unek87

ok well im trying to install a bac on to my s4 na-t . the harness is messing the wiring so i want to just run new from the ecu . pin 2Q is voltage from what my pin out diagram says . now the ground could i just run a ground to a good spot on the motor ? thanks guys

satch

iTrader: (1)

The B/W wire is voltage w/key to on which is the wire that supplies voltage to the BAC, and the wire connecting to pin 2Q is the ground wire and it will have battery voltage on it when the BAC is not being used and when the ECU suggests to the BAC that it should be working the voltage on this wire drops and the more it drops the more the BAC works as far as opening up more and allowing bypassed air to enter the manifold.

unek87

ok well my wires are not there so i am gonna run from the ecu 2 new wires . so the b/w what exact pin is that . and the blue wire is 2q from what i see . thanks man for the help . i've read so many threads today on idle and the bac and ur name was in alot of those threads

satch

iTrader: (1)

The B/W wire comes from the Main Relay and feeds all of the emission solenoids just inches away from where the BAC is so you could tap into one of those wires as that would be the B/W wire that eventually ends up at the BAC to power it w/voltage w/key to on. The B/W wire at the Air Bypass solenoid to the right of the BAC is the same wire you need.

And pin 2Q is Blue/Green per 88 FSM wiring diagram.

unek87

its a 87 na harness dont know if that makes a difference . thanks brother .im gonna go get some gas and probe those b/w's for key on . it's been 3 yrs since i last drove it . finally got it to start but wont hold idle with out help below a 1000 . i got the tps at 1 volt now but would like to get it to idle out lower so i can readjust that also . hence the bac getting installed . again thanks man

satch

iTrader: (1)

You could also adjust the Variable Resistor to change the idle a bit if need be. And the initial set cnnector needs to be jumpered before adjusting this component.

I believe you also need to make sure you don't cross the wires incorrectly at the BAC for it could damage the unit. So B/W has to go to the proper terminal at the BAC and the same goes for the other wire obviously.

unek87

well i got a stock plug with my bac from my t2 parts car so i just spliced it like this. blue wire to pin 2Q and b/w to b/w with key on in the harness . as for the the initial set cnnector its green with a 2plug right .

and now when i go to start it starts runs for 20 sec and then dies completely on its own with me giving it throttle . and the link i have to the fsm i have is down for the time being :/

satch

iTrader: (1)

Green plug has an Orange wire and a Black wire. And how did the car act before you hooked up the BAC. Differently?

unek87

ok so here is a break down of all the bullshit that is going on . so to start its a 87 s4 6port turbo with s4 na harness , emissions removed,550's all across with all t2 electronics . #1 i have fuel but only when the pump is jumpered at the yellow plug, pressure right now is set at about 38 psi with a fpr an 255 walbro .so i could get it to start but not idle, so i set the tps after a some what warm up cycle to 1volt and then i got it to idle at like 1300-1500 . then found some vac leaks on some of the block off plates so fixed that . power felt stronger then before and vac went up to almost 20hg . but to get that had to give it a lil throttle i mean a lil bit to and it would idle at like 1100 but as soon as you let off it dies . so i figured install the bac that i got and see whats up . well went got some more gas and finished wiring in the bac. started and with me again giving it a lil throttle it runs for bout 20 sec. and kills its self . hope thats

also i forgot that i have a serp pulley setup off a 13b-re from my understanding with fd alt . is the timing marks the same 5 and 20

dennis blackstone

you need some one to draw a diagram for you ,for the bac wiring
pics always works best

unek87

well i feel like i have the wiring for the bac is right . im rewiring my efan right now i had it connected to key on thur that b/w wire in that 6 pin green plug for signal to kick the relay on .so maybe the fan is f=ing with it ? also i dont have power to my pump inless i jump the yellow connector, so i know that maybe a clue

satch

iTrader: (1)

