Smedus07

I recently swapped a 02 5.3/4l60e in my 85 chevy pick up. All stock besides tuned (sent off computer, did not have it tuned after I stall) and long tube headers. At first I started it without the 02s hooked up and it ran fine down the road but was very hard starting even after it was warm. Later that I week I installed new 02s ( only tuned for 2). After installing the new 02s I noticed the truck started as it should but after maybe 2-4 mins of driving it would lose fuel pressure on one bank to the point that the motor would die. The fuel pressure issue was diagnosed thru a friends scanner. I unplugged the maf sensor and truck ran exactly as it did when the 02s were unplugged. So I changed the maf sensor and got the same results as the previous sensor.

So did I buy 2 new junk 02s?
Are my long tubes giving me tuning issues?
Did I buy a new junk maf?
Or is this a tuning issue or something else I'm not seeing?

Old Geezer

iTrader: (3)

" After installing the new 02s I noticed the truck started as it should but after maybe 2-4 mins of driving it would lose fuel pressure on one bank to the point that the motor would die. The fuel pressure issue was diagnosed thru a friends scanner."

How is the scanner showing bank to bank fuel psi?

a05c

Without using a mechanical gauge to check fuel pressure I wouldn't trust the scan tool.

I personally have never seen a bank to bank fuel pressure reading, especially on a stock application.

If its losing fuel pressure, is it under load? just idling?

When was the last time the fuel filter was changed?

Which O2 did you put into the header? (front or rear) Did you turn off the rear O2's? disable catalyst monitor checks in the PCM?