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Discussion Starter #1
hi all ,

recently, i changed all my crank sensor, plugs, engine oil, fuel fiter, and air fiters. as i discover the car was good and smooth for the first day. but on the second day i was driving and notice the RPM were going up and down from 400-900 RPM sometime i thought it would die on me again, but if applied some gas it was good to go. so instead, i park aside and shift it to drive gear and hit the window buttons upward and hold on to two or more button for few second to see if the idle is moving ..wow, by holding the window buttons upward and hold on to it for few second or more my RPM jump from 400-900 so this mean that all my tune-up is good but my battery juice is too low that is why the RPM shift up and down?? or should i change my battery not my drive belt...yes, mine is 1999 9-5 auto at 67k miles. thx
 

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So your weak battery is causing undue load on the alternator, which drags down the idle and then the ECU sets in and flicks the throttle a little to bring up the idle and the whole things repeats to give you a bouncing effect. It seems so simple now. :p
 

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Discussion Starter #3
rpm

i hope that would be the cause so that way i can just recharge the battery or buys a new one to replace it but how i do i test if the battery still good and normally how long should a battery last in term of life span??
 

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4-6 years is considered normal, and there are outliers in each direction. Take the car to just about any mechanic and they should be able to do a load test on it. If you have a battery charger handy you can do a psuedo test where you start the car repeatedly. If the battery can't start the car after a couple starts your battery is either low on charge or on it's way out. Not exactly scientific, but it'll give you some idea I suppose. If your battery is more than 6 years old I wouldn't bother and just put a new battery in it, you'll need one soon enough if it isn't the actually problem.
 

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Discussion Starter #5
rpm

ok thx i have no idea how long the battery was there for since i got it 2 years ago..so i suppose its old enough now to replace..thx
 

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rpm

ok after recharged my battery the mechanic told me i do not needed to buy a new one since most car like 9-5 uses to much component so the battery will be recharge by the alternator and it also does make the RPM noisy if u hit the window button upward and hold for one or more seconds. anyhow, i realized after recharging the battery the car still feel like hesitation making the RPM feel like it would die out..speacially when its a rainy day..anyhow, learning from other posting i am starting to belief the DI is another factor into my RPM hestation since i have changed everything except the fuel pump..anyhow, i am also thinking it could be my drive belt or a/c belt since it really shift a bit when the engine runs on drive gear.. ok i will let u know if they are cause by the DI and I would not wanted to think about the THrottle since that is too much $$ to spend. thx
 
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