so ive narrowed down my problem

i hit a wall at 3.8k, wideband goes lean, wont go past it. whole nine yards.
dont say its grounds, its not the 3.8 stumble, its all out fuel cut when the secondaries are supposed to come on.

so im pretty sure my secondaries arent firing. i ran new power to them, but still nothing. ive tried both my 720s and my 550s, neither work. had a fucked up clip on the front rotor, replaced it, still doing it. i ran new power to both secondaries, still doing it.

im this close from running new wires to the ecu from the secondaries, just to be sure.

what are the possible causes of the secondaries not coming on at all?

 

bad secondaries? stuck closed?.... there are other possibilites beside it being a wiring/electrical problem

 

This is a non turbo car??? A n/a????

Anyway, power should be at the black/Yellow wire at each injector anytime the key is to ON.

What makes the injector work, is a ground being pulsed by the ECU to the other wire on the injector (so to speak).

It only does that normally if the engine is under LOAD and the rpms are above 3800 rpm. You can duplicate LOAD in the driveway by pulling the vacuum hose off the pressure sensor and plugging that vacuum line. Now each time the engine is rev'd above 3800rpm, the secondarys will come online and pulse.

So you might ohm out the secondary injector wires from the injector to the ECU's small plug. But I see no way on god's green earth they'd be *open* unless someone cut them.

 

Have you confirmed that there's +12v at the power side of the secondaries?

There are only a few things required for the secondaries to come on.

1. The injectors have to be able to fire. It's possible that both sets of your injectors are gummed up to the "not able to fire" condition - I spent a while trying to get a particular '7 started, and just couldn't get the damn thing to get gas. Turns out all 4 injectors were gummed up. Put in 4 known-working ones, it (more or less) fired right up. You can test your injectors by applying voltage and making sure they click. You'll want to double check the proper test procedure, some injectors need resistor packs to prevent them from burning out.

2. Power to the injector. There should be a constant +12v to one side of the injector. This is pretty easy to test - use a voltmeter.

3. Connection to the ECU. This is a bit tougher to test, but with some wire extensions, you can test continuity fairly easily. Make sure power can get from the ground side of the injector to the ECU.

4. ECU drawing down the signal line to fire the injector. This may be where your problem is - the driver transistors in the ECU do occasionally go bad, and the ECU is unable to fire the secondary injectors. This can be fixed by replacing the transistors, or just replacing the entire ECU.

-=Russ=-

 

If a shop installed a stereo...

I agree, the connections to the ECU aren't likely to be the issue. But it's worth confirming them.

-=Russ=-

 

Well your right. You don't have to ohm the wires out from the injectors to the ECU. Just install the elect plugs on the injectors and turn the key to ON.

Then pull the small plug off the ECU and make sure there is 12vdc on each of the injector wires in that small plug. That ocnfirms the wiring to the ECU is good.

 

all 4 injectors are good, they all click when i give them seperate power and ground.

the injectors have power at the black/yellow wire, i know this because i ran it myself to be sure of it.

this is on a s4 NA block gone boosted with tii everything, using the NA harness just like your post hailers.

im starting to think this ecu is junk, as this harness never had any problems at all before. if i tear it open will i see some burnt up transistors?

ill check for power at the ecu pins when i get off work

 

What's the number on the ECU???? N332 or N333?????

What are the chances you have the injector plugs on the wrong injector???? Disregard this question if the car idles pretty much ok.

If this is a N340 ECU, I think there is a thread on those being *different* in some ways. Pay no attention to this if your ECU is a N332 or N333.

 

n332 i believe, ill check. it was from a 88 tii

the injector plugs are on right, theres a short one and a long one, they can only go one way pretty much.

idles fine, drives fine, boost fine, just when the secondaries should kick in at 4kish it just hits a wall, stumbles like a fuel cut, wideband goes lean.

 

its a n333

 

check fuel pump... mine did the same thing but would lean out under any load

 

k, wires to the ecu are good, they have 12v going through the injectors to the ecu.

so, injectors have power, injetors have ground to the ecu, they click then given seperate power and ground.

so short of my ecu being friggen shot, is there anything else that would cause the ecu to not fire the secondaries?

 

runs 9.xx AFR under boost to 4kish when the secondaries should stage on, then fuel cut lean hit a wall.

so how can i see if my ecu is shot?

