I started up the RX-7 yesterday for the first time in a few months, and after charging the battery, it started right up. I was letting it idle for a little while to warm up while removing some of the interior behind the seats to dry out water under the carpet (just behind the seats, nothing was wet in front of them), when I noticed that the engine would hit what felt like a rev limit of ~4000 rpm when blipping the throttle. It sounded & felt almost like the launch control spark-cut limit. Over the course of about 10 minutes, this rev limit moved down in speed to the point where it would cut in at ~2000 rpm, and another few minutes later it was causing trouble at idle speed of 750 rpm. At this point I went inside to grab the laptop to datalog it, and when I got back outside the engine had died.

I plugged the computer in and started logging when cranking the engine over, and there was no RPM signal at all. TPS, MAP, MAT & CLT all seemed to be working. In the logs, no sync errors were logged, which seems to imply that both the 2-tooth & the 24-tooth sensors & signal processing circuits died at the same time, or the portion of the MS2 daughter card that interprets trigger inputs failed.

I made sure that the harness is continuous from the CAS plug to the DB39, and the CAS itself at least appears to be in good working order.

Im currently recharging the battery, as the cold overnight and apparently poor state of the battery is keeping me from even cranking the engine this morning. Once its charged a bit more I'll try to get trigger & tooth logs when cranking, but in the mean time, has anyone experienced a failure like this, or have any ideas about the cause?

Thanks a lot!

 

Oddly enough, when I plugged the MS back in this afternoon & cranked the engine over to get the tooth/trigger logs, it started right up & would rev up to the redline. Odd, but fortunate. Anyhow, I'll keep an eye on it when I start driving the 7 more

 

sounds like the battery/charging system was your cause.

 

Or there is a loose pin on the DB37. Ran into this before and it drove me insane.

Alternator noise as suggested is also high up in the list. If a rectifier has failed there will be a tonne of AC on the system.