Misfire like fuel cut under throttle - Stumped!

[TwIzTeD_3kGt]

PTU also had no effect.

Seems just past 3k is the problem, and it doesn't like any RPM above that. What's throwing me off is that WOT in 1st gear is fine.

Another thing to note, my front O2 sensors do not want to read at idle. They both sit at 0v at idle, which makes the fuel trim for the front hit 12.5%. Rear O2s both cycle at idle no problem, and their fuel trim is 1% for low and mid. If I drive or hold the rpm at 2000rpm, the front O2's will slowly start reading, and then fuel trims go back to where they should. As if maybe the front O2 heaters weren't working. It did this for both the old and new sensors. Not sure if this would lead to the problem I'm having, but it wasn't a problem in the past. Possibly a problem with the harness going to the front.

[DK77]

OK, I wasn't sure where the tach signal originated, I just was pretty sure it wasn't the crank sensor.

[DK77]

Another possible culprit that I just thought of, what about the TPS?

[KeithMac]

Did you pull the pump hanger and check the pump (o rings can split).

I would replace the fuel filter just to rule it out.

You need to view fuel pressure in real time, while under load to have a proper baseline.

[TwIzTeD_3kGt]

TPS shows consistent on the logs. I did not pull the fuel pump completely out, but there are a few reasons I don't think I'm running out of fuel: The A/F goes rich as it should throughout acceleration until it hits limp mode. I can WOT 1st gear and it will hit limp mode at 5500rpm. If I half throttle 1st gear (much less fuel & spark needed) it hits limp mode at 5500rpm.

With some help from Jester, and changing some peripheries, the O2's are all now online. BUT on the logs, they keep exceeding 1 volt while cycling. Like 1.2v, 1.3v. Shouldn't be possible, and I don't think a wire short would cause a .3v increase in readings only while cycling. More like ECU in my mind, anyone run into this? Oh, and the problem is still the same.

[RealMcCoy]

^^^ get a volt meter on your sensor ground and see if you have a small amount of voltage riding on it. I'd also verify the O2 voltages in case of a logger scaling error.

When you guys were tuning your cars, did you do anything with the low octane maps? I'm just wondering about knock or knock sensor issues sending your tune out to lunch if the low octane maps are off.

[TwIzTeD_3kGt]

Ill check out the sensor grounds.

For the low octane maps I previously just used the high octane map minus half an afr point. I've been logging the octane level and it stays at 100, so it isn't trying to reference the low octane map as far as I can tell.

[DK77]

Ray tuned my car so I'm not sure about the low octane maps. It's something I'll check if I continue to have problems after I replace the sensors (if I ever have time lol).

[TwIzTeD_3kGt]

Problem is gone. Not sure what fixed it because I did a few things at the same time.

One, I found .11-.14v on the grounds of the front and rear upstream O2 sensors. No voltage on the cam/crank sensor and knock sensor grounds. But .16v on the TPS ground. Significant or no?

I noticed at throttle closed the TPS was reading 14.1%. It has always read 13.7% for as long as I could remember. I had already noticed this before but thought nothing of it. But since I was grasping at straws, I adjusted it down to 5%.

Lastly, I moved all the wiring in the engine bay quite a bit. All the wires held down by those flexible anchors on the trans, I release and tugged on.

Went for a drive and the problem was gone.

It does have a new issue though. If I just crack the throttle open, it doesn't want to do anything. Just goes lean like decel fuel cut and doesn't go anywhere until I give it more throttle. Coming out of decel fuel cut while driving is also very noticeably harsh/sudden. I'm thinking the TPS may have been the main problem and the cause of this new problem?

[RealMcCoy]

At 5% your idle switch is probably opening about 1/2 throttle, you need to go back and fix that... The TPS is adjusted by where the idle switch opens, not buy the TPS percentage. I would expect that is the cause of your new issue.