On Sun, 30 Jan 2005 14:06:23 -0600, TCS
> wrote:

>There should NOT be zillions of vacuum lines unless somehow mazda slipped
>you an engine from the late 70's.
>
>There should be less than a half dozen actuall vacuum lines. Stuff like the
>brake power unit, the idle air manifold, and the cruise control actuator.
>Start at the intake manifold and look for stuff coming off it.

================
Well, I'm kind of an old-timer. More than one going to the
distributor (and in the really old days, one going to the wipers) kind
of throws me.
================

>Does the ECU report any errors?

================
No errors show on the dash, but I don't think it is equipped to do
that. Doesn't seem to have a "Check Engine" light or whatever.

Is there a port to plug into with a relatively affordable unit to read
out such codes? I could use a hint like that.
===============


Is your ignition system perfect -- nice fat
>spark if you pull a wire and hold it 1/4-1/3" from a ground? Timing correct?


==============
Timing is dead-on. Plugs are new within three months. Cap and rotor
new. Wires could be questionable. Filters are good. Haven't checked
spark, but will on Saturday, if the weather is bearable.
=============

>
>Don't replace anything unless you've actually tested it bad. One mistake will
>easily cost you more than having a mechanic diagnose the problem.

============
I only meant that, if this is a textbook case of the symptoms of some
particular failed control, part that I would be willing to roll the
dice. No, I don't want to go replacing bushels of parts on a whim.

PLEASE NOTE that the idle only goes silly when the car is in DRIVE.
Not Park, not neutral, and not even when it is in REVERSE. This seems
kind of odd to me.

Thanks for any help you can offer,

Hamish

Original Post Below:

>On Sun, 30 Jan 2005 11:46:15 -0500, Hamish WAUGH > wrote:
>>Here is the problem.
>
>>'91 Mazda 626 2.2 without turbo (Yeah, I wish.) has a rolling miss at
>>idle when in gear. It runs and idles smoothly at all other times, but
>>if the car is fully warmed up and I stop at a traffic light, it will
>>idle smoothly for about four or five seconds, then the idle will drop
>>and surge, drop and surge, from almost stalled to normal. If I put it
>>back into gear it will go right to normal (750 rpm) and stay there.
>
>>I have looked for a vacuum leak, but there could still be one that I
>>missed. (Zillions of hoses.) I know that it could be just about