In article >,
(William R. Watt) wrote:

> A hand held vaccum guage can tell if there is possible a gasket leak. I'd
> plug mine in and rev the engine at idle. I suppose a dash-mounted vacuum
> guage might show something when the problem actually occurs. There's a
> guide to diagnosing engine problems with a vacuum guage on my website (see
> below) under "Cars".

I'll take a look at that and see if it'll help at all.

> I have a Chilton import car manual for 1983-90 but it doesn't show if the
> 626 has transistorized points in the distributor.

I'm using the factory service manual for this beast. It's an '82.

'83 model year was the first substantial change to the 626 since 1978.
Quite similar to an '82 engine, but "similar" isn't "same". Dunno exact
details on the differences besides "It's crosswise".

Yes, mine uses the "breakerless points" - Mazda calls the module the
"ignitor" - A hall sensor, or similar type of "Hey, stupid! It's time to
fire the coil!" rig. That unit lives under the rotor in the distributor,
and is the only thing electronic on this engine. And boy, do I hope it
isn't going bad, since trying to replace it looks to be a project that
ranks right up there with finding hens' teeth. The actual replacement
ain't so bad, but first you have to find a replacement module, and good
luck doing that...

> When that starts to go
> you can get intermittent timing problems but I can't imagine how it can
> cause such delayed ignition after the ignition is turned off. Some auto
> parts stores will test the ignition module for free. I've had one off an
> '89 Fesitva (Ford/Mazda) tested. The printout test for low and high speed
> conditions so they differ somehow.
>
> As for possible emisson control problems, I don't know what the 82 Mazda
> has on it but a Haynes emission control book says the following in the
> troubleshooting section:
>
> Hesitation or stumble on acceleration:
> - defective acclerator pump in carburettor

No evidence for this one. Acc. pump dumps what looks to be real close to
the specified amount of gas down the bore when the pedal is mashed. I'd
have to try (and it'll be an interesting task...) to catch the fuel
charge to see how close the amount actually is, but it appears to be
about right.

> - defective throttle position sensor or circuit

As mentioned above, only eletronics on this engine is the "breakerless
points" module in the distributor. Not counting my MP3-capable CD
player, the digital clock in the dash contains more
electronics/computing power than all the rest of the car combined.

> - defective air temperature sensor or circuit

Nonexistent on this engine.

> - defective MAP (mass air pressure?) sensor or circuit

Same as above.

> - ignition timing

Doesn't APPEAR to be a problem, at least when checked as per book specs.
May "go bad" as revs/load increases, but I haven't got a way to test
that, since I've never managed to get the problem to happen without the
speedo reading 35+, and I can't run that fast and hold a timing light at
the same time

> - trottle bore or plate

Pray elucidate? I'm assuming that means "throttle bore or plate
dirty/damaged"? If so, I think that idea can be written off. Both are
"squeaky-clean", and neither shows any visible damage.

> Backfiring:
> - vacuum leak in PCV or canister purge line

Couldn't find any vacuum leaks when I did the unlit propane torch test
yesterday.

> - defective air injection valve
Possible - I'll test that come daylight. But backfire isn't the main
problem - The little bit of backfire I get get seems to be more of a
secondary symptom. If that valve is defective, I'd expect MAJOR
(Gunshot-style) backfiring anytime I get off the gas - Which was exactly
what I had when the vac. line controlling the injection valve was
cracked, leaving the valve effectively non-functional. I have no such
trouble currently - The little bit of backfire I get is a barely-audible
"pop-pop-poppety-pop" type thing - When it happens at all, that is...

> - ignition timing
Again, doesn't appear to be a problem.

>
> Engine diesels (runs on) when shut off or dies too fast:

This isn't an issue - or at least, I don't think it is... Except for the
occasional delayed "pop" out the tailpipe a few seconds after the engine
stops spinning, shutdown is 100% normal.

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