Jump Tach On 85 Gsl
04-09-2003, 01:59 AM
#1
Senior Member
Thread Starter
Join Date: Jan 2003
Location: Under the hood in Sioux Falls
Posts: 106
When my car idles, the tach jumps from 600-900 rpm's. I heard it was the BAC valve and/or throttle position sensor. It also does it when im in a high gear and a low speed, ie. 35 and 4th gear, then i hit the gas and it jumps about 5-700 rpms, otherwise it's fine.
04-09-2003, 03:20 AM
#3
Senior Member
Thread Starter
Join Date: Jan 2003
Location: Under the hood in Sioux Falls
Posts: 106
The engine and other gauges are just fine, the tach jumps. Performance and idle is just the same. It did it a while ago before i got my clutch changed. But it just returned and always catches my eye at stop lights or accelerating in a high gear. 
04-09-2003, 10:03 PM
#7
Senior Member
Join Date: Nov 2002
Location: Bakersfield, California
Posts: 569
You might also want to hook up a timing light to the trailing coil wire, tape the trigger
down and aim it inside the car. Then sit in the car where you can see both the light and the tach. Start the car and watch both.
If the tach jumps with the light steady, look for breaks in the wiring loom after
the trailing coil.
If both jump/act funny at same time, look for breaks between dist and coil.
Especially near where it goes over the A/C compressor.
Hope that helps
Raul
down and aim it inside the car. Then sit in the car where you can see both the light and the tach. Start the car and watch both.
If the tach jumps with the light steady, look for breaks in the wiring loom after
the trailing coil.
If both jump/act funny at same time, look for breaks between dist and coil.
Especially near where it goes over the A/C compressor.
Hope that helps
Raul
04-11-2003, 02:15 AM
#8
Senior Member
Thread Starter
Join Date: Jan 2003
Location: Under the hood in Sioux Falls
Posts: 106
I just picked up a haynes repair manual today. First of all thanx raul and mike for the help but i noticed today my car was a little degraded(kinda hard to notice, maybe just the sea foam i put in with this last tank) in performance. Sometimes it's hard to tell, but when your oil pressure/level gets low can you feel degraded power and response? Maybe i have blown an apex seal. How could i tell for sure besides a compression checker? Is it possible to remove/relocate the 6 colored solenoid valves on top of the engine block? Cuz i think they're wack as hell.
04-11-2003, 02:30 PM
#9
Senior Member
Join Date: May 2002
Location: California
Posts: 22,465
Originally Posted by 85Daddy12A' date='Apr 10 2003, 11:15 PM
I just picked up a haynes repair manual today. First of all thanx raul and mike for the help but i noticed today my car was a little degraded(kinda hard to notice, maybe just the sea foam i put in with this last tank) in performance. Sometimes it's hard to tell, but when your oil pressure/level gets low can you feel degraded power and response? Maybe i have blown an apex seal. How could i tell for sure besides a compression checker? Is it possible to remove/relocate the 6 colored solenoid valves on top of the engine block? Cuz i think they're wack as hell.
mike
