Ok guys I am in a major bind. I have a 1989 Firebird that was a 305 TBI that with the help of painless and a few others I have converted to a 350 TPI. Everything is set up correctly and I have an ASE mechanic helping me on this but we are at a block.

Here we go:
The problem we are having is that the car cannot be run for more than 5 minutes or the exhaust cat gets cherry red and almost catches fire. The computer is ahowing a code 33 which says there is a problem with the mass airflow sensor. We have disconnected the the sensor which should put the computer into a default mode and we attain the same red cat. For whatever reason we thought maybe the EGR was a problem, but it was disconnected with the same result. For you spec guys here are some:

At idle I have the following:
-Fuel pressure is 45 PSI, but there is an adjustable regulator so it can be changed.
-TPS switch reads .08 at idle and 4.8 at wide open throttle.
-The mass air flow sensor reads 3.92 grams per second at idle
When checking the voltages on the terminals on the mass it shows the "C" terminal reads 5volts and the "D" reads 0 volts. Both "A&B"terminals are grounded correctly. This is a Bosch Mass Air Flow sensor.
-Timing is currently set at 0 degrees but has been adjusted to +6 degrees and we have the same result.
-The computer is a re-man unit with part number 1227165R and a street chip from Motorvation.

Everything points to the Mass Air FLow Sensor but the same problem exists in default mode!!

Please guys any help would be appreciated.

Thanks for ya'lls time

Wayne

 

MAF relays more than likely. Also, how old is the cat itself? May be partially clogged or your timing is off allowing burning of fuel in the exhaust.