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

 

First get the MAF working properly. Here are a few charts courtesy of Trickster. Make sure you follow every step to the letter.

 

Number 2

 

I appreciate the help, however we have been through all of those diagrams and everything is working as it is suppose to. We are wondering if something as simple as a clogged cat could be causing the problem. I will be working to see if this is the it, and getting back to ya'll soon. Keep thinking guys, we need all the ideas you can find.

Thanks again,
Wayne:hail:

 

Am I reading this right? The TPS should be between .54 and .64 at idle.

 

This screams clogged catalytic converter...

 

Yup. Red or glowing cats usually points to the cat being clogged. Obviously, the more it glows, the more it's clogged.

 

Thanks again guys, ya'll are the best. We are in the process of testing the cat, I'll get back to ya as soon as I can and let you know. I'll also double check the TPS sensor to verify

Thanks again!
Wayne

 

FWIW, if it wasn't glowing before the swap, it may not be clogged.

Have your buddy check exhaust backpressure, if it's good, then I'd suspect you're dumping way too much fuel in the motor, or the timing is really late.

 

For those still watching this post here is an update: Do you know that when an ECM is "rebuilt" it is only bench tested?? Basicly in a TPI set up there are what is called 4 quad-drivers that control the rate the fuel is dumped from the injectors to the motor. When something happens to the ECM, 9 out 10 times, all the quad-drivers are either damaged or made inoperable. What the rebuild companies do is replace the inoperable ones, not the damaged ones. Therefore when it is bench tested it works fine, but in a car you may get a Code 33, or MAS error. This was my problem! I found an ECM with quad-drivers that were working, replaced the damaged ones and the car is fine now!! Think about this the next time you have this kind of problem!

 

Yeah but after finding out this. Isnt your cat still toast...it would appear to be if the shell had gotten red lets just imagine what the inside looks like?

 

I am not sure if the Cat is toast. The car seems to run just fine, however I do plan to replace the Cat in the near future. At this point everything is working fine except the gauges, but that's another post for another forum! Thanks for ya'll's help, and I'll keep ya posted