Hey guys,
I have a wierd issue that started 2 days ago. When I started my 91 Z, the SES light came on, car idled rough for about 30 seconds, Then SES went out. Car ran fine. The issue happened again yesterday and today, But these times I noticed that when the SES light went on (while driving) the speedo drops to 0 and the car seems to bog. Then cleared up after about 1 minute.
A little background on the car. 91 Z28 coupe, TOTALLY stock, Has not needed any work to the car since I have owned it. Car has just passed 22,000 miles.
I would like to avoid bringing the car to my Chevy dealer for them to fix it, and rape me for a $20 fix. Any input woult be helpful.

 

What code are you getting 24 ?

 

Have not pulled codes yet. the scanner I have is not compatible. I took a ride down to Auto zone, and they don't have the OBD1 scanner that is needed


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Well, I just "Paper Clipped" the code and it is coming back as 24.

 

http://chevythunder.com/vss_code_24_sd_199092.htm

 

Alright, finally replaced VSS, and. still problems. I still get intermittent SES light, but now speedo is totally inoperable. Even when SES is off and car running fine. I did notice today, that SES light did not go off at all during a 35 mile drive, and it was damp out. which makes me think that it may be a wiring issue. Any thoughts?


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Is your vss in the tranny or on the back of your speedometer?

 

Rear wheel speed sensor - it went away never came back.... yet.

 

VSS is in tranny. no bufferbox behind speedo.


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On your car, the VSS signal goes to the ECM 1st, then the speedo.

If you still have the VSS code then you are not getting the signal from the VSS into the ECM, as you note wiring is suspect.
A continuity check of the wires from the VSS to the ECM connector would be in order
Purple and yellow wires on terminals B9 and B10 on the ECM connector

http://www.chevythunder.com/199092_f...227730_ecm.htm

If you have no VSS code showing but no speedo then the wiring from ECM to cluster is suspect

 

Does this car have antilock brakes? Ran into a similar situation. Ignition switch had bad contacts that feed the VSS, brakes, and I think the heater blower. Yours may be different but similar. No power to speed sensor, brakes, really screws things up. Worth a look.

 

No ABS.( didn't think that any 3rd gens had ABS ) Going to to some wire checking over the weekend. I have a spare ECM laying around to check that too.




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The clip for the drive gear can break causing the gear to move away and not mesh with the driven gear, thus, no speedo.