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.

http://i313.photobucket.com/albums/ll384/LunchboxCritter/Engine%20Swap/VacCurrent-1.png

[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/1988FSM/04b_FUEL_AND_EMISSION_CONTROL_SYSTEMS_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.

[LunchboxCritter]

Update: Installed n370 ecu and now I've got boost. I have to get the idle adjusted right and I'll be in great shape. Thanks everyone for all of the help and suggestions.

[MazdaMike]

I would lean towards the ECU I would try a US spec turbo ECU.

[LunchboxCritter]

Update: I have installed an n370 usdm ecu. woo hoo car makes boost now.

Question: On the J-Spec fuel rails does the fuel flow go in the secondaries and return out the primary rail (opposite of usdm)? The primary rail on the j-spec doesn't have the pulsation damper like the usdm rail.

[Gregory Casimir]

the jspec ecu that you had, was it a chipped one?

[LunchboxCritter]

yes, the N374 is chipped with a speedlab performance chip

[LunchboxCritter]

Here is a picture of the fuel rails. Right now I have the primary going to the fuel filter and the secondary going to the return. I believe that is backwards for this j-spec setup. Could someone please clarify?

http://i313.photobucket.com/albums/ll384/LunchboxCritter/Engine%20Swap/DSC01113.jpg

[FerociousP]

the regulator (top right with the vac hose) is at the end of the fuel loop. The return line should be coming off this and go back to the tank. If you have them hooked up wrong I doubt it run at all.. With that said, I'm pretty sure you have them hooked up correctly as long as you know which rail in the primary and which is the secondary.

[LunchboxCritter]

Secondary on the top, Primary on the bottom. :)
Thanks for the info. I'm relieved not to have to remove the UIM again.

Car runs okay, idles sort of funny. Clutch to the floor and it'll idle right around 1000rpm let off the clutch in neutral and it drops to around 750-1200 or so and just bounces between the two. TPS is set as close to 1.0 ohm as I could get it. BAC checked at 11.9 ohm (so I assume it's good).

[LunchboxCritter]

One more tech question. My speedo isn't working, I think it may be the speedo gear in the transmission. I have the NA one from my old set up. Will it work in the TII transmission with the rear end gears being different would it be at all accurate?

[Ender]

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.

http://i313.photobucket.com/albums/ll384/LunchboxCritter/Engine%20Swap/VacCurrent-1.png

Why is your charcoal canister hooked into your turbo inlet duct? That's unnecessary, if not creating a vacuum leak.

[LunchboxCritter]

That could be why I'm having problems getting it to idle correctly. Where should that side of the charcoal canister go, can it be vented to atmosphere?

Update: figured out I have my fuel lines routed behind my speedo cable, and it's causing it to pull off the back of the speedo. Going to reroute it back behind them and speedo problem will be fixed.

[Ender]

It's supposed to treat the fumes from the gas tank, and then I think it normally vents to the atmosphere anyway, but I think they sometimes clog, get too old, or do something wrong and make your car smell. So I said screw it and pulled my charcoal canister out completely.

[LunchboxCritter]

Mystery Solved: Idle problem was caused by the neutral safety switch not being hooked up to the right wires. Figured that out and corrected it, then adjusted the tps and idle set screw, now I've got a 800 rpm steady idle in neutral (with & without clutch pressed). Thanks everyone for all of your help/suggestions.

PS: I tinkered with the charcoal canister and decided it was best hooked up the way that I have it. I found it actually idles better hooked up than with it being unhooked. I don't know why, but I'll leave it alone. It's not creating a vacuum leak from what I can tell.

[Gregory Casimir]

so the way you have it set up then is the correct way? I should be finishing up my swap this week or so. I really would like your help on this!

[LunchboxCritter]

so the way you have it set up then is the correct way? I should be finishing up my swap this week or so. I really would like your help on this!

I do not know for sure if it's the correct way or not. My car is running great, boosting at 9 psi, idling at 800 rpm, and holds 18 psi of vaccum at idle. This vaccum diagram is how I currently have my vaccum and emissions stuff ran. Hard to tell from the diagram but I have the one way check valve on the charcoal canister so it can only pull the fumes into the intake hose, rather than blowing air into the charcoal canister. If I can be of any help just let me know.



http://i313.photobucket.com/albums/ll384/LunchboxCritter/VacCurrent-1.png

[Bigshanks2002]

my 91 JDM S5 is doing the same thing. it seems as though the secondary injectors might not be kicking on. The main realy switches power to the 2 primary and the two secondary injectors individually. You need to start the car and pick up the idle to about 3000rpms and listen with a stethoscope (or a long screw driver to your ear) to see if the secondary injectors are ticking.

[RETed]

The main realy switches power to the 2 primary and the two secondary injectors individually.

Uh...no.


-Ted

[LunchboxCritter]

my 91 JDM S5 is doing the same thing. it seems as though the secondary injectors might not be kicking on. The main realy switches power to the 2 primary and the two secondary injectors individually. You need to start the car and pick up the idle to about 3000rpms and listen with a stethoscope (or a long screw driver to your ear) to see if the secondary injectors are ticking.

That's not it, I figured out that I had the neutral switch wired up wrong. That was causing my problems.

I am now wondering if my chipped ecu wasn't in "limp" mode because of wiring mistake. If so, why would the N370 not have entered "limp" mode as well?

I'm considering throwing the n374(chipped) back in there and see what it will do now that the neutral switch is wired right.