this always happens... bad alternator???

[bk12321 10+ year member]

my old car did this exact same thing before i sold it about a year ago

i installed my new system about 3 weeks ago, and now my car idles fine but when i put it in drive SOMETIMES the rpms start going up and down every second or so, from around 200-400 up to about 1600 jumping up and back down over and over again.... basically the same thing happened to my last car. also when ur going faster its fine but when u are slowing down once u stop the car will shut off or idle very low for a second and jump back up.

bad alternator??? and i thought running it at 4 ohms would prevent this from happening again but apparently not. system in sig

doesnt always do it

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[bk12321 10+ year member]

anyone???

 

[PESteele 10+ year member]

sounds like your car just sucks

is it the rpms that mess up or voltage?

 

[bk12321 10+ year member]

sounds like your car just sucksis it the rpms that mess up or voltage?

the rpms mess up i have no clue about the voltage

but my other car did it too with a completely different system........ what could be the problem????

 

[bk12321 10+ year member]

still lookin for help...

ive never heard of this happening with anyone I know and its happened to me twice now.

 

[mlstrass 5,000+ posts]

My "guess" would be that your voltage is dropping too low for the battery to properly power your car's electrical: computer, fuel pump, etc... If your system is really what's causing the problem.

Otherwise get it into a shop and put on a diagnostics machine: could be IAC, injectors, vacuum leak, lots of things that can make your idle surge.

 

[mlstrass 5,000+ posts]

If you have a DMM test your battery voltage with the car off and then with it running and rev it up to 2500+ RPM to see if the voltage increases to make sure your alternator is working.

Battery should be around 12.2 with car off, not sure what your alternator does voltage wise, 13.6 - 14.4 is what most cars do.

 

[coolahan 10+ year member]

vacuum lines

 

[helotaxi 5,000+ posts]

Sounds like an engine management problem vice an alt/electrical prob. Vacuum leak, fuel filter, plugs etc... Take it to a good mechanic. My old truk would do something similar and it was eating O2 sensors.

 

[bk12321 10+ year member]

it just started doing it when i got the system and my old car did it about a month after i got that system too, so i dont think this is just a coincidence

i really need to invest in a dmm ****it

 

[bk12321 10+ year member]

by the way thanks to everyone for the input so far, im looking at everything dont worry //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Ctminime 10+ year member]

i had the same problem with my old grand prix... in my case my alternator was working but not putting out enough to power my tx1505d and my fuel pump haha that was the problem.... but what is causing ures could be completly diff so have it checked out

 

[bk12321 10+ year member]

i had the same problem with my old grand prix... in my case my alternator was working but not putting out enough to power my tx1505d and my fuel pump haha that was the problem.... but what is causing ures could be completly diff so have it checked out

so wait what was the problem??????

the fuel pump was bad and ur alternator wasnt powerful enough??? sry it was a little confusing to me lol

 

[Ctminime 10+ year member]

no my alt wasnt powerful enough to power my system.... fuel pump didnt get enough juice and therefore malfuctioned

 

[bk12321 10+ year member]

no my alt wasnt powerful enough to power my system.... fuel pump didnt get enough juice and therefore malfuctioned

so you just had to get a new alternator? or how did u fix the problem

because of how my car is acting its leading me to believe its the fuel pump