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possessed 5.3 swap.. help

Conversions & Hybrids - LS1TECH - ls1tech.com
So, I need someone to talk me off the ledge with this thing. Running out of ideas

Truck is an 85 S-10, with a bone stock 100k mile 2000 5.3/4l60e swapped in. I did the harness per LT1swap.com, and Brendan did the tune. Has some goofy quirks, and is pig rich.

First issue- I cannot shake a P0121 code. Throttle body is spotless, brand new Napa TPS, checked ground, has 4.98 volts on ref wire, has continuity on the signal wire between the ecm and sensor plug. voltage at idle is .40, but only 2.93 at WOT. sensor will go to 9.95 off the throttle body manually cycling it. The wierd thing is my scanner will show 0% throttle and 100% at wot. Im not sure what to do with it. Did the relearn multiple times.

Second issue- Toss the truck in gear it will sit and idle, as soon as you touch the throttle it will try and spike to 1500-2000 rpm and stay there. Will run through town on its own at 40 mph with zero throttle input, and showing 0% on a scan tool. If you bump it into nuetral it will spike to 3000 rpm on its own. When you come to a complete stop it will finally idle down and sit there instead of trying to push through the brakes.

I've swapped MAF's, a TPS, a MAP sensor, everything but an entire throttle body at this point, cant find a vacuum leak, fuel pressure is a touch low (45-50 psi) but would that cause a bunch of this? Suggestions, thoughts, ideas?
Date: Jan 14, 2018   


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