mx5cartalk.com

Ok, first of all allow me to apologise as this does not relate to my MX-5 but my Ford Festiva.

- I replaced my battery with a new one.
- Idled lower than usual, and rather rough
- left it idling for 12 mins then went for a drive
- as soon at the car hit the mid-range, power faded considerably

The only way I can describe the loss of power is it's like I lost a cylinder, or like a complete opposite of \"coming on boost\" in a turbo car.

It would accelerate as per usual up till about 3,500RPM then the power literally plateaus. The engine would still rev as fast as normal, but the car just doesn't accelerate as fast as it should.

Any ideas?

Surely changing the battery wouldn't reprogram the ECU dramatically, would it?

Surely changing the battery wouldn't reprogram the ECU dramatically, would it?

Yep. Reset the base idle and then drive it as you used to.....could take a while (days) for the ECU to remember.

Thanks JBT.

The base idle cannot be reset. My mechanic and I tried all possible ways and it just doesn't move.

So what you are saying is I should drive \"energetically\" as per usual until the ECU figures out my driving style and programs the fuel and ignition accordingly?

Yes, that's about all you can do. Something is wrong if you can't adjust the base idle speed. You have to short out the TEN and GND terminals in the diagnostics box to do it or the ECU will just take control.

Festivas work a little differently to mx5s JBT
I would be checking for any blown fuses (if not already done so) and loose wires near the battery.

You may have unplugged something close by and it is necessary for the car to rev (maybe a vacuum valve or presurre sensor).

I once installed a battery back to front and blew the fusible link. Then proceeded to swear at everything on the car (and the world) until i realised what i did (i was feeling a little precious that night)...

It's cool now. Kinda.
The Festiva is starting to behave itself.

Ooops Went to the problem and missed the Festiva bit......guess I should have expected Festiva problems to be in the MX5 Engines, Transmissions & Final Drive section.

Hi 1red5,
I would perhaps check the bettery voltage prior to startup. I had a similar problem with a mazda 323 Astina a few years ago. Everything pointed to a dud idle stepper motor, but once I replaced the battery the problem disappeared. We finally figured out that the battery voltage prior to startup was too low to allow the idle stepper to find its true home position and therefore the stepper was not working properly.
Perhaps your new battery is not quite what it should be.
I may be completely wrong here, but its worth checking!
Hope this helps...
Cheers
Chris

Thanks for that Chris, I will keep it in mind.

The Feisty (that's her name) is starting to open up again.
If it plays up, then I'll be doing your check amongst other things.

Cheers

Andrew

which year Festiva?

i've still got a Gregorys autofix servicing manual here.

She's a 1997 TrioS Vu. WD 1.5L B5.
BTW have you installled your horn?

ah a WD.. i dunno then maybe try fordfestiva.com, they call the 2nd gen Festiva an Aspire in the U.S.

nah horns not in yet, it'll probably go into the replacement car soon enough though

but maybe it won't need it since the car does sneeze loudly

the US Festiva/Aspire forum has been a hit and miss affair. Not their fault though as they don't have the B5 engined ones there.