95 GT throwing code 312


New Member
Feb 28, 2010
I recently purchased a 95 GT that is bone stock as far as the engine goes. The idle was rought and it was throwing lean codes for both banks, but I've cleared the codes up with a new MAF sensor. It runs a lot better, but now the idle is high (even after resetting the idle) and it still has a slight misfire at low RPM's. I've checked everything for vacuum leaks and can't find any. Now it finally started throwing a code 312 when I do a KOER test. This apparently mean the AIR system isn't being diverted. Would this cause the high idle/misfire? Also, how the heck does one go about fixing this?

Thanks in advance!
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If I had to guess, I am guessing that you have a vacuum leak. Check the hard plastic hoses going to the smog system. If cracked, replace them (or just rip it all out and plug them off).

The key is that, whether you have the smog system or not, you need to make sure those vacuum lines are not leaking.
Jeff's advice sounds good to me. The TAD is inside the passenger fender (remove the wheel and fender liner to access it).

Good luck.
take a can of carb cleaner and spray it at different hoses while it is idling. when you spray near a vacuum leak, the idle will change.

there are a couple hoses behind and under the upper intake that are hard to see
Sounds like good advise. I've already doused the intake/throttle body and engine compartment vacuum hoses in carb cleaner, but I guess the next step is opening the fender and working from there. I'm going to do this tonight, so hopefully I can trace the problem. This has been driving me nuts for 3 months now! :(