Rough Idling

Technical Area Engine, Transmission, Exhaust etc
1
  1. My model of MX-5 is: 2.0L Kendo Electric Roof Year 2011 (61) - 44k miles.
  2. I’m based near: Carlisle
  3. I’m looking for technical help or recommendations on: rough idling moving between 700 and 900 rpm repeatedly today - had been idling beautifully since purchase July 2018 with 31k miles. Car not used for few months on the drive, recharged battery and started OK idling OK for 2 weeks till this morning… Tried to leave it idling 2 hours hoping ECU will “reset” to no avail. Regularly serviced (annually).
2

Charged battery on or off the car and was it absolutely flat?

Have you been anywhere in it (miles) or have you just left it idling on the drive?

I would as a first call drive the car if you haven’t (restrictions permitting) a few miles it could well need it if you haven’t already done so.

As a second try disconnect the battery and do as above, hope you’ve got the radio code some need them if you have the original head unit.

3

My NC1 has a really lumpy/wobbly idle following a battery disconnect or change. To the point that it feels like it’s on the brink of stalling when pulling up to junctions. It’s happened quite a few times, and usually sorts itself out after sitting on the drive and idling for 20-30mins and driving around for 50-100miles. It’s never been an exact science for me but it seems to correct itself after a week or so by combining the above.

4

There should be a sequence to go through listed somewhere on here in order to stabilise idle speed after a battery change.
Try searching for “idle speed”

5

I’ve had my battery off numerous times, the leave idling fix is the one that works best.

6

Thanks and good to know! :sunglasses:

7

Here you go!

“Put the key in position 1 for one minute turned off 1 minute…started car let Idle for 20 minutes then turned every electrical item on and let Idle for another 5 minutes…then did the DSC reset then went for a 20 minutes drive,…it now drops and stops at 800 like hitting a brick wall…best it’s ever been since purchased a couple of months ago…fingers crossed it stays this way”

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8

That’s my write up thought I recognised it… :grinning:

Also make sure terminals really tight.

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9

I actually have it written on a piece of paper kept in my centre console for future reference