mx5cartalk.com

Could some wise person shead some light for me. Mine is a 98 NB8A with a highly modified normally aspirated engine (new).
Just run in and gave it a good run at Winton. I normally run it to 8000rpm with no issues, but because it's fairly new (1500 kms) limited it to 7500 rpm. Occassionly l was getting a slight miss at about 6500rpm with the tachometer needle bouncing. New plugs, comp ht leads, throttle body sonic cleaned, cam angle sensor and crank angle sensor standard, as is fuel pump.

What ECU is in it? Is it rev limiting by cutting spark?

Using a Microtech LT10s

I was thinking that if the ECU was cutting spark then the tacho would bounce around if the tacho is still dríven off the coilpack. If the tacho is dríven off the ECU then that's another matter.

When I had problems with my coiack, my doctor said I should eat more fibre.

Consider the ignition trigger.

I had exactly the same symptoms. Rapidly deteriorated (the next run on the track that day it was much worse). I had blown one of my Toyota COP coils. New coil, all fixed.

bruce wrote:When I had problems with my coiack, my doctor said I should eat more fibre.

Hahahahahha , damn doctors, what would they know.

As Dann said look at the cam/crank trigger sensors. The tacho is ECU dríven, not coil dríven so if you are getting a misfire and the tacho is dropping out then it is most likely one of your trigger sensors is dropping out.

Thanks for the constructive responses as well as the smart arse ones.
Not a great typist with one finger on an iPad. Sorry guys.
I'll check trigger sensors first before going onto coilpack