Miata Mailing List: November 1998, Message #797

sponsored by

>From: "John Byrns" <jbyrns@hoflink.com>
>Subject: idle hunt
>Date: Tue, 10 Nov 1998 09:47:06 +0000
>
>Early last week I drained my battery, and got a jump start.
>
>Ever since that day, I have been having an Idle hunt problem.
>
>Most of the time that I bring the car up to 4,000 rpms, and then
>get off the gas, the engine decelerates rapidly down to 200 rpms,
>bounces up to 1,200 rpms, does this for about 2 to 3 times, then stops   
at
>850 rpms and sits there rock solid.
>
>Sometimes I will bring the rpms up to 4,000 and get off the gas, and
>the idle will fall slowly to 850 rpms and sit there like a rock.
>
>The engine has only stalled once, and that was when I was under the   
hood,
>playing with the throttle trying to cause it to stall.  I would jerk the
>throttle
>repeatedly and if I do it enough I can stall the engine.  It sounds like   
the
>engine
>is running to lean when it does go down to 200 rpms.
>
>I checked the error codes and did not have a single error.
>
>I drove the car on a 12 hour round trip this weekend hoping it would   
clear
>it self up, and I did not.  On the trip I was doing 90+mph most of the   
way
>and still was getting over 30 mpg.
>
>Any suggestions,
>91 A package
>57,500 miles -  no repairs except for a blown clutch (I drive it hard)
>I did put in new spark plugs and  PCV Valve only a few weeks ago.   
 Ignition
>wires
>were changed at 25,000 miles.  Jackson Racing CAI was added this summer.
>
>-------
>John Byrns
>jbyrns@hoflink.com
>

John,

Try trickle charging your battery. (at 2 Amps or less)

The idle hunt can be caused by many things, low battery being one of   
them.

The Miata's battery is a strange beast, and doesnt take to fast charging   
very well. Even though you've driven around a lot since the battery   
flattened episode, the cars altenator charging system is essentially a   
fast charge, and this just heats the battery up, making it accept less   
charge....  So basically, your battery whilst being recharged enough to   
start the car, has probably never regained full health....

A slow charge overnight should fix it....

Good Luck,

Fletch.

P.S.  More about the Miata's quirky battery, and its charging   
requirements can be read in the Tech section of Miata.net