2000 gt. I just rebuilt this motor for a friend. It was down for two months. The motor came out of a 2002 gt that I rebuilt. I rebuilt it stock, the only mods are a bbk 70mm throttle body and a CAI. The motor that came out of the 2000 was to far gone to rebuild, but the throttle body and the CAI were on the car already before it blew up. Does it need a tune now? I'm thinking that it possibly had a tune before, but having the battery out for two months reset the computer. It is giving me codes p0171 and p0174. The car idles fine in park, but the minute I put it in drive it wants to stall out and does stall. It has a new iac and I took the maf off of my 01 gt and no change.

 

You need to look for vacuum leaks and any possible sources of unmetered air being drawn in.

Start at the plenum and follow every line coming from it, pcv lines, etc. A can of carb spray can be helpful; with the engine idling give small blasts of it at any areas you suspect; any changes in idle (generally increases) will confirm a problem area.

Highly doubt it needs a tune for a cai and tb, at least as far as this issue goes. That's more of a S197 3V engine thing.

 

I was able to get the stock throttle. I put it back on and it made a huge difference, no more bucking when driving. It still has the issue of wanting to stall out at idle in drive. I have sprayed everywhere with throttle body cleaner and can't find any vacuum leaks. I'm going to scan it tonight when I get home.