Electric Noise PIC problem

[Tobias]

Three attachments, first is the schematic and the second is data from a logger box. The schematic is a simplified version. The data is sampled at 100hz, logger limited. The last attachment is a data sheet for an OPTO-MOS on the board

I have a box that is triggered by wide open throttle. At wide open throttle a timer starts and turns on outputs based on user set times. I am having a problem, I think with the wide open throttle getting noise and making the PIC think it lost the wide open throttle signal and resetting the timers.

The wide open throttle signal (16v) goes through a OPTO-MOS relay. The relay pulls down a pin on the PIC. The output when activated turns on another OPTO-MOS relay that turns on a P-Type mosfet. I have a DC/DC isolated power supply on the board and every input and output is optically isolated.

There are four traces on the data.pdf. The green wire is the output of the OPTO-MOS connected to the wide open throttle . When the OPTO-MOS receives 16v, the green trace goes low. This activates the timing sequence. The first output is programmed to trigger at wide open throttle and the second output activates at 1.2 seconds. So the yellow trace is the output of the OPTO-MOS triggering the MOSFET. The red trace is the output of the first MOSFET. The blue trace is the output of the second MOSFET. You can see the blue line going high at 1.2 seconds.

Keep in mind this data is being logged at only 100 hz. The data looks great until around 2.3 seconds. The red and blue trace go low. The red trace then goes high again and then flickers off twice before staying high. The entire time the 16v input is high. The last flicker is at 3.46 seconds and the second stage goes high at 4.66, right at the correct amount of delay from first stage activation.

This system works great on a test bench. I do have an ignition system on my test bench to simulate the engine running. However with cylinder pressure from the engine, there is more noise in a race car.

I know the PIC isn't resetting. There is about ten seconds after power up for the device to be ready to activate based on Wide Open Throttle.

Somehow the PIC is losing the Wide Open Throttle signal and restarting the timers.

Any suggestions?