Ok, its time to pull this thread up from the dead.
I replace ignition components I was having problems with. Eventhing ignition wise is solid....no more misfires with flex fuel disabled. However, it misfires like crazy under high load with the flex fuel (FF) enabled.
I have the FF port set to PEO/JS7. It works fine at low rpms and low loads, but starts to misfire over, umm, say 3K and 133kpa. The signal just gets noisy.
I have the 12v power feed running off of a fuse block that powers the MS, the injector (with the flyback hooked to the injector 12 line), fans, a/c relays, gauges, nitrous, and the stock 30amp ignition circuit that was originally there (use the stock 30 amp ignition wire to just turn on a 100amp continus relay to power everthing esle) so I can imagine there is some noise here, but cannot determine without a scope. ( the DMM reads stead voltage, but may not refresh fast enough to pick-up fluctuations). The main power going to the relay is attach to a 0.5 farod audio capacitor to heldp reduce noise too.
The low refrence ground for the FF sensor is wire to the same ground point on the engine that he MS is wired to.
The ground on the engine goes to a ground point on the frame, then a seperate ground on the frame hooks up to the capacitor with some other stuff on the grounded to the cap as (nitroud, fans, a/c control relays).
What would be the best way to eleminate noise on the FF sensor line?
Should a install a small capacitor (22pF) between the ground and 12v on FF? Move the 12v off the fuse block?....move the ground to the battery or capacitor? I'm tempted to reroute the ground to the cap, but with the fan grounds already there, I can imagine is noisier then the engine.