Stalling when reaching boost or 0 vacuum

[LunchboxCritter]

I have recently swapped my 91 USDM NA to a S5 Jspec TII. It has a 3" downpipe and I'm still scrounging to get an exhaust. As it sits it'll drive and move around. I hooked a boost gauge up to monitor the pressure. When given more than half throttle it'll reach zero vacuum and the car will stall. Is this caused from lack of backpressure from an exhaust, rear rotor fuel cut, or what? Any and all suggestions would be greatly appreciated.

[FerociousP]

does it have a turbo ecu, map sensor, and maf sensor?

[LunchboxCritter]

Yes it has all of those, rather they are all in correct working order I don't know. The ECU is the J-Spec (N374 I think). I installed a chip from SpeedLabs into it before beginning the swap in hopes of avoiding some of the problems that I had read about before hand. I also removed emissions (split air pipe, and air control valve, I kept the BAC) and removed the rats nest.

With the ACV gone I connected the map sensor to the nipple under the BAC valve, next to the large vacuum for the brake booster. Could this be the problem? If so where is the best place to connect it?

[Max777]

there is supposed to be a "restrictor pill" in the hose to the turbo MAF... but I ran my car w/o one for a while untill I could get one ordered. Not sure if this might affect anything though, seen people point it out here and there.

[RETed]

Unplug the electrical plug on the boost sensor and carefully drive around and see if the problem changes.
This will eliminate the boost sensor or boost sensors readings back to the ECU.


-Ted

[LunchboxCritter]

Thanks Ted I'll try that in a little bit and let you know what happens.

For Reference here is how my setup is right now.

[LunchboxCritter]

I unplugged the pressure sensor and started the car, it didn't seem to make any difference either way. It still stalled when it reached neutral pressure.

[RETed]

Okay, you've eliminate the boost sensor being the problem and also possibility of overboost fuel-cut.

Basically you're down to the TPS and / or airflow meter...

Have you checked the TPS yet?
Specifically, does the TPS spec out linearly with no jumped in resistance?
http://fc3spro.com/TECH/HOWTO/TPS/tps.html


-Ted

[LunchboxCritter]

Thanks Ted,
I checked it the tps in "neutral" it was 1.78 ohms and WOT it was under 5 ohms. Seems to sweep clean as it increased. I adjusted it down to 1.1 ohm and now the car idles around 1500 where it was at 1000. Still stalling at half or greater throttle. I'll adjust it back. My BAC doesn't have an adjustment screw and the throttle adjust is barely contacting the throttle (best I can tell it's backed as far off as can be and still making contact). Not sure how to check the AFM.

[Max777]

checking the AFM:

go here: www.Foxed.ca go to :rx7 manual, then find the fuel/emissions controls section.... from that find AFM test


Or if you've got an S4 turbo, go here: (resistance values MIGHT be different on N/A and S5)

http://foxed.ca/rx7manual/manuals/19...TEMS_TURBO.pdf

[LunchboxCritter]

okay I tested the Air Flow Meter. It is good. I turned the speedlabs chip around, and eliminated that as the problem. It would only start with the chip one way, not the other. I'm thinking that I need an N370 ecu to at least try in there. Any more suggestions? Thanks everyone for all of your help and suggestions.

[LunchboxCritter]

Update:

Checked the AFM = Good
Ghetto Compression test = Good (all 6 puffs over 100 psi)
N374 ECU = still suspect

any more suggestions? Thanks for all of the help so far.

[RETed]

Tried scanning for error codes?


-Ted

[LunchboxCritter]

Ted, I'll check that out in a few. Looking for an n370 ecu to try in there.

[LunchboxCritter]

Update: I found an ecu. It's on it's way. I'll let you know if that fixes my problem. Thanks for all of your help.