Engine High AFR / exhaust backfire on one side of exhaust

Hello,
I have recently rebuilt my engine and am having an issue with my AFR. The A side runs around 13-15 AFR except during WOT. The B side is consistently 0.5-1.0 AFR higher than A side during the first 10 minutes of driving, but after those 10 minutes the B side of the exhaust is reading 15-19 in gear and up to 20 AFR during idle. Also after the 10 minutes of driving, there is popping in the exhaust especially during times where I am pushing on the clutch or have the car in gear without pushing on the gas pedal. This only happens on the B side.

I have tried:
Check for exhaust leaks - there was one but it only improved the AFR by about 1
Checked vacuum hoses - all are connected and are new silicone hoses
Swapped the A & B wires connecting O2 to the gauge - no effect
Replaced the wide band sensors - no effect
No smoke except a small puff on startup
Visual inspection shows that both mufflers have turned yellow/gold and have spots that are blue/purple, but the rest of the exhaust is higher quality and is unchanged


Codes:
P0150 (pending) - O2 sensor circuit (bank 2 sensor 1)
P2198 (pending) - O2 sensor signal biased/stuck rich (bank 2 sensor 1)
--there was another code that I saw once for lean but never saw it again--
There are usually no codes but sometimes one or both of these two appear. They are very inconsistent appearing at random times. Sometimes one code appears but other times both appear and they never become "confirmed." If I clear them they don't appear until sometime after the engine starts having high afr/backfires

I've tried researching my specific situation but I cannot find any information on this exact problem.
Any insight would be appreciated, thanks.


Relevant parts:
ENGINE: 331 w/ dart block, edelbrock intake, afr 205 heads, scat 331 rotating assembly, 70mm accufab TB, Anderson CAI, 75mm Pro-M MAF, Pro-M ECU OBD-II, 30# bosch injectors, bbk fuel rail, stock fuel pressure regulator, silicone vacuum lines, 255 lph fuel pump, canton oil pan w/ pump, Smog delete, MAP delete

EXHAUST: BBK shorty headers, BBK cat H pipe, Walker quiet flow muffler

AFR: DLG-1 dual lambda AFR gauge, Bosch wide band sensors
 
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MAP delete? Mass Air computers didn't have a MAP sensor, they had a BARO sensor. Delete it and you have no way to compensate for changes in barometric pressure due to weather or altitude.

What year car? What kind of computer - OBDI or something else? Truck computer? What is the code for the computer?
Only OBDII computers had one alphabetic character and 4 numeric characters.

The codes don't fit the Fox 5.0 format of 2 digits for all computer equipped Mustangs before 1994.
The 94-95 had 3 digit codes but they are all numeric, no alphabetical characters.
 
Its a 1993 GT so yes it was a BAP sensor delete and not a MAP sensor. The delete for BAP was done because I did an ECU swap to Pro-m's foxbody OBD II ecu and the instructions on LMR.com and Pro-M stated the BAP or MAP was to be removed.
Since its an OBD 2 swap, the codes are generic OBDII codes that I can read with a scanner or by plugging my computer w/ tuning software into the ECU.
P0150 (pending) - O2 sensor circuit malfunction (bank 2 sensor 1)
P2198 (pending) - O2 sensor signal biased/stuck rich (bank 2 sensor 1)
 
Its a 1993 GT so yes it was a BAP sensor delete and not a MAP sensor. The delete for BAP was done because I did an ECU swap to Pro-m's foxbody OBD II ecu and the instructions on LMR.com and Pro-M stated the BAP or MAP was to be removed.
Since its an OBD 2 swap, the codes are generic OBDII codes that I can read with a scanner or by plugging my computer w/ tuning software into the ECU.
P0150 (pending) - O2 sensor circuit malfunction (bank 2 sensor 1)
P2198 (pending) - O2 sensor signal biased/stuck rich (bank 2 sensor 1)
Those are very important clues that were missing from your first post.
It is very difficult to relate your problems to the ordinary computer system that is in stock Fox body Mustangs.