Make sure the AFM door flap is not stuck closed or having problems opening freely and have someone verify that is opens some when you try to start the car and get it running. At the fuel check connector the Brown wire should have voltage w/key to on when there is no jumper present. With the engine running the Brown wire should have close to zero volts.

unek87

door is opening . well after a few hours of going over the car reset timimg at the marks and cas and set tps again to make sure and now im at 1500 on it on power with my efan on which is a good thing i guess so i hook a timing light up and i find the marks more to the left but when i try to adjust i turn the cas counter clockwise and it starts moving the marks closer to the niddle pin but dies out .

i havent adjusted the bac yet . never done a bac adjust before . where on the bac is the adjust screw .. thanks for the help guys.

HAILERS2

Timing has to be done with a hot engine and the rpms under1100 rpm. Above that figure the ECU advances the timing all by itself so what your doing is............pointless..........until the rpms get under 1100 rpm.

BAC has little to no effect when the rpms are as high as yours are. Lower the idle. Make sure your throttle plates are CLOSED at idle. Closed is described in the FSM.

unek87

thanks man i'll check the throttle body out .so new info. come to find out my friend was proping the throttle with a stick before he would get out . so there is no idle . im going to borrow the smoke machine from work tomorrow and see if i have a vac leak cause it will not hold idle .. it kinda bogs a lil to if i give throttle quickly but not so if i slowly bring it up .is the cas from a t2 different then a na ? also im not geting power to the pump with out the jumper in and my gas gauge doesnt work . bad sender ? thanks for the help satch and hailers

HAILERS2

The item that keeps the fuel pump running once the car actually starts up, is.............the afm has a internal switch that makes contact when the vane in the afm moves aft approx 1/8". What this switch does, is send a ground signal to one of the two coils in the circuit opening relay above the steering wheel.

This ground signal is sent from the afm to the circuit opening relay on a BROWN wire of the plug on the afm. Now this BROWN wire is the same wire used when you jumper the fuel pump check connector that you say you have been jumpering to keep the pump working.

Soooooooo I'm not sure why the switch in the afm isn't doing its job since the afm and check connector use the same wire to the circuit opening relay. Both the non turbo and turbo cars have the same circuit in this area.

So this is almost a useless post unless Satch can come up with a reason the fuel pump check connector works but the switch in the afm does not work.

Could be a bad switch inside the afm but frankly I'm VERY doubtful about that.

Usually you can put the key to ON, engine OFF and go to the afm and push its vane aft with your finger and hear the circuit opening relay pull in and the pump to run. You might try that........but you already say the engine won't keep running if the fuel pump check connector isn't jumped anymore. Odd situation.

I've done the non turbo to turbo swap in the past using the non turbo EM harness and this was never a problem in any way.

Maye your buddy can stay in the car and try to keep the rev under 1100 rpm? while you check the timing with a timing light?

Make sure the throttle cable isn't too tight and keeping the throttle plates open.

Also a cold water thermowax with no water going thru it will keep the fast idle cam holding the thorttle plates open a bit. ON a normal car the water temp when up to b/t 120* and 180* will cause the water thermowax to seperate the fast idle cam from the throttle linkage and make the throttle plates come fully closed. Somehow I THINK this might be your high idle problem.

satch

iTrader: (1)

^ One possibility would be the AFM plug/connection is a poor one such that the ground on the Brown wire coming from the AFM is not passing the ground to the relay as it should w/engine running, but when the check connector is jumpered the Brown wire doesn't care that the ground signal is not being sent by the AFM and is glad to take the ground signal from the Black wire in the check connector. So the ground on the Brown is occuring at the halfway point so to speak and not from the mother lode/AFM.

HAILERS2

Actually now that I think of it. you could......key ON, engine OFF. Pull the afms plug off. Jumper the BROWN wire to either of the BLACK wires on that plug. Pump should run proving more than less that the problem lies with the switch inside the AFM.

