Stumbling under hard acceleration, throws codes and performance fails spectacularly

[Devin]

So I've now had this happen twice, and it is the same exact problem each time. It is really scary too, as it always happens on the highway.

When I put my foot into it, on rare occasions the car will all of a sudden stumble, throw a CEL for less than a second, and then within minutes it will start acting up. And by acting up mean I can't keep going 60, then I can't sustain 50, 40 30 20 or even 10. If I let it sit for an indeterminate period eventually it will run again, but I've now hit this problem twice.

The CELs are:
(KOEO Hard Codes)
21 - Cooling Temperature Sensor out of Range
24 - Intake Air Charge sensor or Vane Air Temperature sensor out of range
(KOEO Continous Memory codes)
49 - SPOUT signal problem
56 - Mass or Vane Air Flow sensor above maximum transmission sensor failure
55 - VAF-Mass air flow sensor fault, below minimum voltage

This is way over my head, could all of these sensors be bad?

 

[rubydist]

I have never seen a SHO run right with the iat temp code.

the fact that you also have a mafs code suggests that you may have a connector and/or wiring issue on that segment of the wiring harness, since they use a common ground, iirc.

I would start with tracing all of that section of wiring and make sure all connections are good.

 

[Devin]

So is that doing continuity tests from the grounding pins to the body?

 

[NealVA61]

If you've had the intake plenum off for any reason check all bolts and connections.

 

[Devin]

Many, many times. I'll check.

Would oxidation on the bolts / brackets contribute?

 

[NealVA61]

When I had a similar problem with my '95 ATX it was specifically the 2 bolts on the crossover tube. I apparently failed to tighten them. Also check to make sure that the ground strap at the rear of the plenum (same side as crossover) is tightly connected.