Newbie needs help: Miata Backfires During Shift?
DLynch
has an aftermarket stainless steel muffler, I guess low restriction (the
previous owner installed it).
I've changed the plugs and plug wires using dielectric grease on the plug
boots and never-seize on the plugs.
I've run out of ideas and need help!
Thanks in advance,
Dave
London, Canada
'92 black/tan
pochas
<dly...@attcanada.net> wrote:
Before you do anything else, run a tank of gas with a bottle of injector
cleaner, such as Chevron "Techron." The computer is supposed to shut off
the injectors when you take your foot off the gas. If the injectors are
sticking or leaking, they don't shut off, causing the backfiring. Also,
stay away from off-brand gasoline.
Charles P. '90 Mariner Blue, Sebring
Leon van Dommelen
>Our '92 Miata backfires when I shift. What should I look for to fix it?
If you did not recently, replace your air filter. It is a common
symptom of a dirty filter (making the mixture too rich.) Cleaning
my air filter helped me greatly after driving the dust clouds
of the Alaska Hwy. Though I still have a bit of backfire left.
I am planning to try Techron injector cleaner as suggested by Charles
next. No, you DO NOT stay away from off-brand gas while driving
the Alcan or Cassiar. Do you know how long a walk it is to
the next gas station? You just hope the stuff has enough oil in
it to burn.
> It
>has an aftermarket stainless steel muffler, I guess low restriction (the
>previous owner installed it).
>I've changed the plugs and plug wires using dielectric grease on the plug
>boots and never-seize on the plugs.
>I've run out of ideas and need help!
>Thanks in advance,
>Dave
>London, Canada
>'92 black/tan
Leon
--
Leon van Dommelen, Human Bozo, the dented 96 Sebring Miata
------------------- Have Miata, wish I could travel -----------------
REMOVE THE "z"s -> domm...@zmiata.net www.eng.fsu.edu/~dommelen
mj...@my-deja.com
loud bang that sounds like a gunshot. When you upshift, your engine
turns into an air pump briefly, and you tend to get a mixture of
unburned fuel and air showing up in the muffler. The stanless muffler
tends to result in a few hotspots (a characteristic of stanless steel,
but its essentially harmless.) I kinda like it....its like an old MG, if
it isn't too loud, I wouldn't worry about it...if its a LOUD bang that
reverberates through the car...you may have problems. BTW teh Miata has
a mass-airflow system, I think its capable of compensating for a dirty
filter, you lose power but it does not run rich.
Mark
In article <37b98a53...@nntp.ix.netcom.com>,
Sent via Deja.com http://www.deja.com/
Share what you know. Learn what you don't.
Leon van Dommelen
>You need to differentiate backfire from a bit of over-run. Backfire is a
>loud bang that sounds like a gunshot. When you upshift, your engine
>turns into an air pump briefly, and you tend to get a mixture of
>unburned fuel and air showing up in the muffler. The stanless muffler
>tends to result in a few hotspots (a characteristic of stanless steel,
>but its essentially harmless.)
Thanks. I was worrying my valves might be burning up. Glad it is
probably my new exhaust. :)
> I kinda like it....its like an old MG, if
>it isn't too loud, I wouldn't worry about it...if its a LOUD bang that
>reverberates through the car...you may have problems. BTW teh Miata has
>a mass-airflow system, I think its capable of compensating for a dirty
>filter, you lose power but it does not run rich.
My 1995 Mazda Miata Workshop Manual has under "Runs rough on deceleration/
Afterburn": "Troubleshooting Hints: 1 Airfuel mixture to rich" (with
no other hints), and the additional information "(a) Air cleaner element
clogged; (b) Fuel injection malfunction; (c) Fuel injector fuel leakage; (d)
Ignition timing maladjustment."
I know mine ran really rough before my air filter cleanings, not
just showing a lack of power. I guess the oxygen sensor only works
well for seady conditions. But even then, my J&S sensor shows its
rading to fluctuate quite wildly.
mj...@my-deja.com
DISGUSTING before its beyond the range that can be handled by the
electronics, if the throttle position sensor, rpm and mass airflow
sensor all sense reading that are out of whack (i.e with a VERY clogged
filter) the computer will probably go with a default setting which is
not ideal...like I said, it would have to be VERY clogged.
Mark
> My 1995 Mazda Miata Workshop Manual has under "Runs rough on
deceleration/
> Afterburn": "Troubleshooting Hints: 1 Airfuel mixture to rich" (with
> no other hints), and the additional information "(a) Air cleaner
element
> clogged; (b) Fuel injection malfunction; (c) Fuel injector fuel
leakage; (d)
> Ignition timing maladjustment."
>
> I know mine ran really rough before my air filter cleanings, not
> just showing a lack of power. I guess the oxygen sensor only works
> well for seady conditions. But even then, my J&S sensor shows its
> rading to fluctuate quite wildly.
>
> Leon
> --
> Leon van Dommelen, Human Bozo, the dented 96 Sebring Miata
> ------------------- Have Miata, wish I could travel -----------------
> REMOVE THE "z"s -> domm...@zmiata.net www.eng.fsu.edu/~dommelen
>
>
Leon van Dommelen
>The air/fuel mixture CAN go rich, but your filter would have to be
>DISGUSTING before its beyond the range that can be handled by the
>electronics, if the throttle position sensor, rpm and mass airflow
>sensor all sense reading that are out of whack (i.e with a VERY clogged
>filter) the computer will probably go with a default setting which is
>not ideal...like I said, it would have to be VERY clogged.
The J&S sensor shows that the mixture is constantly fluctuating between
very rich to very lean even under steady state idle or cruise conditions.
(This is standard behavior according to the J&S docs.) Hence, even under
such simple conditions, the oxygen sensor does not manage to keep
the mixture even close to the stochiometric ratio. It makes me wonder
what happens during unsteady conditions, especially if the airflow is
not as much as the controlling program expects.
Shaine
I believe i had a similar problem on my '94 mx6. maybe someone can clarify? ok,
it's an automatic. when accelerating from a full stop, it "jerks" on the first
shift, sometimes the second. also, it sometimes jerks right after i release the
acc. pedal. Other times, when it doesn't jerk, i hear a click of sorts, as if
it's trying to grab onto something? I had the transmission replaced, and it
lessened the impact, but it still does it somewhat regularly.
Any help would be REALLY appreciated.
Thanks in advance,
-shaine
Rexven
>Hey,
>
>I believe i had a similar problem on my '94 mx6. maybe someone can clarify? ok,
>it's an automatic. when accelerating from a full stop, it "jerks" on the first
>shift, sometimes the second. also, it sometimes jerks right after i release the
>acc. pedal. Other times, when it doesn't jerk, i hear a click of sorts, as if
>it's trying to grab onto something? I had the transmission replaced, and it
>lessened the impact, but it still does it somewhat regularly.
That is often a symptom of bad motor mounts. The motor shifts around
on the vehicle and it in turn affects the driveline. I had the same
thing happening on my Jeep (only 30k miles at the time.. Go figure?)
and swapping the motor mounts cured it completely.
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