BajanMX5

iTrader: (1)

I've come to my wits end trying to troubleshoot this problem with my miata by simply searching forums and google, so I've turned to the community for help.

The car is a 1993 California Spec 1.6L NA miata as stated in the Thread Title.

The problem:
The car starts and idles fine when cold or warm, however when at operating temperature, there is a random/intermittent but extremely drastic loss of power, both when accelerating and cruising.

A bit of background information:
Driving around on the stock ecu I experienced the loss of power, which, upon searching, I found could have been caused a number of things including: the afm (controlling the fuel pump), fuel pump itself, fuel filter, dirty fuel tank, coolant temp sensor, clogged catalytic converter, ignition leads, coil packs, oxygen sensor or coil packs.

I systematically ruled out each one as I replaced the 02 sensor, fuel pump, clt temp sensor, ignition leads and spark plugs, fuel filter and had the tank removed and cleaned.
These changes helped the general running of the car and improved the idle, however the mid-high rpm loss of power was still there.


The next step I took was to build a DIYPNP N76 kit for the car and installed that in place of the stock ecu; I did this to eliminate the airflow meter and determine if the cam angle sensor was the culprit causing loss of sync. Unfortunately it wasn't that easy and the cam/crank signals are clean so it's not the cam angle sensor.


As I continued to daily drive the car, eliminating possible causes as I went along, I found as the problem persisted, the only consistent thing I could see, was the coolant temp rises when it has the loss of power and there was coolant loss when I checked fluids after a long drive.

Next step was to assess the engine, so I pulled off the head to check the head-gasket and bottom end, which were both in pretty good condition.
Gonna do as thorough an inspection as I can without making too much work for myself to put it back together, and then re-install with arp studs and a mls gasket for a sense of security as I plan to boost the engine once the issue is resolved.

This brings you up to where I am now...lost.

Not sure what else to check but I'm going to try my ignitor and coil packs on a different car and refresh the head while the engine's apart.


Any ideas/suggestions would be greatly appreciated guys.