Freshly rebuilt 13b It starts but once it starts it jumps to 2500 rpm sits there for about 5 secs then shutoffs and backfires. Anyone have any ideas? Also its in an FC 88.

 

I'll be the first to bite. Have you checked for vacuum leaks with a smoke machine, is the AFM plugged in, and is the car stock or if modified what's been done to it?

 

I havn't check for vac leaks with a smoke machine but all are capped off(that arent used) rest are hooked up blockoff plates are sealed with red rtv, afm is plugged in, Its a s4 keg with s5 front and rear iron. Did notice that my pressure regulator wasnt plugged in but when i hooked up the vacuum line it didnt make a difference bad pressure sensor maybe?

 

The reason why I specify a smoke machine is because I had a feeling you had probably performed an emissions delete with caps and block offs. Even with the RTV it's very common for the block offs to leak, not to mention those are not the only possible locations for a leak. Sounds like you're assuming all is sound. I'm not saying that's your issue, but we see a lot of cars where the owner swears it's all good and come to find out a week later a massive vacuum leak is discovered

 

I'll try that. It has the emissions deleted along with the rats nest and the 5th and 6th port opened. Has the bac deleted and blocked off along with the OMP and the actuator on the LIM. Quick question (its been awhile since I had my motor) does any electrical plugs by the pressure regulator get plugged into the main engine harness?

 

or many leaks. in fact i see vacuum leaks so commonly that people should never assume anything they did was 100%.