tacho jumps when hot
 

Hi all I have registered to see if I can find some help with a new ecu problem im suffering with.....

On stock ecu the car runs like a champ, no issues other than occasional idle droop

On standalone ecu it runs great from cold but after getting the engine bay hot (after motorway run/long periods at idle) I'm finding the tach starts to jump, worse so when accelerating. What I have since noticed is that it is hugely injection related because in overrun fuel cut there is no jumping until injection resumes from either throttle input or criteria are met for fuel resume. Im also getting a false trigger/reset once/twice over the course of a long drive, fault is recorded as false sec trigger filtered

Im sure its an earth connection problem, something is different to the stock setup as it never does this on stock ecu. Also selecting reverse gear drops the tacho to almost zero! I currently have 2A & 2B connected together on a ground plane for "power ground", 2C is Ecu ground, 2D is sensor ground. I cant see what is wrong and its only a problem when hot which is odd, perhaps you could help? Ill most likely be asked....im using an unknown Ecu on a 94 eunos roadster

thanks

Dan

Jumping?

Yes jumps when accelerating and as soon as wideband registers fuel cut on deceleration it goes back to normal. It also drops when I select reverse gear which is odd. Much less extreme than your video,-mine jumps only about 500rpm maximum

Problem is only when the engine is hot after long idle or motorway drive

On wiring diagrams there's grounds at pins 1K (MT only) and 2F.....are these required?

All usual ground points are clean and tight

Anyone?