HELP please - ECU blowing fuse repeatedly...

[pphilpot]

Hi All

I'm back again with my D9 1.8 Rapier (petrol 16v). Ever since I bought it a month ago it's been hesitating between 2500-3500 RPM. This is an intermittent fault - it goes for hundreds of miles, and comes back with a vengeance.

Now the ECU is blowing fuse 27. If I turn the ignition key to its final position before turning the engine over, then "POP", fuse 27 blows (with an audible pop with the bonnet and door open). When I replace the fuse it will still blow when I turn the ignition key again. When I disconnect the ECU and then reconnect it the fuse doesn't blow and the car starts - until it happens again a in few hundred miles time. This happened on Friday morning, and again this afternoon.

Does anybody know what could be causing such a large surge to cause this - and be temporarily solved by disconnecting and reconnecting the ECU?

Initially I wondered if it was some of the wiring to the sensors shorting out (and also causing the hesitation when driving), so while it was blowing fuses I tried disconnecting sensors and trying the ignition again - this just resulted in blowing the fuse again until I got to the ECU. Well actually it was the little box right beside the main ECU box whatever that is that stopped the fuse blowing when disconnected, but when connected again the fuse blew again until the main ECU connector was disconnected and reconnected - after that, no more fuse blowing.

Fortunately I had the foresight to buy a handful of 30A fuses...

I hope somebody on here has an idea or two as the missus is fed up with breaking down

Cheers all, and many thanks in advance for any help/ideas that you may have.

Paul

[pphilpot]

OK, so every time I post on here it encourages me to get back out there and get under the bonnet.

The problem is that wires have chafed causing a short - this appears to also be causing the hesitation.

It must be a design fault, so this may prove useful to others who have the hesitation problem. If you follow the loom from the ECU down behind the inlet manifold you'll get to where the wires for the throttle housing sensors come out of the main loom cluster. This is poorly positioned and mine was resting on a sharp metal support running horizontal to the loom. Years of movement had rubbed through the grey and white wires running to the throttle body sensors. I'll solder these tomorrow, and I'm certain that my fuse blowing, rough idling and annoying hesitation will be a thing of the past.

[Doggy]

Glad to hear you've got to the bottom of it - really no other way to find this kind of fault. If you're lucky you stumble over it eventually.

[steve_earwig]

And thanks for posting about it, as you say it could prove useful