Hey all,
1995 chevy tahoe, 5.7 V8, 4x4, 4 door, LS....
Ok have had some electrical issues with the tahoe. brought it in to get checked and the mechanic said all tests he performed with the snap on scan tool read ok, the drop in voltage at a stop light were normal. all grounds were ok and all positives were ok (that he checked) i wound up having him install a separate voltage meter under the dash. He connected the power to a block under the dash (directly next to the buzzer that sounds when key in ign. and door open, lights on and ign. is off etc..) for accessory male blade. This one seams to have power when ign. switch is on only, there is a male blade under that one that has volts all the time. when he installed the meter it read slightly higher than the dash meter and was more sensitive where when hitting the window down switch you could see a drop in voltage quickly and would return quickly when letting off the window switch.
I wound up replacing the alternator with a summit racing tuff stuff high output alternator/optima yelow top battery and noticed a great improvement with the lights not dimming at a stop light.
Recently when starting in cold whether and cold engine-----
1.Ign. key on but not cranking-----volts are at 9volt for a few seconds then jump to just above 12volts by looking at both gauges. (why would this happen?)
2.start the engine-----volts are erratic jumping between 13 up to 15.5 or so. If I put on the headlights I can actually see a strobe affect on all the exterior lights and dash lights where they are getting surges of power. If I turn on blower motor, lights, rear defogger the volts go down a bit but are still erratic then when i hold the gas peddle down slightly to 700 to 1500 rpm more times then not the volts even out around 13 to 14.5 ish. when i let go of the peddle the volts drop then are erratic again. Let me go back and say the new volt gauge jumps all around but the guage on the dash stays steady but close to 15volts. After the truck warms up the problem seems to go away. but i did get a higher voltage code#35 Map sensor so this made me think not the map sensor but a high voltage issue with the truck.
So far I ran to the engine compartment and just after starting checked the volts at the battery and it was receiving around 14v up and down .10 to .30. the alternator was putting out the same (I have two positive lines from the alternator to the battery and two negatives from the battery to the body). I checked the volts at the fuse block in the engine compartment and it read pretty much the same as the battery just slightly lower.
The meter i am using is a radio shack digital so not sure if it can keep up with the volt changes the analog meter inside the truck as far volt swing and how fast it is happening.
I have a new slightly used alternator I was thinking about swapping I think it is a 105amp with a smaller pulley to create more amps at lower rpm? not sure if the alternator with internal regulator could be the culprit or if there a a short somewhere?
would the ecm possibly cause this? I have had other issues I think corrected was getting bad egr fault, bad IAC fault, #59 trans fluid temp below -40. replaced egr and IAC, they have not come back. HAd to replace distributor due to Pick up coil went bad and really thought it was ICM because ever ICM i put in truck ran great till 4 miles then died but i must have temporarily moved the wires for the pick up coil and it worked for short burts, test pick up coil wires and ohms were all over when moving the wires slightly so that was the fault not the ICM. reset timing properly or at least very close to 0 TDC. can't get a good read on the damper where the marks are but from pictures I got it close.
Other issue I still have is it is a hard cold start. turn key on wait few seconds for fuel pump, crank for about 20 seconds to start or key on wait few seconds, crank for few seconds, stop, crank again and starts right up.
1995 chevy tahoe, 5.7 V8, 4x4, 4 door, LS....
Ok have had some electrical issues with the tahoe. brought it in to get checked and the mechanic said all tests he performed with the snap on scan tool read ok, the drop in voltage at a stop light were normal. all grounds were ok and all positives were ok (that he checked) i wound up having him install a separate voltage meter under the dash. He connected the power to a block under the dash (directly next to the buzzer that sounds when key in ign. and door open, lights on and ign. is off etc..) for accessory male blade. This one seams to have power when ign. switch is on only, there is a male blade under that one that has volts all the time. when he installed the meter it read slightly higher than the dash meter and was more sensitive where when hitting the window down switch you could see a drop in voltage quickly and would return quickly when letting off the window switch.
I wound up replacing the alternator with a summit racing tuff stuff high output alternator/optima yelow top battery and noticed a great improvement with the lights not dimming at a stop light.
Recently when starting in cold whether and cold engine-----
1.Ign. key on but not cranking-----volts are at 9volt for a few seconds then jump to just above 12volts by looking at both gauges. (why would this happen?)
2.start the engine-----volts are erratic jumping between 13 up to 15.5 or so. If I put on the headlights I can actually see a strobe affect on all the exterior lights and dash lights where they are getting surges of power. If I turn on blower motor, lights, rear defogger the volts go down a bit but are still erratic then when i hold the gas peddle down slightly to 700 to 1500 rpm more times then not the volts even out around 13 to 14.5 ish. when i let go of the peddle the volts drop then are erratic again. Let me go back and say the new volt gauge jumps all around but the guage on the dash stays steady but close to 15volts. After the truck warms up the problem seems to go away. but i did get a higher voltage code#35 Map sensor so this made me think not the map sensor but a high voltage issue with the truck.
So far I ran to the engine compartment and just after starting checked the volts at the battery and it was receiving around 14v up and down .10 to .30. the alternator was putting out the same (I have two positive lines from the alternator to the battery and two negatives from the battery to the body). I checked the volts at the fuse block in the engine compartment and it read pretty much the same as the battery just slightly lower.
The meter i am using is a radio shack digital so not sure if it can keep up with the volt changes the analog meter inside the truck as far volt swing and how fast it is happening.
I have a new slightly used alternator I was thinking about swapping I think it is a 105amp with a smaller pulley to create more amps at lower rpm? not sure if the alternator with internal regulator could be the culprit or if there a a short somewhere?
would the ecm possibly cause this? I have had other issues I think corrected was getting bad egr fault, bad IAC fault, #59 trans fluid temp below -40. replaced egr and IAC, they have not come back. HAd to replace distributor due to Pick up coil went bad and really thought it was ICM because ever ICM i put in truck ran great till 4 miles then died but i must have temporarily moved the wires for the pick up coil and it worked for short burts, test pick up coil wires and ohms were all over when moving the wires slightly so that was the fault not the ICM. reset timing properly or at least very close to 0 TDC. can't get a good read on the damper where the marks are but from pictures I got it close.
Other issue I still have is it is a hard cold start. turn key on wait few seconds for fuel pump, crank for about 20 seconds to start or key on wait few seconds, crank for few seconds, stop, crank again and starts right up.
