S5 Six Port Bridgeport Running Issues After Rebuild
 

First off, I might be crazy for even thinking that this would work but those freakin' Youtube movies made me think I could!

All that aside, I've done some searching on this subject and I have tried several things but I think it may be above my knowledge. I've been working on this car for two years now and I'm so close!!

The car is a 1991, S5 N/A Six Port 13B that has the AUX sleeves removed, mild porting on the primary ports and a bridge on the secondary ports. The AUX ports are just smoothed a bit. I've seen a few Six ports with far more aggressive porting than mine that seemed to run rather well with just the factory ECU. I am also running the factory ECU, a Jacobs FC1000 ignition amp, Walbro 255, factory fuel rails, brand new injectors (all 440cc) with an AFC Neo for smoothing the maps out. At least I had hopped so.

I can get the car started but I'm having trouble keeping it running. I know with the insane amount of air with all six ports open and the porting that there would be a need for a higher idle. She'll brap brap at around 3,000 revs just a bit but I have to hold the accel down. Once in a while while holding revs, there will be some rather aggressive popping and backfire. I'm guessing it's the timing being incorrect and the ignition is trying to advance? I've fiddled with the Crank Sensor, cleaned plugs every time, double checked wiring, fiddled with the throttle body, double checked for vacuum leaks and I'm still at a loss. I haven't touched the AFC map thinking that it should at least run somewhat without any corrections. Maybe I'm wrong.

When I got the car, it wasn't running, so, could it possibly be a TPS? Bad Crank angle sensor? MAP sensor? I don't know. I can't prove that any of these sensors worked properly before I got the car and I assume like most factory ECU's it has to learn a little bit before it runs properly. I wish I knew more about these kinds of things. I'm getting a little discouraged now and have almost considered selling it as is but as Spring gets closer, I keep thinking about hearing that brap brap at a stop light with the sunroof open.

Any help you guys could give me would be very welcome!

You need to add fuel for it to even idle.

Bridgeports require more fuel then you can imagine. With my small bridge, 2.5mS on 720CC injectors at 40 PSI of fuel pressure keeps it idling at 13.5:1. The stock ECU tries to idle at around 1mS on 460CC injectors at around 35 PSI of fuel pressure.

Add a shed load of fuel with the Neo, or swap in 550CC injectors all the way around.

Either way it won't run well with the stock ECU because you won't be able to give it the timing or split it needs. The S5 intake won't work very well for this.