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Bad ground or bad batt?

17K views 22 replies 6 participants last post by  Erlend 
#1 ·
Heya guys and galls.

Ok so... When my car is running I sometimes feel a slight hesitation. Not at ample throttle, only if I gently push the pedal down. I am also noticing that when the AC kicks in the lights in the cab flicker.

Mods I have that installed that would strain the battery:
3 electronic boost gauges from prosport all wired to the cig lighter for power, acc and ground.
Pioneer 5900 headunit.
Polk db 10" Sub.
Planet Audio 5channel 1000W amp.

The people who did the stereo install added another ground from the neg terminal to the front bellhousing.

I am considering two things, either both or one of the following.
1. Go get some 4gauge speakerwire and gold plated ends. Crimp and solder the ends together and run a ground chain from the passenger strut tower to pass intake manifold to driver intake manifold to neg batt terminal.
2. Go get a high yield battery and replace my stock battery which may not have enough juice to power everything AND the car.

What do you guys think? Are my symptoms indicative of a voltage problem?
Other mods include a full TBE, K&N filter and Cobb Stage 2, but I doubt that those would really strain the battery at all.

Thanks for your help in advance!
 
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#4 ·
yeah 3 gauges... MY BAD ;) 3 boost gauges... come on now... I need those leet gauges to make sure my boost is running right yo... um... yeah. Just 3 prosport gauges.

Have not checked alternator, but it's an 06 with 3k miles... would the alternator really be the culprit?
 
#7 ·
hmmmm... take it too the dealer for them to check the amp and possibly replace it under waranty when I have a new DP... hmm... wonder if they will note the DP and say it caused the problems lawl.

Could I just get out my trusty multimeter and test a few circuits? How much power should I be getting from the alternator and where are a few other good spots where I can test the circuit.

Yeah a 1000W amp does draw a lot of power, which is why I am thinking that I may just want to replace the battery with a higher yield battery and do a DIY engine ground mod. In my book its may be 200$ well spent even if those components are not too blame... because as nagyhead said... just the amp alone draws a lot of current. Add the gauges, the headunit and the sub and your talking a possible drain.. at least that was my thinking.
 
#8 ·
If you had a multimeter why didn't you test the stuff in the first place?Test the battery voltage first.Then start the car and test the charge voltage with all accesories off.Then one by one start turing stuff on (a/c,stereo) and recheck the voltage.Cleaning up the ground points and/or installing a ground wire system will help by creating lower system resistance and bettery continuity.You should see between 14.2-13.6V on the alt.Also try doing a battery load test.Upgrading the battery like an Optima Redtop or Yellowtop wouldn't be a bad idea.
 
#9 ·
I didn't test it because I figured that when everything was wired correctly then the drain would not be too large, and I hadn't considered the alternator. But yeah... I'll go test everything this week.

What is the diff between the red and yellow top?
 
#10 ·
a bad batt will still show 12.6v or higher with a multimeter. Get the batt checked and have the alternator fully fielded, that means, get an amp clamp and clamp it to the alt cable, turn all your accessories on, like stereo w/ sub and amp going, headlights, fog lights, whatever you can turn on. Then rev you engine to about 3k and see what the output is (have someone else look while you rev) if it matches the alternators specs its a good alt. And if its an 06 your grounds should be fine.
 
#15 ·
And if its an 06 your grounds should be fine.
Not always true.They paint the car then attach grounds.You would be amazed at just removing the paint under the star washers can do alone.Also the #1 thing automakers skimp on is the electrical system.You can easily make a ground wire system for cheap by using car audio power wire (8 gauge).Lots of DIY instructions on the Subaru forums of the best places to attach to.Most incompass getting both cylinder heads and the manifold close to the throttlebody.Aluminium is not the greatest conductor and plus you have alot of gaskets and threadlock creating problems as well.Especially if you are running an amp or two.
 
#11 ·
+1 for not being able to check battery with volt meter. Your problem is Amperage... To check Amperage you have to run your Meter "IN Line" to check voltage draw..

Is this hesitation newly noticed? Granted your a 2.5 but your still Turbo and Turbo vehicles tend to have a little more throttle lag vs NA vehicles.. When did you start to notice all this, shortly after the sterio install or has it been some time?

I would check the alt first, it's the only part of the electrical system creating amperage.. If yoy have an AP you can also check your Voltage with it.. If it reads low then your problem is poor grounding "Shouldn't be your problem with a mostly stock 06).. I would start with the Alternator and move onto the sterio system.. The battery is just a storage device, but have them check it while you are there anyway since it's free at Advance Auto Parts.. Upgrading to a Deep Cycle battery is a misconception and will not help with flickering lights caused by AMP drain durring heavy sub hits..
 
#13 ·
That was a lot of awesome info! I have never fielded an alternator before, so I will have to do some searching and find out how that is done.

The hesitation does not feel like turbolag. Let me see if I can explain it. Under low throttle, steady acceleration, I sometimes feel like the car stutters just a tad, simmilar in feeling to what would happen if you ease off the throttle ever so slightly when your just cruising around. Just a slight loss of acceleration. This sensation is not there at half, or more, throttle at all.

The flickering lights only happen when the AC first comes on and the extra part infront of the radiator starts spinning. No flickering with sub hits or anything else.

Why I posted this is simply because the car has a slight hesitation when it is under steady, low throttle acceleration. I would attribute this to something electrical since the 06 has a fully electrical throttle linkage. I may be overreacting, honestly, because I keep reading sooooo many things about hesitation caused by bad grounds, even on newer model rexes, and considering my electrical mods too the car it seemed a logical conclusion.

I'll do what you guys suggest and check the amperage on the alt and then loadtest the battery.
 
#18 ·
If you don't have a grounding issue there is no point to doing a grounding mod.. It's not going to net you anything.. But this discussion is just like breaks and transmissions. Opinionated and no one agrees.. LOL. I had to do a grounding mod becuase with my setup I was only netting 11.4 Volts.. I have to replace all my grounds in my 2002 WRX with better quality and more wires.. My modifications caused the problem..
 
#19 ·
If you don't have a grounding issue there is no point to doing a grounding mod.. It's not going to net you anything..
I went from 13.8V to 14.2V after doing my grounding mod.I'm not looking for nor did i do it for a HP increase.My lights are much brighter and idle is much more stable as well as the alt voltage even with my a/c and stereo going.Less resistance always better no matter what.
 
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