db caissie
June 25th, 2013, 01:30 PM
Hi everybody, I'm new to the tuning bit. I've used my v2 for deleting antitheft, cat delete, and whatnot involved in engine swaps for older vehicles with a gen 3 a few times now, more than paid for what I've needed it for. I'm having an issue with one of my fathers p/u's. It's a 98 l31 5.7 with the black box. I've rebuilt the 5.7 vortec with a balanced bottom end, mildly ported heads, small cam upgrade(unsure the exact specs, so called "rv cam"). New everything on it including the 4l60e behind it. We're having an random missfire. I've been over and over and over this thing trying to find something, bad wires, fuel delivery, something, can't find anything. All the work I had done was prior to receiving my v2, and we had an out of town dyno shop do a tune, due to deleting the cats and different tire sizing. To get to the point, I've done some data logging and found that when the miss happens the rpm jumps wildly up to 7500for one frame, then back to where ever it was at, the injector flow rate jumps to 80%, the spark retards way back, but not much else changes, vss stays consistent, map, o2's, tps, all stay what looks normal. Hopefully somebody can help a bit with this. I'm banging my head against the wall, I know there is more in this engine for tuning, but I need to solve this problem before moving on!