Idle

warrior · Post by **warrior** » Thu Jan 23, 2014 5:53 pm

My wifes mx5 does not idle like my car when cold. My car revs a big higher until it is warm then drops back.

Hers idles when cold about the same rpm as when warm. It is not a big issue but it is a bit annoying.

Any ideas where to look to fit this?

SLYDIT · Post by **SLYDIT** » Thu Jan 23, 2014 7:10 pm

clean your throttle body and idle speed solenoid valve and then reset your idle speed

Post by **jif** » Fri Jan 24, 2014 9:35 am

I'd think as long as its not stalling its not practically a big deal. The higher revs are mostly to heat up the engine and catalyst faster. ie economy/emissions related.

If your car is a Toyota, they seem to be programmed to idle crazy high (4a-ge ... nearly 2k rpm!) when cold.

On 23 January 2014 19:10, SLYDIT <mx5talk@mx5forum.co.nz (mx5talk@mx5forum.co.nz)> wrote:

clean your throttle body and idle speed solenoid valve and then reset your idle speed

------------------------
RED '90 TURBO.
SCARING PRIUS DRIVERS SINCE 2002
http://www.cardomain.com/ride/264041/19 ... -5/page-6/

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4A-GE · Post by **4A-GE** » Fri Jan 24, 2014 9:49 am

My blacktop idled at about 1300 on real cold days.
The 4A-F in my AE92 didn't know what a cold idle was, and probably didn't care either. 850rpm all day erryday. Kinda miss that car, made such a cool noise on startup...

warrior · Post by **warrior** » Fri Jan 24, 2014 12:34 pm

It has a 4 wire heated ox sensor so that may have something to do with it?

marcellarius · Post by **marcellarius** » Fri Jan 24, 2014 3:45 pm

It's unlikely to be the O2 sensor. The O2 sensor controls fuel mixture in order to keep the catalytic converter working efficiently but it takes a while to heat up so the ECU will ignore it and use open-loop fuel control until the engine has warmed up. The heater mainly helps get the O2 sensor up to temp faster for emissions regulations.

I'd look at the idle speed control and air bypass, as SLYDIT suggested. A stop-gap measure would be to open the idle adjustment screw slightly more (this sets the minimum airflow past the throttle plate) but a dirty/faulty idle speed control is likely the problem.

This article on Miata.net describes diagnosing problems with the ISC system on a 1.6. The 1.8s use a different intake/throttle design.

http://www.miata.net/garage/isc.html

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