Here is the situation. While driving my tach will begin to jump all over the board erratically. when this happens the cars stutters and misrfires. My car was not throwing any codes.
I bought a new distibutor and installed it, the car ran fine for about 20 minutes then started the symptoms again.
A week later it threw code 1 oxygen sensor. I replaced the oxygen sensor with a new one. it ran fine for about 20 minutes then symptoms again. no more engine code.
I then bought another new distributor. With the same outcome ran fine then symptoms.
I then bought new denso iridium plugs.ran fine at first then problems.
Swapped out wires, ran fine at first. Then same thing.
I changed the fuel filter and problems continued.

Any help?? Still no codes since I changed my oxygen sensor.

 

i had a similiar problem to that. check the grounding on the thermostat