck doesn't have that I'm not worried about that.
according to my Hanes Manuel, code 12 and 13 both refer to the RMP not within the self-test upper/lower limit. which would make sense. code 16 is RPM too low to preform oxygen sensor/ fuel test. 54 is intake air temperature sensor circuit open. 81 and 82 are both speed control vent circuit failure. 84 refers to the EGR system so again not worried about it. and 87 which is primary fuel pump failure.
some of these codes were KOEO and others were KOER. I think I should tackle code 54 first because it would explain why it sometimes starts better in the morning. thoughts?

 

Fix KOEO codes first, they're a good place to start

 

Just an update, I've taken the intake off to inspect and clean. it was caked with black sludge. I also replaced the throttle position sensor (it was showing bad values). no real improvement. so, I've ordered a new AIT along with some other necessary parts on rock auto. they should arrive at the end of the week.

 

Re reading your Op I think I would take a look at the processor
Your caps may be leaking and those older ones get to missing badly when that happens
Then all of the sudden they will run fine for a while then do it again
Also, I would wiggle test the harness that runs around the rear of the upper intake
They have a habit of chaffing in that area and shorting out the injector harness
Have fun
Your new IAT and or ECT might solve the initial lack of fast idle and stalling problem

 

Ok, I forgot to mention that I found the old ECT sensor laying in the engine compartment when I took of the intake. So, the PO must have been chasing this problem as well. I'll check the wiring harness by the intake today when I get home from school lol. also, I believe the PO messed with the idle screw. after reading a lot of posts most people say to never touch them. could that be a problem? is there a way to "reset" that screw? Thanks.

 

Yes, there is s set procedure
It used to be to disconnect the IAC (air bypass valve) and set the screw to idle (or just about die) at 550 RPM
If it were mine and somebody mucked with the screw, I'd just go get another one (unmolested one) from the junk yard
After you get some of the basics figured out
Work on that code 33, if the processor sees no EGR pintle valve movement from the EVP sensor it throws the truck into a sort of limp mode

 

Wait so it could be because the PO removed the EGR system? also I removed the ECM and took it apart. I didn't see anything that was a red flag. I only saw one blue cap and it looked fine. upon closer inspection it looks like this is a remanufactured computer and it has a code scratched into the plastic. upon reinstalling the computer and turning it on it now runs worse at idle. like it won't even idle right unless you go drive it. what other diagnostics can I do to the computer? also can I just go to a junkyard and pick up a "new" computer?

 

There are good used ones at the junkyard at times
You really need to match up the numbers and calobration tag
We used to just grab one and at the junkyard see if it would then pass emissions. Then worry later about getting the correct one for clutch v/s automatic, 4x4 etc.

 

Ok, I've replaced the ACT as well as clean the whole intake system. it's not perfect but its def better. it seems to start a little bit better but still not how it is supposed to. when I started it this morning, it stalled like it does but upon restarting it was coughing and choking until I hit the gas pedal a few times. when it did fire it was missing pretty bad until a few secs later then it was back to norm. seems to me like it was getting flooded with fuel. could a have a stuck injector, or no?

 

Ok, I messed the PO about what he had done prior to me owning it and he said he did not replace the IAC. However it looks practically brand new. I opened it up and it looks like it just came off the shelf. However when I tried to reset that idle screw, the IAC literally did nothing. Like the engine is only running on the idle screw. Is there a way to check the function of the IAC? Ohm values and voltage? Also I took the computer out of the truck and took it apart. And was honestly a little intimidated on what I was looking at. I couldn’t find any videos that matched what my computer looked like inside. Somebody also like scratched a code into the side of the plastic. Kind of scummy. Anyway the side of the computer also said remanufactured. So I just cleaned it out with some electronic cleaner and put it back in. No change.

 

If unplugging the IAC has zero effect on idle, it is either not receiving power from the PCM, or it simply isn't functioning