drewl

S4 motor, S5 turbo, cone filter on stock TID, RB turboback exhaust. recently fixed exhaust leak from turbo to downpipe (i think).

i've read up on all of my symptoms and found many possible culprits. i'd like to think that some of them are related to eachother and i could solve them in groups.

ok here we go:

1) 3800 rpm stumble.
2) starter doesn't engage every time. i can hear the relay clicking though. battery is brand new.

sometimes the relay clicks quieter than normal, and the e-fan is not running. then suddenly they will both come back to normal and the car will start.

sounds like bad grounds, or maybe just one bad ground?

3) METER fuse likes to blow. for a temporary fix, i got a circuit breaker. it will trip a few seconds after i start the car, then the car will idle better for a few seconds until the circuit is closed again. then it'll trip again a few seconds after that and idle better until it closes again. it trips and recloses twice, and the engine idles better while that circuit is open. the circuit breaker does not trip until the next time i start the car.

4) won't hold idle when it's cold. i have to turn my safc to +20% @ 1000 rpm on (LO) to idle at ~800. after it's warm, i don't need the safc anymore. it does, however, idle kinda rough.

it used to do the cycling thing between 1000 and 1500 rpm when it was kinda warm, and hold steady idle at 1500rpm when it was fully warm. for some reason it stopped doing that. now, if i hold the gas pedal down, 1500 is still very steady, unlike the rough 800rpm.

so what's wrong with my engine? bad ground, exhaust leaks? vacuum leaks?
thanks in advance.

EDIT: here's my AFR graph, if anyone wants to see

WAYNE88N/A

Which relay are you talking about clicking during start? The starter solenoid? The circuit opening relay?

I'm sure you've done a good visual of all of the major wiring terminations, battery terminals, etc by now, right?

Could be a bad ground somewhere, but that wouldn't be causing the fuse to blow...You add anything to the METER circuit, or is it still stock?

If it's only blowing a couple of seconds AFTER start, there seems to be nothing on the schematics that would cause that to happen in the exact time frame you mention. Some stretching would include the alternator warning light circuit (and CPU and/or buzzer), or maybe the warning lights panel. Who knows? Try to isolate as many circuits/ components as you can (unplug things) to narrow down the list of possibilities. The back-up lights switch and wiring is also on that circuit, keep this in mind...

Other than a vac leak that gets worse/ better as she warms up, I have no idea...An leaking EGR valve block-off plate caused some weird **** on my car a while back, so variable vac leaks can cause havoc on a normally running engine...

WAYNE88N/A

Also, if you have the technical ability to do it, I would be reading out all of the sensors and inputs/ outputs at the ECU while she's idling hot and comparing them to FSM specs. Might provide a clue as to what's going on...

ilike2eatricers

#4 Any cracks in your TID? Checked the TPS? TB mod done?

drewl

starter solenoid is what i hear.

i looked for loose/damaged wires, and i found one COMPLETELY MISSING one from the rear iron to the chassis. added one and nothing changed. it does look like someone was playing with wires near the starter though. i'll have to unravel the harness and take a look when i get a chance.

i have added nothing to the METER circuit, it's all stock. i'll try taking things out of the circuit and see what happens. so gauge cluster, idiot lights, climate controls, and reverse lights are all what's on it?

i'll see about checking all sensor voltages.

my TID has no cracks as far as i can tell. it's not hard like most. it's still pretty flexible. it might have been replaced not long before i got the car.

TPS is 0V at off throttle and hits 5V at 1/3 throttle.

TB is stock.

thanks

Kory_yahi

Make sure your gas hoses are hooked ok. My car was bogging down at 3,800 because there was air in the hoses or a slight pinch or something.

drewl

well, it turns out it was my reverse lights blowing the METER fuse. only time i go in reverse is when i first start the car....that's why it doesn't keep happening until the next time drive
now just have to fix it.

drewl

forgot to mention
when the METER circuit is open, the power steering is either gone or working at a reduced level. what's up with that?

drewl

so after i was convinced being in reverse was tripping the circuit breaker, the behavior changed. now it trips no matter what, even when the car is off. it trips, then resets and trips again right away.

the car will only start when the breaker is tripped. the engine runs fine when it's tripped. when it resets, the engine stumbles like the 3800rpm problem. it's so annoying that i just had to take the breaker out until i find the problem.

WAYNE88N/A

Back to square one, eh...

