Hello everyone! here with my ‘91 c1500 350 sbc tbi. Just wondering if elevation has a huge impact on how the truck will run when changed? I read on a couple forums that it uses the O2 sensors to help with air fuel mixture. I’m not sure I read a lot of different replies. If anyone knows or has an idea let me know! I’m planning on taking the truck up camping and I’m going to climb about 2 thousand and some feet!

 

Short answer is yes, the truck will run but there will be a noticeable decrease in performance not huge but it wont be the same. Elevation does play a role in how your pcm controls your A/F ratio. Its not a must but I would plug a scanner into the truck and make sure your o2 sensors arnt throwing any codes and preforming as usual along with your maf sensor.

 

FYI a 1991 will not have a MAF (Mass Air Flow) sensor. That didn't come out until the 1996 model. Prior to that there was a MAP (Manifold Absolute Pressure) sensor, but it doesn't really measure air quality or O2 - just the intake manifold pressure. I am sure the MAP and O2 sensors need to be operating properly of course, as if they are not, the PCM probably makes assumptions that it is running at sea level air pressure.

 

Thats my fault I thought it said 97 not 91. I was going off basis of my 97 350 tbi.

 

If I remember correctly on your 91 C1500 w/ a 350 VIN K, the MAP sensor doubles as a Barometric pressure sensor to adjust for altitude.