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I have a 1990 Coupe deville w 69k miles, and it's not firing all eight cylinders. It only fires #'s 1,7,4,6. Why not the other ones?:banghead: It has new plugs,wires, cap,rotor,O2 sensor, and MAP sensor. I thought it might be the injectors, but now I'm not sure. Is there a sensor that I am missing somewhere:hmm: . Please help
 

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On the '90 (OBDI) you should be able to enter the onboard diagnostics and then go into the overrides and disable the injectors one at a time. If any are disabled and make no difference in the idle, then you know there is a problem there. A "noid" light will test the circuit to see if the injector is getting a signal to open (regular 12v test lamp will not work) or a stethescope works very well to listen to the injector and tell where or not it is operating. If you listen to one that is working you can easily hear it operating and you'll know what to listen for on the others.
 
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