EExA

Well 1 year and a couple months almost 19,000 miles later I think I've pinned down the rough idle in our xA. Right off the bat I put in a pretty heavy audio amplifier (80 amp max draw usually only seeing 15 to 25 amp draw). I've had the car into service before and no one there could figure anything out (more like they didn't really bother to) so hears the breakdown of what I've found and what i've done and whats next.

Car stock, battery stock, ALT stock..
In the summer it would randomly run rough, rough enough I thought it was dying at the light. This was only sometimes for all of about 5 seconds. But the car would be idling fine at about 600 rpm (I have an auto.) then stumble down to about 350/400 rpm for 5 seconds or so, while the car shakes violently, then recover and go back up to 600 rpm and be fine. It might do it a couple times at 1 light and none at the next,. The hotter it is outside the worse it was. I thought 'must be the a/c' well it was kinda. If I turned off the A/c it would stumble like that. Scion says that's correct. I say they're full of it. I've tracked it down to the charging system. Now normally this would happen even with the stereo turned way down, which made me think there is no way it's the battery or draw from the amp.

Added ground wires: this helped a little. for about a day

Added a second 8 gague charging wire to the ALT and power distro block (Even though the amp is direct to the battery (as it always should be, I owned my own shop for 11 years so I'm not a noob when it comes to this)

Added a K&N: doesn't have an effect

Adjusted the idle up 200 rpm, adjusted the pedal and set screw: helped for a day

Added a header; very minimal effect now the stumble isn't so violent i can make a martini but it's still there.

Pulled the stock battery out. Replaced it with a $150 Stinger Dry cell 660 cca 1300 amp output Deep cycle battery: worked great, again for 2 days...

I've narrowed it down to the friggin Alternator. Crappy thing is with the little output of this motor sticking a bigger one on will only put more of a draw on the engine and possibly run rougher. I don't have underdrive pulley's and for the most part the stereo stays turned down. It takes power to make power and it appears that the factory unit is junk. Has anyone tried to fit a Camry or MR2 alternator on this car yet? I'm going to be calling Scion once I meter the voltage output on the alt and battery when it 'stumbles' I'm looking at adding 1 to 5 farrads of caps depending on space. but from the sounds of it the alternator is to blame due to the amount of electrical noise the thing puts out when it first starts. Leave it to my wife to somehow kill the charging system in both of the cars I've got her in the last couple years.

Any chance anyone from Scion R&D/service reads this please feel free to contact me as I might not be the only one seeing this.

Does the scion dealer sell the AEM battery hold down?

Distracted_Thinker

My car was doing that also when i just got it. My dealer fixed it for me. I dont remember what they said it was but Ill ask them and get back to you. But this was after i got a new engine in it.

DaWankler

Are you draining batteries also? I would think if it were an underpowered alternator you'd be draining batteries fairly regularly and waking up to a dead or hard to start car. If it really is an underpowered alternator, perhaps a second deep cycle battery is in order to help alleviate some of the low periods at idle.

I would tend to double check other mechanical problems that might cause this issue also like plugs/wires and maybe the O2 sensor.

Distracted_Thinker

Actually i never drained my battery until i put my stereo system/underglow/ and rear light up sign. But that was just recently. I never swaped my battery still the stock one.

EExA

It's not draining but it is staying at a low charge. The battery I replaced the stocker with could start 4 xA's at the same time. I've had the dealer try the 'low idle' fix which was pointless. I've showed them exactly what is going on with it. The main thing i need to know is if a Camry or somethings stock ALT would fit on the XA bracket. I'm not about to have my alt wound or buy a Stinger one for several hundred dollars when the stocker should be able to keep up with the engine and A/c with the lights on. However something just dawned on me. It happens more the longer your on the brakes. I need to check that I didn;t zing a harness when I mounted the amp. I highly doubt it but the tails+ brake lights are abou 75 to 100 watts which equals out to only a couple of amps. I'm wondering if the stock ALT is just toast.

DaWankler

Of course not, under normal factory designed loads the stock alternator should be sufficient. It's when you add big amps and other electrical goodies that you start exceeding the alternator's ability to replinish the battery.

And that makes sense for an alternator problem. When the engine is idling the alternator isn't spinning as fast so it's not generating as much electricity which will only make it more difficult to keep the charge up.

The fact that you're only keeping a low charge on the battery leads me to believe that is your culprit. As far as wondering if a stock Camry alternator would fit, I don't know about the fitment, but I can pretty much guarantee you that another stock alternator is only going to be insufficient again.

GotXa

scion charging sucks...i have an autometer a/f meter and if i turn on my blinker, the reading will fluctuate from loss of power to the gauge...if i turn on my headlights it just goes all the way to lean

soslowracing

a4

EExA

Your A/f gauge is freaking because the O2 sensor is taking a voltage hit. It supplies somewhere between .1 volts to 5 volts usually. It's seeing a ground pulse or hard drop in the voltage. I'm seriously goung to try to find a contact that I can work with. I've done audio for over 15 years and have never seen a charging system this week. I'll pump the thing up with a bank of caps if needed but I doubt that will be enough. There is just not enough room for 2 batteries and theres no reason this one shouldn't be enough. 500+ rpms should keep a charge but lest not forget it's not like I jst start it and sit there, let alone put it under a hard load all the time, just some of the time.

RoguexA

I'm going Monday to speak to my dealership about the rough idle. We ARE replacing mine. Anyone ever notice how much your RPMs drop when you roll down the windows, turn on the interior dash light, or radio while you are idling?

jct

shocking thing is i have a vacuum gauge in my car (its not a boost gauge)

any thing eletrical robs power from the engine cause my vacuum gauge fluctuates

we already know that the a/c robs the most power anyways

i think we need a slightly more powerful alt.

RoguexA

When I say "replacing mine" i meant the alternator. Sorry I didn't clarify.

PrivateTucker

funny thing, my tC has a weird idle, but only when the rear defroster is on, then the engine drops in RPM's and feels lumpy a bit like a new cam was put in.

RoguexA

Actually it could be your alternator or battery. In our case (aka this thread) it's the alternator. You could do a load test on the alternator and compare it what toyota says the specs should be.

jct

if it is the alternator i think you could swap out the pulley for a slightly smaller pulley too help keep up with the output maybe

xAwahl

let me know what happens with it ...mine is doing it also, and would like to know how to fix it...i just thought my system was too big for it...but after addin a cap it didnt help...keep us posted

RoguexA

No the alternator just sucks. You need a new one. It does not generate enough power. My husband and I did a load test on the alternator in my xA. It failed.....BAD.

jct

post the results pls if you could

RoguexA

Sowwy......I traded in the blue angel last friday for a 2005 Nissan Frontier. I always wanted a truck. I was just so dang tired of all the crap going on with my xA. It was rediculous. For the money I was paying, I could have a much more reliable vehicle. Did I mention my dealership broke my intake when they installed it, covered it, and I barely discovered it last week? Ya....11 months of sucking in unfiltered air..........AHHHHHHH. Anyway, I obviously don't have the alternator problem anymore. Good luck to you all!

Emfdiablo

lol, if someone fixes this let the world know please, ive only made the problem a lil better with ground wires, a voltage stabilizer, and a lighter crank pulley (not underdriven)
as for the frontier, my first car, which my lil bro now has was a 2001 nissan frontier with the v6. bad ___ car, i put that thing through so much and it never ever failed me. I had it running faster then the supercharger ones lol. Fun fun, ill never forget my first car.