 

i have a rtek 1.7 for sell??? 130 shipped and 100 for 2 very low miles 720s low imp.

 

i also have a n332 stock for 75

 

Electric or mechanical OMP?

When the electric OMP starts to bug, the car will cut all power above 3500 rpm. It happenned to my cousin and I witnessed it first hand. We changed the OMP and everything was fine and dandy afterwards. You can check it with a voltometer.

 

s4.
no omp.
blocked off

 

adjusted the tps, redid the timing.

now it cuts out at ariound 5k and 8psi.

is there anyway to check my FCD with my multimeter to make sure it works?

 

Ive done that using a meter. Put the meter up the backside of the BROWN/RED wire in the boost sensor OR at the ECU pin 2B.

Then, with the key to ON, apply pressure at the nipple on the boost sensor. As you apply pressure, the voltage on the meter will rise and finaly stop rising at approx ....................ah shucks, I forget. I think about 3.65 vdc. The voltage will stop even though the pressure is still rising.

I used a MITTYVAC. It does pressure and vac.

Or go for a ride and have the meter up the back of the pin 2B and have someone look at it as you boost the car. The voltage should clamp around 3.65vdc.

I'll do some looking, but I think 3.65 is a fairly representative figure.

I wouildn't apply more than around 10psi at the boost sensor. Actually a MITTYVAC won't do much more than that anyway.

FCD

 

i have the SAFC's throttle input hooked to the boost sensor.

ill go into sensor check and see what its reading when it cuts.

if its reading to high, is there any way to fix it? add a resistor or something? i have an event tomorrow and i realllllly want to make it.

will the ecu freak out if unplug the sensor and add in a bunch of fuel to compensate?

 

its not boost cut, unplugged the boost sensor and theres the cut, right smack dab at 3800. i read it forces the secondaries on at that rpm when the sensor isnt there or is capped off.

so, my injectors definitely arent coming on.

so unless some other sensor or something can make them not come on, its the ecu?

events cancelled, so i guess i get to have time to figure this out

 

okay what the ****

tried my NA ecu for ***** and giggles

same

damn

thing.

cuts out like a fuel cut, wideband goes lean.

so, injectors are good, wiring is good, ecu is good. WTF.

what in the world could possibly cause my injectors to just not come on? afm? some other sensor? waht else has control over the secondaries coming on?

if it was an ignition problem, like bad plugs or misfiring or soemthing, the wideband wouldnt show lean would it?

only thing i know is wrong is that the O2 sensor is not wired up, but the ecu only uses that for cruising, and its not throwing a code for it anyways. the AIT sensor is only for helping with hot starts, correct? mine might be in a bad location. but neither of these should make the secondaries not come on.

 

How does the engine run at lower speeds? How does it run at idle?

IF you drive the car on the hwy, and drive slooooowly over the 3800 rpms and drive say up to 4500 in a gentle manner, what happens???????? I'm talking with all vacuum hose/electrical plugs on the engine. Use the N333 ecu.

You have a SAFC don't you. At idle with a hot engine, can you look at the VOLTAGE output of the boost sensor? And write back what it is. Maybe also the afm voltage. NOT the percent but the voltage.

 

You said "Don't say it's the grounds" - are you SURE? The ECU ground to the engine under the intake manifold is pretty critical. If it's bad, it's possible that the ECU can sink enough current to ground to fire the primary injectors, but when it tries to bring the secondary injectors online, the increased current flow is too much for the ground, the ground voltage raises up, and either the ECU can't flow enough current to fire the injectors, or the ECU is no longer getting enough voltage to run.

You could test this by probing the voltage difference between the grounds at the ECU and the bare frame, and then revving the engine. The difference in voltage between the ECU ground and the frame should be basically 0 - a few mV is OK, but if you start getting readings in the >1v range, especially as you try to pass 3800 RPM, it would indicate bad grounds.

More importantly, a bad ground to the engine block would explain why everything looked just fine, but two different ECUs had the same issue - it's a failure that would equally affect both ECUs.

-=Russ=-

 

runs great at idle, runs great up until 4-4.5kish, boosting and all, pulls nice, wideband reads 9-10afr. 8psi by 4-4.5k