I got 99 miata with rev ms2v3 install in my car 4 days ago and now my rpm gauge jumping all the time and sometime it just sit at 0rpm with car running. When I hook up the laptop rpm reading at 850rpm what it suppose to be. I don't know what wrong w it can someone help out thanks

 

Check your electrical grounds, take some sandpaper to both surfaces & clean 'em up then snug the bolt on.
One on the driver's side of the throttle body, one underneath the brake master cylinder area. Probably a few others that people could recommend. Make sure your battery cables are clean/tight as well.

 

It was fine on the first few days when I install it. I have 99 miata w 01 gauge msm turbo, 305cc injector, and toy cop wire as wasted spark

 

Mine actually did this a few times right after I got it installed. But it quit doing it after a day.

 

I had another customer with the same problem, about a year ago. He sent me his ECU back, tested fine on the stim/bench. Then I went ahead and tested it on an actual car - the problem appeared roughly after 20 minutes of idling (whereas I could leave it running on the bench for an hour or more with no problems at all).

Since it didn't show on the bench, and I didn't have the same '99 car to test on again, I just replaced the entire expansion board and that solved it per the customer.

If you want to replace the 3 components that make up the tacho circuit, I can provide instructions so that you don't have to send me the ECU back.

 

Yeah can u sent me the instruction to antransj@gmail.com I'll see if I can do it without breaking anything. Thx

 

I figured out what's wrong... The back of my gauge all the solder for tach is melted and migrate down to the bottom of the circuit causing that noise on tach lol replaced w my old gauge everything work fine now

 

Good to know.

 

whoa, someone actually posted a follow up?!

 

Lol