Idle issue - is it normal ?

Technical Area Engine, Transmission, Exhaust etc
2

Hi,

Has anyone else had a similar problem / issue to me…

I’ve a low mileage NC 2.0 - 2006 with Full Mazda history which has decided to misbehave on tick over.

The car was last serviced 3 months ago and seems in fine fettle, goes well and seems a sweet thing with only 26,000 miles on the clock.

Randomly the rev counter needle decided to swing about between 400 and 900 rpm, almost stalling, no real difference between hot or cold use.

Starts and runs fine through the range, just swinging around on idle.

Gave it a good old run around and the idle seems a bit more stable now, just a bit of a swing between 800 - 900 rpm on idle.

I changed the air filter for a fresh one, checked all the hoses and connectors - all fine.

Tank topped up with some Shell V max and it runs well…except I get the odd flutter on idle, then it settles down. I can’t remember ( and I can’t find a figure ) but I think it did idle at about 900 rpm, it’s now dropped to 800 ish rpm. Not much, just enough to make me think it’s a tad low.

I haven’t disconnected the battery or messed about with anything else - I’ve read similar posts with a similar issue after changing the battery.

The car is under warranty with Mazda, so I gave them a call locally…" they all do that Sir, it’s a common fault, give it a good old thrash and it will be fine".

It’s had a good run around now … I have some uneven idling, plus I’m sure it’s idling a tad lower than before…so better but not as before.

Any clues ?

Should I be taking it in the Mazda to check ?

Do they all do this ? ( it was spot on before - no issues )

There are no warning lights on the dash and it’s runs really well otherwise…just seems a bit odd.

Thanks for your help - jr

 

 

3

Idling at 800rpm sounds about right to me. I’d let the dealer see it though if it’s under warranty. If it is fluctuating by 100rpm, then that sounds like quite a lot.

4

Thanks Robbie…I will keep an eye on things this week and have a chat to Mr Mazda if it’s still misbehaving.
Cheers for now - jr

5

I had this erratic idling for a few miles and it nearly stalled once.

I put it down to disconnecting my battery, I had taken the head unit out to remove the DAB unit and add a iPod link.

I remembered I had read somewhere if I’m correct that the ECU has to re learn the fuel delivery etc, so I gave it a run, infact we went for a drive of around 70 miles and all is well now back to normal.

Not suggesting yours is the same but would it be worth disconnecting the battery for a while and see if that works. Maybe Robbie can advise if it’s wise to do. Apart from resetting the radio and window settings then just the DSC to reset afterwards.

6

No harm in disconnecting the battery, I personally have not experienced idle concerns after battery disconnection.

7

My mk3 1.8I 2006 plate has exact symptoms as you have described I would like also to find out about this car runs fine just when I come to traffic lights ect the rpm needle jumps up and down nothing over 1000 rpm as If it’s going to stall but it dosent

8

I also don’t know why my reply copied so many times it’s like my rev counter lol

[size=2]Duplicate posts removed by mod[/size]

9

I was just about to say the same, erratic PC.

No harm in a battery disconnect, it may do the trick.

10

Thanks guys…
It was playing up again this evening, all over the place when cold, less so when warmed up.
It is really annoying !
I am going to bite the bullet and book in into my local Mazda dealer, it’s under a 12 month mazda warranty, is I really have to start here I guess.
My thought was a dirty or failing idle valve or throttle body full of carbon deposits.
The car has just clicked onto 27000 miles…so it can’t have had that much fuel through it to really gum it up ?
Let’s see what Mazda have to say.
Jr

11

The other option is find somewhere quiet, in neutral hold the rpm at 3k after 3 mins or so the revs will suddenly drop to idle.

12

Steve is spot on, that’s the way to re set the ecu

13

Thanks for the advice… I will try the 3000rpm for 3 minutes reset before I call the dealer.
I’m guessing this is probably what they would try first too.

Is it better to warm the engine first ?
After the reset period the revs drop on their own… Sounds a bit strange, if I didn’t know I 'd think I’d broken it !

Cheers all - I will update on progress, it looks like it’s a more common issue than I thought.

:slight_smile:

Jr

14

I would do it on a warm engine, the revs will just drop after 3 mins or so, your foot will still be on the throttle when this happens. Then I presume the ECU will relearn.

15

I would have said that the revs drop after 3 minutes of fast idle to prevent the exhaust/catalyst getting too hot and then possibly melting surrounding componants due to lack of forward movement airflow.

16

I’ve just looked in an owners manual and it states not to operate the engine at high idle speed for more than 2 minutes, one of the reasons given is because the catalyst may over heat.

17

Hi I also have a mk3 2006 plate and when I stop at traffic lights ect my rev counter does the same drops like it is going to stall and then goes back to 900 rpm needle just jumps up and down I would also like to sort this out ?

18

Nobody has mentioned whether the air conditioning/climate control is running when these slightly unstable tick overs occur. I find my car ticks over in a more stable fashion when the A/C is off ( and it`s off most of the time now with the top down for this lovely weather!) I suppose this is to be expected, as one can hear the compressor cutting in and out varying the load on the engine.

19

No aircon or climate on or radio or Windows operated when this happens not even stearing wheel moved

20

Hi… I’ve done the deed… Booked it in for Mr Mazda to have a look at.
I came to the conclusion that the warranty cost enough, time to use it I guess.
Will report back on progress.
Thanks so much for your advice - I might go back to plan a if mazda start messing me about.
Jr