Ok so I have been going over my car (96 Cobra) for 2 weeks now trying to find what is causing a misfire or stumble when put under load. Originally I thought it was ignition related and found the #8 plug wire arcing so I replaced all the wires and plugs gapped to stock. I check the fuel system and all injectors are firing, replaced the fuel filter, and I checked for vacuum leaks and there are none. I thought the cat(s) were clogged because the engine sounded like it couldn't breathe and I was partially right. I removed the stock mid pipe and cats and put on a Bassani O/R X-pipe and the car is about 75% better. So I was looking over my SCT X4 tuner today and noticed everything was within range sensor wise except the fuel pump duty cycle was at 100% at idle and when I introduced rapid medium to heavy throttle the car stumbled, but under a light steady throttle it revved perfectly. This leads me to believe the fuel pump is dying and is already maxed at idle and anything more than a light throttle makes it difficult for the fuel pump to keep up with demand.
So if you read through all of that my question is simple, those of you who have a tuner or can data log can you tell me what your fuel pump duty cycle is at idle and under load? Also at what point does it go to 100%? The car is not heavily modded, only a JLT air intake, O/R X-pipe, flowmaster catback, and the tune is setup for these mods. The tune is not the issue because I just installed the X-pipe and tune today and the car actually improved.
So if you read through all of that my question is simple, those of you who have a tuner or can data log can you tell me what your fuel pump duty cycle is at idle and under load? Also at what point does it go to 100%? The car is not heavily modded, only a JLT air intake, O/R X-pipe, flowmaster catback, and the tune is setup for these mods. The tune is not the issue because I just installed the X-pipe and tune today and the car actually improved.