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I have a heavily altered 90 ZR1. The last couple of time I took it for a spin the speedometer came on and of. When it reads "O" the thing is kind of wimpie, the instant it comes back on the thing breaths fire. Is my problem with the prom or the speedometer?
thanks
Ronnie.
I can imagine that if the sending unit on the speedometer is acting up, then the power control module would be getting improper info and would set itself into some default safe setting that would be lacking in performance. However, I suppose it could just as easily be PCM intermittantly failing to read and process the signal assuming the speedometer transducer is working all of the time.
Shop manual should have a trouble shooting chart for the PCM. Not having worked on a C4 Vette, I can't tell you specifically what to try. Assuming there is a plug at the Speedo sending unit on the transmission, you might unplug it to see how the car responds. If is is similar your lack luster performance when the speedo is not working, then you might try a new sending unit. (again, assuming it has such a critter)
I can imagine that if the sending unit on the speedometer is acting up, then the power control module would be getting improper info and would set itself into some default safe setting that would be lacking in performance. However, I suppose it could just as easily be PCM intermittantly failing to read and process the signal assuming the speedometer transducer is working all of the time.
Shop manual should have a trouble shooting chart for the PCM. Not having worked on a C4 Vette, I can't tell you specifically what to try. Assuming there is a plug at the Speedo sending unit on the transmission, you might unplug it to see how the car responds. If is is similar your lack luster performance when the speedo is not working, then you might try a new sending unit. (again, assuming it has such a critter)
The chips likely would not be the culprit. They are essentially a storage area for some set parameters that the computer goes out and pulls data from. The speed sensor sends pulses to the computer which uses tht info along with a dozen other sensors to determine what the engine and vehicle is doing and adjusts the fuel, spark etc. The computer sends a signal to the speedometer readout. Vehicle should operate fine with out a speedometer readout. Problem is likely located in the speed sensor, wires to the computer or the computer itself. You likely will need a shop manual of some kind to identify the proper sensor location.
The chips likely would not be the culprit. They are essentially a storage area for some set parameters that the computer goes out and pulls data from. The speed sensor sends pulses to the computer which uses tht info along with a dozen other sensors to determine what the engine and vehicle is doing and adjusts the fuel, spark etc. The computer sends a signal to the speedometer readout. Vehicle should operate fine with out a speedometer readout. Problem is likely located in the speed sensor, wires to the computer or the computer itself. You likely will need a shop manual of some kind to identify the proper sensor location.
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