Idle dip on SE

blackster · Postby **blackster** » Thu Dec 14, 2006 9:22 pm

Havent really payed much attention to it until now, but ive noticed that then when the car's fan comes on, idle drops by about 200rpm then quickly makes it way back to normal. The same thing would happen when you operate the high beams whilst the lights are off or when holding down the power window button backwards.

Are other SE owners getting this?

Alf · Postby **Alf** » Thu Dec 14, 2006 10:24 pm

Not in mine in the last 58,000 km,

I'd suspect that either the battery is shot, not fully charged, or has a loose connection.

Mine's a daily driver, so the battery doesn't get too much of a chance to discharge, but if you're running an alarm and only drive it on weekends, for instance, there's a good chance the battery never gets fully charged.

Cheers,
Alf

Andrew · Postby **Andrew** » Thu Dec 14, 2006 10:32 pm

It could just need a base idle adjustment :?:

blackster · Postby **blackster** » Thu Dec 14, 2006 10:48 pm

Alf wrote:Not in mine in the last 58,000 km,

I'd suspect that either the battery is shot, not fully charged, or has a loose connection.

Mine's a daily driver, so the battery doesn't get too much of a chance to discharge, but if you're running an alarm and only drive it on weekends, for instance, there's a good chance the battery never gets fully charged.

Cheers,
Alf

Not sure how you are linking temporary idle dip with the battery when the car is running and the fan or powerwindows or high beam is operating. I have checked the connections they appear to be ok.

The battery is two years old, wouldnt you expect a longer life then that from a mx5 battery, if you reckon its related to the battery? The car does have an alarm, I drive it 4 days per week.

blackster · Postby **blackster** » Thu Dec 14, 2006 10:54 pm

Andrew wrote:It could just need a base idle adjustment

I was thinking that as well, daniel from mania adjusted it to sit at 800rpm, he commented that temporary idle dip is normal when the fan comes on.

Just wanting to clarify if other owners are getting this, as it appears to occur when you hold down power window button or hold the high beams.

timk · Postby **timk** » Thu Dec 14, 2006 11:12 pm

I get it slightly when the air con kicks in but not when winding down windows or turning on lights.

JBT · Postby **JBT** » Thu Dec 14, 2006 11:32 pm

So Saboteur, 2004 SE eh?

Tell me more. :mrgreen:

blackster · Postby **blackster** » Thu Dec 14, 2006 11:35 pm

saboteur wrote:I get it slightly when the air con kicks in but not when winding down windows or turning on lights.

Would you mind doing the following tests?

When the car is warm and at idle pull the power window button back whilst the window is up and see what happens to your idle. So your pressing the power window button to close the windows even though the windows are closed.

When the car is warm and at idle pull the latch for high beams back as if your flashing someone with the drive lights in the off position and see what happens to your idle.

Cheers

JBT · Postby **JBT** » Thu Dec 14, 2006 11:43 pm

The ECU should pick any electrical load changes quickly and correct the idle speed almost instantly so that any RPM change is almost imperceptible. I can hardly even detect the A/C kick in/out on our 02 Astina. It's very obvious with the 95 MX-5 though. However, there are no idle RPM changes evident with changes in electrical load.

Has your battery been recently disconnected? Has the car been recently serviced? What you're seeing is not normal IMHO. Sounds like a warranty job to me.

PT · Postby PT » Fri Dec 15, 2006 7:29 am

Welcome to the club sab

No idle dipping here.

Richee · Postby **Richee** » Fri Dec 15, 2006 7:52 am

saboteur wrote:I get it slightly when the air con kicks in but not when winding down windows or turning on lights.

EDIT Sorry I dont have SE but ...

I get an Idle dip when coming to a stop, but only sometimes and I cannot reporduce it. I have new top something leads ( one year ago ) and serviced 10,000 k so maybe a service may fix.

I will pay more attention and see if I can find the cause.

So Saboteur is it Silver from the Northside ??

Richard

blackster · Postby **blackster** » Fri Dec 15, 2006 8:55 am

Ive spoken with another mechanic who works 5s and has stated that the above is normal when a increased electrical load is going through the alternator the idle stepper kicks in to correct idle drop.

If SE owners would like to do the following, it should reproduce the same results.

When the car is warm and at idle pull the power window button back whilst the window is up and see what happens to your idle. So your pressing the power window button to close the windows even though the windows are closed.

When the car is warm and at idle pull the latch for high beams back as if your flashing someone with the drive lights in the off position and see what happens to your idle.

timk · Postby **timk** » Fri Dec 15, 2006 10:10 am

Thanks PT!

I tried the window trick (putting it up when it was already up) and it didn't change the revs at all. I haven't tried the high beam thing because I had someone in front of me and I didn't want to scare them!

Cheers

PT · Postby PT » Fri Dec 15, 2006 10:35 am

So tell us more about the car!

JBT · Postby **JBT** » Fri Dec 15, 2006 11:44 am

blackster wrote:Ive spoken with another mechanic who works 5s and has stated that the above is normal when a increased electrical load is going through the alternator the idle stepper kicks in to correct idle drop.

Idle droop/dip/drop is not normal on any MX-5. The process the mechanic stated happens instantly and you'd barely notice any movement of the tacho let alone hear/see/feel an idle change of 200 RPM.

You may have a sticking/slow system component or an electrical problem.