PROBLEM: My car stumbles above 5000rpms at 10.9 psi with the afr set to 11.5-11.9.

SETUP:
-Tech Edge 2b0 wideband, latest firmware/software, digital display and datalogit out -readings match. The unit is grounded directly to the battery.
-Bosch 5 wire 7054 sensor with less than 2,000 miles on it. The previous sensor had about 10,000 miles on it and gave me the same readings. I have tried recalibrating both.
-Leading Coil: 20,000 miles verified to be in good shape by the previous owner (ie ran 14lbs without an amp. Prior to that I was using my original coil with 70,000 miles. I had the same problem with both.
-Plugs: Stock 9s all around with less than 3,000 miles on them
-PFC
-Ignition amp: none
-Ground straps galore.
-See sig for the rest of the mods

ADDITIONAL INFO:
-voltage in the datalogs is 14v about 98% of the time and occasionally drops to 13.8, but there is nore correlation between the drop and stumble.

I've been chasing this problem for a long time, so any help will be appreciated!

 

every gear?

do you have an early 93?

old harnesses have a ground terminal near the coil packs...if you have this GND, try removing it.

 

EDIT: This is CCarlisi. 3rd, 4th. It's a 94 but the harness does have that ground.

 

I get you mean about stumbles, but in what way..?? hesitation, ign breakup, no power?

 

car is fixed. b10egv's in leading.

 

Changing the plugs solved the problem. I didn't think that was an issue because the problem started with 10.5 NGK plugs installed. I pulled the 10s and the electrodes didn't look worn, but I switched to a new set of 9s just to be safe and the problem didn't go away. Based on that I ruled out the plugs. Fortunately Rich was convinced the problem was the plugs and pushed me to swap them out again.

I'm now running at just under 15psi with the afrs at 11-11.5 and the car feels great.

 

Yup, car pulls like a bat out of hell, nice and smooooth, wants to rev past 8k too. Ready to make some timed datalogs chris ?

 

Not until I get my ignition amp back so I'm certain I can spank your ***