Stumbling and misfire under load on 2001 LIghtning

S

sho14u

New member
I own a 2001 LIghtning and have had it for 10+ years. I love the truck, as we all know. The mods that I have on it are an underdive pulley, intake, exhaust and a matching tune. The truck has run on this setup for about 8 years and it has been awesome. Over the past year it has started to miss here and there under boost?load. A few months ago I popped a plug and had to have the dealer put a helicoil in it and that was fixed... But the misfire issue progressively got worse. I replaced the fuel filter, COP's, and plugs. Still runs like crap. I checked for disconnected vacume lines, and cannot find anything. It does not pull any codes, and I cannot even get it to show a misfire on the reader. I am at a loss... I am an avid mechanic and I am not sure which direction to go now. Is it possible that I have a bad fuel pump? I don't know how to test this to see if there is an issue. Any help and advice would be greatly appreciated. I don't want to take it to the stealership and throw a bunch of money at it if I can fix it myself.
 
Just a few things to throw out there. I have been researching online for similar issues and have a few options to look at.
1. Plug gap. Everyone is saying that they should be 32, I will check the gap on my plugs tonight when I get home
2. Fuel pressure relay?
3. Fuel pump relay
4. Throttle Position Sensor? (if it was this, wouldn't it throw a code?)
 
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