Sure it's not one of the wires going TO the reverse switch that's chaffing against the tranny and/or chassis?

drewl

i'm gonna have to check it out.

the fsm isn't helping me much with this. can anyone describe/show where all the wiring and components of the METER circuit are?

drewl

i went and got my own multimeter cuz my friend is gay and doesn't wanna help.

SO

what do i set it to and where do i test...
i'm such a noob for electrical stuff.

drewl

noticed today that with the circuit breaker, the car will idle without the help of safc, even when it's cold.

drewl

went around testing stuff today. with one lead on the circuit breaker and the other lead on a known good chassis ground, i got 11.4V when the circuit is blown and 7.5V when it's good,

so 3.9V are going to a short somehwere?

WAYNE88N/A

Wha? I gotta assume you're not putting the meter leads in the right spot, because if you are you've got some really funky stuff going on.

On the LOAD side of the breaker (not power side), you should get system voltage with the breaker set and 0 volts with it triggered (popped). If you're getting any voltage with the breaker popped, then you have another power circuit that somehow got spliced into the meter circuit- which may or may not explain your problems.

If you have a direct short somewhere, using a meter is not always the best way to find it. You need to get the schematics, divide the circuit in half by disconnecting a plug or component, reinsert a fuse, and see if it blows again. If it does, the first half of the circuit is bad. If it doesn't, that last half is bad. Continue dividing the bad part of the circuit until you've nailed the component/wire section.

Or, disconnect everything in the circuit you can, then reconnect one plug/component at a time, working your way down the circuit towards the grounds, until the fuse (or circuit breaker) blows...

I'd start looking for funky wiring jobs first

drewl

divide the bad part of the circuit... of course.
with a BS in computer science, you woulda thought i could think of that, huh? that's the same way you search for things in a sorted list.

well i gotta go to work now. i'll do more later.
thanks for the help

drewl

called in to work so i can continue to do this...

ok, so i tested the circuit breaker again, this time on the other side of it. i got 7.5V when it's good, and 0V when it's tripped. makes sense to me to get 7.5V.

next, i unplugged the gauge cluster, idiot lights, climate control, and reverse lights. breaker still tripped with all of those unplugged, and gives the same 7.5V when not tripped. is there something else on that circuit i don't know about? or... this means the problem is somehwere between things

WAYNE88N/A

Why does 7.5v make sense? Is the battery damn near dead?

It sounds like your problem is way up the circuit, before the breaker. My guess...

FWIW, on an S4, the meter fuse feeds:

auto tranny control unit
alternator warning light relay/CPU/alt excitation circuit (look into this!)
ABS control unit
gauge cluster
back-up lights
warning lights panel
CPU/ buzzer
AAS control unit
theft deterrent control unit

drewl

of course 7.5V is not what it should be, but makes sense given that i'm hearing the fan operating at a slow speed. i would expect the voltage to be low.
is that fan even supposed to be on with the key at ACC?

anyways, wow, all those things are on it. the fsm is beginning to make a little more sense now.

now i got something to keep me busy for a while

WAYNE88N/A

A fan shouldn't drop battery voltage to 7.5v, unless the battery is weak. 10 volts maybe minimum...

Just for $hits and grins, pull the 2-pin plug off of the back of the alt, and see if anything changes. That circuit popped in my head as I was listing the components for you...

Note: DO NOT start the car with that plug disconnected

drewl

had to pull off the intercooler to take the plug off the alternator. with the intercooler off, i saw a wire with connector dangling, and a sensor in the intake just before the TB. intake temp sensor? i went ahead and plugged it back in.

then i unplugged the alternator plug, and the harness was wrapped in yellow electrical tape, which tells me right away the previous owner was screwing around with wiring. pulled the plug and.... no difference. left the key on ACC and followed the yellow harness. then i heard what sounded like arcing coming from around all those solenoids and vac lines. didn't see where exactly and didn't hear it again. followed the yellow harness some more and found 2 yellow/red wires coming out of it and going no where. looked in the FSM and i guess one's to the oil pressure sensor and the other is to the condensor. one had a plug in the middle, followed by more wire. it was burned and melted. the other one ended in a plug, so i'm guessing that's the oil pressure one. it was in good shape. i don't need the oil pressure sender wire since i have an aftermarket sender/gauge now.


i'm not saying the fan is using all that power, just that the fan is the most obvious sign that the METER circuit being closed is draining the power somewhere else, so the fan (and everything else in the car) gets only 7.5V. it goes full speed when the breaker is tripped.

that does make sense... right?