Low voltage, bad tps? help me out
11-21-12, 05:00 PM
#1
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Thread Starter
Low voltage, bad tps? help me out
hey i have a 89 gtus... I've been having a issue. first off i bought a brand new battery today and also replaced the alternator, checked the coils and plugs.. everything is good but for some reason my cars voltage still drops. the car had a s4 alternator so the wires were cut. i reconnected them using butt crimps to make sure they were good but now i have no idea whats going on..
also my car has been idling rough and backfires alot during idle thus causing a thumping sound as if someones kicking the trans. its not consistan it happens on and off. i have been told it could be the TPS causing the rough idle and the backfiring is causing the motoro and trans to shake alot because of my bad mounts.
my logis is that the cars backfiring because of the the low voltage causing poor fuel delivery wven with the new pump which causes the car to shake and make that noise because of my bad motor and trans mounts... anyways idk some one help me out pleae
also my car has been idling rough and backfires alot during idle thus causing a thumping sound as if someones kicking the trans. its not consistan it happens on and off. i have been told it could be the TPS causing the rough idle and the backfiring is causing the motoro and trans to shake alot because of my bad mounts.
my logis is that the cars backfiring because of the the low voltage causing poor fuel delivery wven with the new pump which causes the car to shake and make that noise because of my bad motor and trans mounts... anyways idk some one help me out pleae
11-21-12, 05:28 PM
#2
Never heard of an S4 alternator in an S5, but are you sure it is wired correctly as an S4 will be wired differently than an S5? There is a diagram of how this alternator is to be wired up in the FAQ section/thread (shows the difference between S5 and S4). If you were to take the voltage reading of the alternator's output wire what is it while idling?
The TPS is to be set w/the car fully warmed up (not partially or close to, but completely warmed up). There is a Green/Red wire at the TPS plug and it should read 1 volt w/key to on and again, the engine as warm as it can get.
The TPS is to be set w/the car fully warmed up (not partially or close to, but completely warmed up). There is a Green/Red wire at the TPS plug and it should read 1 volt w/key to on and again, the engine as warm as it can get.
11-21-12, 11:42 PM
#3
Stuck On 7
Thread Starter
Never heard of an S4 alternator in an S5, but are you sure it is wired correctly as an S4 will be wired differently than an S5? There is a diagram of how this alternator is to be wired up in the FAQ section/thread (shows the difference between S5 and S4). If you were to take the voltage reading of the alternator's output wire what is it while idling?
The TPS is to be set w/the car fully warmed up (not partially or close to, but completely warmed up). There is a Green/Red wire at the TPS plug and it should read 1 volt w/key to on and again, the engine as warm as it can get.
The TPS is to be set w/the car fully warmed up (not partially or close to, but completely warmed up). There is a Green/Red wire at the TPS plug and it should read 1 volt w/key to on and again, the engine as warm as it can get.
11-23-12, 11:44 AM
#4
Stuck On 7
Thread Starter
update: i was right about the thumping sound it was the mounts so im gonna be ordering banzai poly motor and trans mounts still cant figure ot why the voltage is dropping the way it is so im going to run a wire from the battery to the alternator for now till i can figure it out.
11-23-12, 01:20 PM
#6
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11-30-12, 05:51 PM
#8
Did you check the voltage at the alternator's output wire? When you stated that the voltage was dropping were you relying on the voltage gauge? If yes, then next time you see it dropping at the gauge measure it at the alternator and see if it matches or not as the gauge might not be accurate.
12-05-12, 12:26 PM
#9
Stuck On 7
Thread Starter
Did you check the voltage at the alternator's output wire? When you stated that the voltage was dropping were you relying on the voltage gauge? If yes, then next time you see it dropping at the gauge measure it at the alternator and see if it matches or not as the gauge might not be accurate.
12-06-12, 01:14 PM
#11
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Thread Starter
I was planning on taking the alternator out and taking it to autozone to get tested if not then the bad ground was next on my list. ill update as soon as i check both of those possible issues. where would i look for the ground for the charging system?
12-06-12, 01:49 PM
#12
Follow the negative ground cable down to the driver fender and it bolts to that area. And testing the alternator is for the birds as there have been numerous board members who had the alternator checked and it passed but never passed the mustard when actually in use. And many members upgrade to an FD alternator as it puts out much more amps.
12-07-12, 11:48 AM
#13
Stuck On 7
Thread Starter
Follow the negative ground cable down to the driver fender and it bolts to that area. And testing the alternator is for the birds as there have been numerous board members who had the alternator checked and it passed but never passed the mustard when actually in use. And many members upgrade to an FD alternator as it puts out much more amps.
12-07-12, 11:55 AM
#14
Then why were you talking as if the alternator was an S4? Confusing. Chances are the FD alternator either has an overdrive pulley or an underdrive pulley. The underdrive will cause the alternator to produce less voltage while idling but produces enough output while driving and the overdrive one would tend to produce enough while idling but tapers off some while driving and from the way it sound you have the underdrive pulley.
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