ChrisSF
ChrisSF
10/6/11 9:08 a.m.

We just bought a 1990 mazda miata and plan to upgrade when funds are available. In the meantime, the car runs great. I'm having one issue... when I come out of gear to stop/idle the car wants to shut off. Otherwise the car idles fine at 750. Anyone have an idea of what it might be? New plugs, new wires, new air filter have been installed.

RossD
RossD SuperDork
10/6/11 9:16 a.m.

Did you buy good plugs and wires?

ChrisSF
ChrisSF New Reader
10/6/11 9:21 a.m.

I did.

EvanB
EvanB SuperDork
10/6/11 9:29 a.m.

It is a common problem. You need to jump 2 terminals in the diagnostic box (10 and ground I think) and adjust the idle with the screw on the throttle body under a cap.

There should be a write up on Miata.net under "idle droop".

EvanB
EvanB SuperDork
10/6/11 9:34 a.m.

At least that worked for me on my 91, searching Miata.net now there are a few solutions from adjusting the idle to cleaning the throttle body.

noodle
noodle New Reader
10/6/11 10:05 a.m.

Common for the 90...buy a new dashpot. It's the little mushroom looking dillybob that sits on the side of the throttle body

foxtrapper
foxtrapper SuperDork
10/6/11 10:05 a.m.

Same with my Miata, and many other cars other than Miatas. Folks will just twirl anything they find that might increase idle speed, causing entertaining problems.

Keith
Keith SuperDork
10/6/11 10:13 a.m.

Definitely check the idle speed. It's been a well-documented problem on Miatas for a couple of decades now. It's an easy fix.

Javelin
Javelin SuperDork
10/6/11 10:49 a.m.

Idle speed, clean the throttle body, dashpot, and adjust the timing (in that order). My 93 needed all 4 before it idled great.

TenaciousD
TenaciousD New Reader
10/6/11 5:46 p.m.

The usual fix is to set the "base" idle. That is the idle that occurs when the computer is not intervening and setting it. The pins in the diagnostic connector that you need to jump are TEN and GND. TEN stands for "Test ENgine", not the number 10. Use a paper clip to jump the terminals and then set the idle to ~800. Check the timing while you're at it.

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