tIIsleeper

At certain throttle positions my car seems to be cutting fuel and then adding fuel randomly. It only occurs on the first throttle plate portion of the gas pedal and my a/f guage goes from rich to full lean very rapidly back and forth. I dont feel any bucking but some slight hesitation when i give the car a little gas. It doesnt do this when im boosting. I have regrounded almost everything in the car except the injector/ecu ground under the intake manifold which I know is a problem but I plan to do that when i swap my injectors. It only does this under load...not in neutral. Any help would be great, thanks.

NZConvertible

That's the ECU shutting off the injectors when the throttle is closed (or nearly closed). The injectors are tuned back on when you open the throttle or when engine speed drops below 1500rpm so it doesn't stall. Pretty much every EFI system in existence does this. It saves fuel and prevents bucking on decel. When the injectors are off an A/F gauge will show full lean for obvious reasons.

That's probably an out-of-adjustment TPS, as this is what tells the ECU whether the throttle is closed or not.

That's because the throttle is open.