Ok guys i have a huge update. All codes are gone, i replaced all vacuum lines and ECT after i found out it was corroded, and i rerouted the egr vacuum solenoid straight to the manifold, and sealed that exhaust leak up furthur, my mileage has improved a little bit. HOWEVER, it still idles high and the idle is not rough, its more like the gas is being mashed a little little bit. When started cold it shoots to 2k then goes to 1500 for a couple minutes then drops to 1000 then will shoot up a little to 1300 then settle to 1000 where it will stay, when put in drive it drops to 850 then to 1000 again and ill drive it for a few, then when i stop it will go to 1000 then slowly drop to 900 where it will stay. If the truck is put back in park, it will go to 1300 and stay, if ac is turned on then it will surge a little ( im guessing from the compressor switching on and off). Ive had the ecu inspected by several good buddies i know who know what their doing and all say it looks ok. So i. Wondering mybe its i tps or iac issue or something? I checked the TB, there are no gaps in the butterfly valves and the throttle stop screw has not been touched. All gaskets that had to do with the intake were replaced this includes, TB egr, iac, and upper intake gaskets, and vacuum lines were replaced and tightened. I have checked numerous times for vac leaks with smoke, and spray, none show up

 

Now that you have solved most other issues, now what happens when you unplug the IAC while running? My guess would be that the IAC is at fault. I had shifting issues with my Bronco (E4OD) that was due to a bad TPS. I fought that for a long time until the sensor was finally bad enough for the computer to set a code. At this point I still wouldn’t throw parts at it and hope for the best.

 

To be clear - the primary reason we suggested you inspect the PCM is because leaking capacitors are a common problem with them and one that’s easy enough to fix if the rest of the circuit board is in tact. However, just because there’s no leaking capacitors does not mean the PCM is good - it could still be malfunctioning.

Diagnosing any PCM is a relatively simple but involved process. The rule is “Check the inputs and the outputs” and for the most part can be done with a digital multimeter if you know what you’re looking for. You’ll need a pinout diagram of the PCM connector and something to backprobe it (sewing needles work very well). You first need to verify all the power and ground inputs to the PCM are good, then verify the signals being sent and received by it.

Given that the idle is changing (and no leaking caps were found) I don’t think the PCM is the problem but testing it is the only way to be sure.

Test and inspect the IAC valve and TPS sensor as I outlined for you in post #70. If those components are ok, check the wiring to the PCM for continuity. If that’s good, test the PCM.

 

Another thing i i forgot to add, is i did change the exhaust, i put true duals and drilled a new o2 sensor bung in the right exhaust pipe, could this also effect it in any way?

 

I can't remember if its been mentioned but has the physical idle adjustment been messed with/checked/reset?

 

No the screw has not been messed with.