Posting here to add to the knowledge base.

I have a F20C running on a stock ECU in my race car.

At my last race meeting I noticed the car starting to get intermittent vtec, which quickly degraded into no VTEC with the bonus that it would fall into limp home mode if I tried to drive it > 6500rpm.

I thought it could have been because of an overvoltage as i had my kill switch play up in the same session the problem started.

I replaced the knock sensor and whole vtec switching assembly and check the wiring, then I cracked open the ECU.

It wasn't due to the bad kill switch. Just a coincidence.

The problem was that the VTEC switching IC ( a specially packaged transistor setup) is standing free from the main circuit board with nothing supporting it. Under race conditions in the orientation that I had the ECU mounted the long term vibration caused brittle fatigue of the components legs causing two to break.

I traced the problem to an open circuit on this component. It wasn't till I started to desolder it I found the two legs that had brittle fatigued. It was almost impossible to see until I got some heat onto the solder joints on the circuit board.

The component was SK5151S and was available from an online seller in the US for $7 plus $3 postage.

Have now mounted the ECU with rubber vibration isolaters, and used a hot glue gun to tie the component to the one next to it , and to the circuit board at its base.

Hopefully this is a rare problem, hopefully this info will help someone who has the same symptoms.

 

Wow, great failure anaylisys. Good info, thank you.

You don't have the ECU mounted in the stock location?

 

He has a Lotus 7 replica with an S2000 motor. So no, its not mounted in the stock location!

 

Not really stock in any manner.

 

Sick!!!