Well i been having idle problems, but i went to go start her up. And as usual i primer her up before i start her, and she usally dies on the first try, then on the second she adjust herself and she idles (Idles low but idles). SO i press the brakes and the light dims as usual but i kept pumping hte brakes and the car shut off on me. But once the car is on isnt the battery not working anymore and the alternator is charging the cars battery and instruments.

is my alternator bad, and can i test it by starting the car and removing the negative cable. If she stays on then alt is good if not then alt is bad. Can this damage my computer

Jason NYC

 

Sounds like a vaccuum leak, a big one. You can test the alternator that way and don't worry it won't hurt anything. The batteries only there to start the car.

Brent

 

yes, it can... the alt can spike 16+ volts doing that, so it wouldn't just be your computer but everything electrical in the car.

 

that would be radically wrong. Batteries are used not only to start the car, but to provide referenace voltage on S5 and S6 alternators, as well as capacitance for the 12 volt+ whole circuit, and to provide reserve voltage in high demand situations.

There are some alts that will spike so high they burn themselves out (as well as most of the electronics in the car that are on at the time) if the battery is disconnected while the car is running.

 

NOt to sound retarded but i truly dont know that many vacuum lines only a few can u guys have real pics identifying the vac lines on a s4 gxl. Im sorry, i just suck with vac lines

Jason NYC

 

spray some starting fluid around the intake lines and runners while the engine is running. A leak will show up as an increase in RPM, when the starting fluid is sucked in

 

So i willl have to remove my K&N intake and spray the fluid inside the flap where the air gets sucked into my car. I gotta go buy some starting fluid

Jason NYC

 

NO!!!!!

Don't take anything apart.

Spray the top of the motor where the vac lines and intake runners are.

Avoid spraying into the air cleaner and onto the exhaust manifold

 

Sorry, still learning how to work on these puppies. I do the work 98% on my own so i try to do as much research as possible (time permitting) or looking at the haynes FSM while in the can lol.

Got pics of the Vac lines, are they the hard rubber black ones all over the top of the car lol

Jason NYC

 

I had a similar problem, turned out to be a stuffed alternator.
Wasn't charging enough, so when i pressed the brake or put any load on the electrical system the car would die.
Got a new alternator and sorted everything, no problems since!

 

i might just get a mazda alt, but not quite yet im low on funds but ill def look at the vac lines. Can someone identify em. Or got links to sites with actual pics.

jason NYC

 

what is the voltage when you foot is on the brake??

should be above 13.5 at idle

 

Thats the funny part the idle (Even when its low ) its at 13.5, when im hitting the gas its at 14, and just idling back to 13.5.

Wheni crank the car its at 12 or so. But car always starts

Jason NYC

 

Well, a new alt should be putting out 14.4 at idle, even with your foot on the brake.

Doesn't sound like you got a new alt, or even a remanufactured one, but rather a rebuilt one, where only the broken parts were replaced.

But regardless, anything above 9 volts and the car shouldn't die

 

When i hold the brakes the light dims but stays. When i continously pump the brakes the idles starts going down and down then dies. Once the car nice and warm this doesnt happen

JasonNYC

 

which points to a vac leak and that the cold start assist it not connected or working properlly

 

could the cold start assist not be working cuase the car was auto and now i converted it to stick?

Thanks for ure time Icemark

Jason NYC

 

All good points, however he's got an 87'. Not an s5 or an s6. I realize it's also used in high demand situations. If your worried about a spike turn the lights and heater fan on. Oh yeah, I totally agree with the other guys, do not ever use starting fluid and don't spray carb cleaner in the afm. Both of these will likely cause damage and the starting fluid has resulted in many blown engines.

Brent

 

so that if teh alt spikes you blow out the lights and heater motor???

Common man, this is not some 60's chevy. One of the worst things you can do is disconnect the battery when the engin is running on a modern car.

Ah, yeah... name even two people that have blown a rotary motor by spraying starting fluid into a motor. I can hear it now," my buddy knows this guy who, knows this guy that did that once..."

I think you meant you disagree not agree.

Anyway starting fluid sprayed around the intake runners and vac lines while the engine is running is a perfectly safe method of checking for vac leaks. As mentioned in other posts the RPM will raise slightly as the starting fluid is sucked in through a vac leak.