specialop

I have a 1990 automatic convertible. I've been slowly bringing this gem back to life as I purchased it from a used car dealership for cheap. My problem is this: When the rpm gauge works, the car runs terribly. It makes a rattling noise and will lose huge amounts of power after 4000 rpm. It will also hesitate on acceleration, as well as sometimes stall in drive and reverse when the gas is barely depressed. When the rpm gauge does not work all off these problems go away and the vert runs amazing.

SpeedOfLife

iTrader: (16)

there are likely many things wrong with the car, but you should start with a full tune up and maintenance routine and also search this forum for grounds. you probably have terrible engine and ECU grounds, which can cause some of these problems. you may also have clogged injectors and or a clogged cat.

NoDOHC

The tach gets it's signal from the trailing coils.

I think I understand you to say that the tach works intermittently, and that when it works, the car hesitates and makes no power, but when it does not work, the car runs fine.

I am guessing that SpeedOfLife is correct in diagnosing it as a bad ground or wiring issue. It appears that something in the trailing ignition circuit is faulty.

I wish I could help more, but I would remove and clean all the grounds (engine block ground and ecu ground.) I would also try unplugging the two-wire connector going to the trailing coil pack (the one up by the brake master cylinder) and seeing if that helps.

This is an interesting problem, I will be interrested to find out what is wrong.

Hailers probably knows exactly what is wrong.

specialop

I hadn't thought about the grounds. I will clean them and see. Run some sea foam? Injector cleaner? I thought that the cat could be the rattle noise, but when the rpm gauge stopped working and the noise stopped, I was confused.

specialop

I disconnected the two-wire connector and the car ran very well and the rpm gauge didn't work, but when I reconnected it the car ran poorly again. ?

NoDOHC

It is something with your trailing coil then, I wish I knew a little more about how it works, but it seems that the trailing coil is bad. I wish someone who knows more about this would say something, because I am out of ideas.

If you happen to have a spare coil pack lying around (which I doubt) you could try it in place of the existing trailing pack. I always hesitate to buy parts unless I am pretty sure they are the problem.

You can probably run the car ok with that two wire plug removed and carefully taped. This will allow you to see if the symptoms are ever repeated with that plug disconnected and maybe this will help someone troubleshoot further.

I wish that I could help further, but you have reached the end of my experience. (I have never known one of these coils to fail in my years working with RX7s.)

I wish you the best of luck

SpeedOfLife

iTrader: (16)

many people have operational spare coil packs lying around and are willing to sell them for $30 shipped or less if you want to look for some. there's also a ground where the trailing coils mount to the body, you should clean that one up, lube it with dielectric grease, and replace the bolt and see if that helps any. I'm not exactly sure if that's where the trailing coils ground, but it would make some sense if they do and it's one of the easiest grounds to address.