robshil6

Ok its a 1988 Gta 5.7L Forgot to add TPI. I get a code 34 i know low voltage on maf. Here the weird thing when i got the car the tank was leaking. I replaced tank then started getting code 34 once and awhile when car was restarted on long trips. disconnect battery cable most times it would clear code never ran bad during this time. I Have the dealer book and tested out maf curcuit tested fine i replaced maf. Had the same problem so i changed cpu still didnot help. So i just lived with if for like 3 years.Just bought a set of injectors mine were leaking down replace them car was great started right up no problems then four days after code 34 shows back up. but know when the code shows up after awhile of driving like before but now has a rough idle. clearing codes does not help now. i did unscrew gas cap and it went away. Dealer told me there not intrested so im lost. Thinking has something to do with gas pressure in tank thinking canster not working right or something ok thanks in advance rob

robshil6

Belive I got it fixed!!! there is a small tank pressure valve right before the canister this is vacum operated. But also pressure in the tank opens it to put fumes in canister. so no more code 34 and no more pressure in tank Yeaaaaaa!! 20$ from autozone

camaro1185

I have a simialr problem. Did you smell gas after the car was shut off?

What is this valve you speak of, and where is it located. Is it the white one that drops infront of the rear axle?

Could you be more specific of what you replaced (pic maybe?) so i can check mine?

robshil6

no smell of gas just real high tank pressure! The valve is under the hood pass side near the charcoal can. It connects to the metal vent line from the tank to the valve then to the canister! and the one by the rear tire is supposed to let air in not out it is used so there no vacum in the tank. If you take it out shoud be able to pull air through it but not push it out. if that is not working right will smell gas