You'd have to be SURE not to jumper any wires other than either of the black wires to the pure brown wire. NEVER ground the brown/white wire...ever.

unek87

Thanks guys for the help . Well did alot tonight . Found several small to large vac leaks with the smoke machine . So I gotta order a new lim gasket and some injector orings . So because I went that far I went head and pulled the harness also . Any kinda pin out test maybe I should do .

HAILERS2

If you removed the EM harness............ohm out the brown wire at the plug that connects to the AFM to the orange plug called FEM-02 where that brown wire terminates. That wire will be found in the middle of FEM-02. You do this to find out if the signal from the switch intrenal to the afm has a path to FEM-02. This is your problem related to the fuel pump only running if the jumper is kept in the fuel pump check connector.

This FEM-02 is one of two large plugs that go just inside the passengers side foot well and are part of the harness that connects to the engine (EM harness).

Yeah, rock hard fuel injector lower grommets can cause a large vacuum leak and irregular idle.

Theres two orange in color plugs. The jpg attached shows them just inside the large black bulkhead grommet. Which if the two is FEM-02 I can't tell from here. The FEM-02 is the only one with the pure brown wire in its middle socket.

unek87

Ok finished pulling the last few connectors in the passenger floor board and as I'm pullin those orange connectors I see the pressure sensor wasn't hooked up in the kick board . That sounds like a problem maybe ? Im gonna check the harness out right now in the house it's to damn hot out tonight

HAILERS2

The atmospheric pressure sensor inside the series four cars................it can effect the richness of the running of the car to some extent. A lot depends on the altitude of the city you live in. The ECU defaults to sealevel for altitude if the sensor is disconnected so if you live in a sealevel city there will be no effect if it was disconnected. If you live at a much higher altitude the car will run richer than it normally would, if the ATP is disconnected.

Your in Austin Tx so if it was disconnected it will read a little bit richer. Not very noticeable one way or the other.

I'm fairly sure of the default to sealevel if disconnected.

unek87

ok well i got a chance just now to ohm out the brown wire and it ohm's out fine . so does that mean the switch in the afm is possibly bad then like u were saying . what the ill effect of running the jumper in the connector ? im gonna put the harness back in right now and get the uim back on and see whats up with . and by the way what is the brown/white wire ?

satch

iTrader: (1)

With the key to on and the fuel check connector jumpered the pump will turn on and if by chance you are in an accident the pump could still pump away and possibly cause an already bad situation even worse. The probability is slim bit it's something to take into account. This is the negative aspect of a continous jumper in addition to anytime the key is to on the pump will run which might cause the engine to flood. If you're doing diagnostic work on the car and the key has to be on to do so you might unjumper the wires unless of couse you are testing the fuel system.

If you are referring to the Brown/White wire found in the emission harness then that is the Vref signal which supplies close to 5 volts to various sensors in the car (5 of them on an S4) w/key to on.

Also, since the Brown wire ohms out correctly it could mean the connection to the AFM is poor regarding that particular wire in addition to the internal AFM switch being problematic.

unek87

ok well i got it all back together now and it seems stronger then before . it does hold idle now on its on but right around a grand . tps said it was at 1volt at idle . forgot to check at wot . and last night realized that i didnt have the jumper in the fuel check connector and it was running so thats a plus .
so now i finally go to take it for a test drive last night and i got alot of bucking climbing up in the rpm . could my injector wiring be flipped maybe ? also my timing seems to be still off a lil bit . what are people setting there timimg at on 6p turbo setups cause maybe thats it also . i have a 6 rib pulley set up on my car from my part car i had . now when i pulled it off i lined it up just like on the parts motor with only 3 bolts lining up . well i guess it was wrong . so i the other night i pulled my na hub out the attic and compared to the turbo hub . same ****,kool so i start spinning the 6 rib pulley on the hub and got all 4 to line up ,hell yeah . so i look in side the hub and sure enough the key way is pointing to 9'oclock and timing marks are where they should be . . sorry for all the lil info . just wanted to rule out that part of the timing if possible