goose guy

2009 rx8 GT 26k miles, no mods except wheels.

Ok, I had a misfire so dealer changed 1 out of four coils and changed all 4 spark plugs.

Brought it back for CEL. Codes were:

P0506 - Idle Air Control System RPM Lower Than Expected
P0300 Diagnostic Code - Random Misfire

They checked coils, compression, fuel pressure. Ok. Then they cleaned the throttle body which had carbon build up. That cleared the codes.

So the car runs fine, except idle is now at 1000.

Problem is, idle jumps from 1000rpm to 1400rpm and back down again every 10 second ONLY WHEN AC IS ON. I've read some posts regarding neutral safety switch and clutch switch. Idle surging occurs when in neutral and when the clutch is pressed in as long as AC is running. If AC is OFF, idle is constant at 1000rpm.

Any ideas? I'm bringing it back to dealer but I would like to be informed so I don't get jerked around. Thanks.

Zoomingx8

Mine does the same thing but my idle is at 750-800 and it jumps to 1000 when the AC cycles. When it shuts off it will jump to around 1000 then when It turns on it will settle back down to 750-800

jasonrxeight

I am not experiencing any of these issues. hummm.

lta_ds_fs7

iTrader: (2)

Happens to me...Not up to 1400 rpms though.

Wingznut

iTrader: (1)

Are you still under the 3yr/36k warranty?

goose guy

yep...til 11/12. Car is at dealer now for that problem and to replace torn rubber button (for smart key) on door handle which is also covered under warranty.

When I brought it in yesterday, it was less pronounced. RPM blipped only to 1100-1150 and idle had settled to around 900.

Razz1

I believe the neutral switch surge causes surging without the AC on.

Time for you to bring it back to dealer.

Cars are suppose to idle higher when the AC is on but it seems like yours is jumping too much.

Bladecutter

Is your engine idling that high when the car is still cold, or when fully warmed up?

When my '11 is fully warmed up, with the A/C off, the idle speed will drop all the way down to ~850 rpms. It does do it in slight stages, though.

When I have the A/C on, it might take a bit longer to drop down to idle speed when coming to a stop, but then the idle is usually around 900 rpms, and will go up a touch, to maybe 950 when the A/C cycles on.

If I can remember later, I will take video of the tach for you later today.

BC.

Zoomingx8

It seems to be doing better now, now it doesn't even hit 1,000 anymore. I did do the ecu reset after I cleaned the maf and a few other things so It may have had to just re learn the air to fuel ...

goose guy

I think you're right. Got it back from dealer. They did extensive testing and a long road test and they found nothing wrong with the idle. ECU probably had to re-learn the settings like you mentioned.