Unseen24-7

Okay here's my main problem. When I start the car cold the neo (all my voltage readings are from the neo) says 14.4v, this goes down gradually as the car warms up. If i started the car and just let it run until it settled to idle the voltage would go from 14.4v to 13.9v-14.0v. Not a big deal right? Once I start driving it the voltage settles between 13.8 and 13.9. This is with NO accessories on, no a/c (it's actually not even hooked up), no stereo, no headlights, nothing.

This is where it gets bad, once the car has been driven for a while and the efan has been running, if i come up to a stop sign and hit the brakes my voltage drops as low as 12.9v and the car stars idling rough. If I have any accessories on it can go even lower. I thought these FD 100amp alternators were like crazy powerful and mine can't seem to handle brake lights, efan and running the car all at the same time. Anybody have a good idea of what is going on.

Oh I should mention that it runs really hot, like i'm about 85% sure i have a blown or starting-to-be-blow coolant seal, which is the likely cause. This makes the underhood temps really hot, so i'm wondering if this could significantly affect the efficiency of my alt.

The engine...
stock s4 na with 6port sleeves, rods and actuators removed.
t2 exhaust mani with the stock s4 turbo spaced off of the manifold.
t2 i/c front mounted (backing plate removed)
2.5" dp to 2.25" midpipe to stock catback.

Electrical...
FD alternator
Apex'i AFC neo
PLX wideband
autometer boost gauge
fiero electric fan

Thanks in advance

KhanArtisT

iTrader: (2)

When you experience the voltage drop at idle with the accessories on does the idle drop down really low? Could be something as simple as a faulty BAC (which should readjust idle after detecting loads or accessories) or vacuum leak, its easy to do a resistance check on it if you have a DMM.

And I would make sure the entire cooling system is up to par before you blame the coolant seals about the heating problem. FSM>troubleshooting section.

st1llet0

iTrader: (2)

I'm a bit simple minded, but could it possibly be a poor battery connection?

Aaron Cake

iTrader: (1)

Check the simple stuff like the battery connections and main power feed from the alternator to the fuse box.

Does your idle speed stay constant?

Though it does sound like there is an issue with the alternator. As it heats up, the regulator may be failing.

jackhild59

iTrader: (7)

What is your normal idle speed (when its not hot, efan and brakelights running at once)?
What is the idle dropping to when it idles rough?
Is your BAC working properly, because if it's not, the car will struggle to idle, especially at first as the rpms drop under a load from the alt. I don't think that the engine is idling rough at 12.9 volts due to low voltage.

How does the starting-to-be-blow coolant seal affect the temperature that the car is running?
Are you consuming coolant?
Is the coolant level low?

How are you controlling the temps in your cooling system (temperature controller?) What temp is it set at, on/off?

Do you have an actual after market gauge that is telling you what the actual coolant temp is?

Is the car really running hot and overheating or is this your concern based on how hot it feels under the hood?

You need to dial in the specifics before we can help you. That alternator may be just fine, but you won't make 14.1 volts if your idle is dropping down too low. This will cause the roughness as the engine struggles to run.

Unseen24-7

I will definately look into the various electrical connections under the hood (battery, alt, etc). I didn't at first even consider the BAC to be faulty so i will look into that as well.

I have my idle set at about 850rpm(once the stupid accelerated warm up finishes). This is as high as i can get it, I have the variable resistor cranked (it was nearly cranked when i first adjusted it), and the screw on top of the tb is pretty much maxed too. And they are definately turned in the right direction, i made sure that i was increasing the idle and not decreasing it.

Here's the startup sequence...

start car...revs to 3k...put in clutch and put in 1st...idle drops to 1700...slowly goes down to 950 and stops (assuming i haven't driven the car yet). Lately when the car has been sitting for a day or 2 it stalls outright once i press the clutch and put it in 1st, but this could be an unrelated issue too.

It idles consistantly, once warm, at about 850...if i'm slowing down to a stop sign it can drop as low as 550.

No I don't have an aftermarket temp gauge (i know i need to get one) so im going by the stock guess-o-meter. That being said i've been told that normal operating temp for an s4 na is about 1/4 on the gauge. Mine settles in at about 1/3 to 1/2 depending whether it is a cool night or a hot day. While regular driving it consistantly sits at 1/2 (more if im boosting).

The underhood temps are not obscenely hot, but i also haven't made a heat shield for the turbo yet...

Now before you try to tell me that it's my efan/shrouding/etc, i will say that it did the exact same thing when i still had my stock clutch fan.

It does consume (or leak, i guess) coolant, though not as much lately.

jackhild59

iTrader: (7)

When it drops to 550 rpm, it will shudder because its about to die. the volts may also drop for the same reason.

Keep in mind that if your engine speed is dropping to at the same time you have a pretty good electrical load and the bac is not working right, you would expect exactly what you are describing.

I really think you have an idle problem and maybe you need a new thermostat.

Unseen24-7

Well i've gathered that i have an idle problem, now the question is how do i fix it?

Replace the BAC?
Fix/Rebuild the BAC(if that's possible)?

I've been meaning to replace the t-stat and buy a fluidyne rad for a while now. Guess i should get on that...

88rxn/a

iTrader: (6)

VAC/boost leak....
low idle = low voltage...
belts not turning the alt fast enough?

Unseen24-7

Well turns out it I had a huge hole in my TID, so I built a slightly modified TID which seems to have cured my poor idle, but the low voltage thing still remains...