The BAP sensor is inside the computer on some of the OBDII Ford computers, so bypassing the externally mounted BARO sensor makes sense.
 
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You try calling pro m ? No offense there is a reason why guys dont commonly use this system when going stand-alone . Which also I believe uses the stock harness still the whole point of a stand alone is deleting the 20 plus year old engine wiring .

Either way pro m is going to be your best troubleshooting bet .
 
Its a 1993 GT so yes it was a BAP sensor delete and not a MAP sensor. The delete for BAP was done because I did an ECU swap to Pro-m's foxbody OBD II ecu and the instructions on LMR.com and Pro-M stated the BAP or MAP was to be removed.
Since its an OBD 2 swap, the codes are generic OBDII codes that I can read with a scanner or by plugging my computer w/ tuning software into the ECU.
P0150 (pending) - O2 sensor circuit malfunction (bank 2 sensor 1)
P2198 (pending) - O2 sensor signal biased/stuck rich (bank 2 sensor 1)
My best guess is that the passenger side front O2 sensor harness has a bad connection or broken wire,
OBDII cars typically had an O2 sensor in front of the catalytic converter to measure A/F ratio and one after the converter to measure it's efficiency.

Measure the O2 sensor voltages at the computer with the engine running at idle and then at about 1200 RPM.

I would give you the connector pin numbers but they are only correct for the stock 5.0, Fox body computer. You'll have to check with Prom-M to get the information for your computer and wiring harness combination..

Use the ground next to the computer to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.

Testing the O2 sensor wiring harness
Most of the common multimeters have a resistance scale. Be sure the O2 sensors are disconnected and measure the resistance from the O2 sensor body harness to the pins on the computer. Using the Low Ohms range (usually 200 Ohms) you should see less than 1.5 Ohms.
 
Hello,
I have recently rebuilt my engine and am having an issue with my AFR. The A side runs around 13-15 AFR except during WOT. The B side is consistently 0.5-1.0 AFR higher than A side during the first 10 minutes of driving, but after those 10 minutes the B side of the exhaust is reading 15-19 in gear and up to 20 AFR during idle. Also after the 10 minutes of driving, there is popping in the exhaust especially during times where I am pushing on the clutch or have the car in gear without pushing on the gas pedal. This only happens on the B side.

I have tried:
Check for exhaust leaks - there was one but it only improved the AFR by about 1
Checked vacuum hoses - all are connected and are new silicone hoses
Swapped the A & B wires connecting O2 to the gauge - no effect
Replaced the wide band sensors - no effect
No smoke except a small puff on startup
Visual inspection shows that both mufflers have turned yellow/gold and have spots that are blue/purple, but the rest of the exhaust is higher quality and is unchanged


Codes:
P0150 (pending) - O2 sensor circuit (bank 2 sensor 1)
P2198 (pending) - O2 sensor signal biased/stuck rich (bank 2 sensor 1)
--there was another code that I saw once for lean but never saw it again--
There are usually no codes but sometimes one or both of these two appear. They are very inconsistent appearing at random times. Sometimes one code appears but other times both appear and they never become "confirmed." If I clear them they don't appear until sometime after the engine starts having high afr/backfires

I've tried researching my specific situation but I cannot find any information on this exact problem.
Any insight would be appreciated, thanks.


Relevant parts:
ENGINE: 331 w/ dart block, edelbrock intake, afr 205 heads, scat 331 rotating assembly, 70mm accufab TB, Anderson CAI, 75mm Pro-M MAF, Pro-M ECU OBD-II, 30# bosch injectors, bbk fuel rail, stock fuel pressure regulator, silicone vacuum lines, 255 lph fuel pump, canton oil pan w/ pump, Smog delete, MAP delete

EXHAUST: BBK shorty headers, BBK cat H pipe, Walker quiet flow muffler

AFR: DLG-1 dual lambda AFR gauge, Bosch wide band sensors

Phillip did you ever get this fixed I'm having the same issue?
Thanks
Josh