I've got an issue. Bought my 96 f150 with the 300 i6. Fuel injected. 299k miles.

Has sat for about a year and a half before I bought it.
Need to get her up and running. Almost done just cant figure this one out.

Here's the issue:

I have replaced a lot on this truck will provide list later.
She starts almost perfectly now sounds amazing. Runs for about 5 minutes and when the computer tells the truck to lower the idle, everything goes wrong. She runs really rough, almost dying. However, when I try to give her gas to get her back up there and alive, I have no throttle response. Only when I let off the gas is when I get a backfire or two. When I put my foot on the gas and hold it i get very little gain what so ever and you hear those backfires again.
The backfires sound like there are coming from the intake, possibly because I have the top of the filter box separated from the bottom.
When I get backfires I get smoke (as to be expected) from the exhaust. However it only smokes with a backfire.

Here is what I have replaced: some are unrelated

Air filter
Rear fuel pump
Fuel filter
Spark plugs
Spark plug wires
Ignition coil
Distributor
Ecm or computer
Rear Gas tank cleaned
Fresh fuel
Coolant flush and replaced
Oil change
Oil filter


I have been told:

Possible ecm failure
Possible fault in wireharness (rat chew)
Possible timing gear jump

I have put a lot of time in this truck and I am determined to fix it.
If anyone has any suggestions or instructions please hook me up.

I'm supposed to take this truck for a ridiculous drive soon and I need to put some miles on it before hand to make sure she ain't going to kill me.

Please and thank you

 

Any codes?

 

The dash says there are no codes. At least the light hasn't came on. Tomorrow i will check it anyway.

Also been told that the obi2 plug is ran off of the cigarette lighter in this model (I havent looked into this)
They say if the fuse is blown for that cigarette lighter then the code light wont come on.

This seems odd to me.

We have discovered a possible vaccum leak in the time since original post, and caused a few more.
Also tomorrow I will replace all the vaccum lines.

I have a video of the rough idle now. Will post shortly if I can.