So, I recently acquired an 85 rx7, with the 12a. I've been driving it daily for about 2-3 weeks now, with no significant issues until tonight. I went to start the car to go home, and as soon as the key got passed the ACC position, the high rev buzzer started to sound and would not stop until the key was turned off. The sound continued while starting the car and while the car was running. This wasn't too odd in and of itself, but there are other things that started to happen that hadn't prior to this buzzer issue.

The other things that started happening tonight for the first time are, the tachometer does ant accurately show the rpms. At idle, it is where it should be, but as I would accelerate the tach would only go up a fraction of the way. Ie, at what I would guess was about 3000rpm, it still showed only around 1500rpm.

Also, when I would reach what the tach was saying was 1500rpm, the buzzer sound would go from the typical constant high rev buzzing to a pulsing buzz. The pulse started slow, and would increase with increased rpm, and decrease as the revs came down to approximately 1500 and hen it would just stay a constant buzzing.

In short,

-high rev buzzer starts as soon as the key is turned past ACC, and continues to buzz until engine is off and key is turned off.

-tach is reading lower than current rpm at above idle, showing approximately 1500 rpm when it's approximately 3000 actual rpm

-buzzing sound starts to pulse at approximately 3000 rpm, and the frequency of the pulsing increases with increased rpm.


I've tried disconnecting the battery and reconnecting it, and the fluid levels all seem okay. The coolant is a little low, but no lower than it has been the past two weeks of daily driving. I've done a bit of reading but cannot find a thread that describes all three of my connected symptoms. Any guesses, or on anyone on here live in Maine?

 

Have you tried disconnecting the oscillator?

In damp weather they sometimes malfunction and cause the warning buzzer (more like a screecher) to sound.

Look for a small rectangular black box attached to the engine bay in front of the battery, it usually says "oscillator" on it. Locate the electrical black connector and pull it off.

If the screeching stops that was your problem, at least at least for the screeching, not sure about the tach issue, might or might not be related.

 

I'm with Ray on this one. The oscillator controls the warning buzzer for low oil pressure and low coolant level. You could be experiencing one of those two conditions or the oscillator is on the fritz. Check your fluid levels and then remove the battery and check the oscillator for water damage or corrosion on the connector and pins.