Gauges sporadic, thoughts?
04-16-2010, 08:19 PM
#1
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Thread Starter
Join Date: Feb 2010
Location: Johnson City, NY
Posts: 131
Gauges sporadic, thoughts?
Just figured that while I was slowly cursing my other luck in life, I would toss this issue to the masses, and see what thoughts I can get on it.
I have a 93 Z-28, A4, low 100k miles. The current situation of the dash guages, are as follows:
Temperature gauge is not working at all. I did notice the sensor under the exhaust manifold connecter was broken, so it's friction-fitting at the moment. Possibly a bad sensor to that, I figured. The connection IS tight, but no movement on the guage, regardless of run time. If not the sensor, I don't know what else I should be suspecting.
The Tachometer seems to be REALLY jumpy, at least in Park/Neutral. If I rev the engine up, it revs fine, but the guage starts jumping all over once it hits about 2500 RPM. Drops down, jumps back up, never really goes above 3k on the guage. This only seems to happen in neutral/park. When in drive, it seems to operate perfectly fine. Car runs fine as well, not skipping or hesitating, regardless of the tach jumping.
Other guages (Oil, Volts, Gas, etc) seem fine.
I do see an MSD coil in the car from the previous owner. However, I haven't had a chance to figure out the wiring setup for the LT1, so I have no clue what all the check for tach input, if it's at the box, the ECM, etc. Obviously still looking through other posts and sites and things, but if anyone can either point me to one directly, or just shout out here and lemme know where to look and what at, that would be awesome.
The only other thing I can think of, is perhaps the cluster is just...dying? I dunno, not something I've had happen very often. I guess in theory I could get an aftermarket tach from my step-bro and hook it up temporarily and see if I have the same issues. I dunno.
Thoughts?
I have a 93 Z-28, A4, low 100k miles. The current situation of the dash guages, are as follows:
Temperature gauge is not working at all. I did notice the sensor under the exhaust manifold connecter was broken, so it's friction-fitting at the moment. Possibly a bad sensor to that, I figured. The connection IS tight, but no movement on the guage, regardless of run time. If not the sensor, I don't know what else I should be suspecting.
The Tachometer seems to be REALLY jumpy, at least in Park/Neutral. If I rev the engine up, it revs fine, but the guage starts jumping all over once it hits about 2500 RPM. Drops down, jumps back up, never really goes above 3k on the guage. This only seems to happen in neutral/park. When in drive, it seems to operate perfectly fine. Car runs fine as well, not skipping or hesitating, regardless of the tach jumping.
Other guages (Oil, Volts, Gas, etc) seem fine.
I do see an MSD coil in the car from the previous owner. However, I haven't had a chance to figure out the wiring setup for the LT1, so I have no clue what all the check for tach input, if it's at the box, the ECM, etc. Obviously still looking through other posts and sites and things, but if anyone can either point me to one directly, or just shout out here and lemme know where to look and what at, that would be awesome.
The only other thing I can think of, is perhaps the cluster is just...dying? I dunno, not something I've had happen very often. I guess in theory I could get an aftermarket tach from my step-bro and hook it up temporarily and see if I have the same issues. I dunno.
Thoughts?
04-17-2010, 06:17 AM
#2
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Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 70,648
The 93 tach is different from all other years. It is driven off the coil, via a "filter". All the other years take the tach signal from the PCM.
Key on, check the voltage on the single wire that attached to the temp sensor in the head. Measure the voltage from the harness pin to the head. You're looking for 12V. If you have voltage, and holding the broken connector firm on the sensor, the gauge doesn't move, its probably the sensor. Shoebox has a procedure for checking the sensor:
http://shbox.com/1/4th_gen_tech2.html#ect
One final check - make sure the ground strap from the bolt that holds the IC module/coil bracket to the chassis is in good condition.
Key on, check the voltage on the single wire that attached to the temp sensor in the head. Measure the voltage from the harness pin to the head. You're looking for 12V. If you have voltage, and holding the broken connector firm on the sensor, the gauge doesn't move, its probably the sensor. Shoebox has a procedure for checking the sensor:
http://shbox.com/1/4th_gen_tech2.html#ect
One final check - make sure the ground strap from the bolt that holds the IC module/coil bracket to the chassis is in good condition.
04-18-2010, 11:20 AM
#3
Registered User
Join Date: Nov 2009
Location: Colorado
Posts: 10
CharlzO, I've had a similar problem with sporadic gauges (see https://www.camaroz28.com/forums/sho...d.php?t=745866). Nothing seems to be wrong mechanically, as I've already replaced the associated sensors. I'm gonna try a new approach today.
A few weeks back I had the dash apart, and noticed the electrical connection to gauges was absolutely soaked in old dielectric grease. It was from pin to pin - all over the place. That's when I thought... Maybe if I clean this crap up, my gauge gremlins will go away... So yeah, worth a try anyway. Shoulda cleaned it up back then.
Let me know if you try it, and if your tach goes back to normal.
A few weeks back I had the dash apart, and noticed the electrical connection to gauges was absolutely soaked in old dielectric grease. It was from pin to pin - all over the place. That's when I thought... Maybe if I clean this crap up, my gauge gremlins will go away... So yeah, worth a try anyway. Shoulda cleaned it up back then.
Let me know if you try it, and if your tach goes back to normal.
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