various problems with my MX

Hi folks
I've been a very happy owner of my Miata/MX5 for over a year now, but
it has recently been causing me some problems, and I am after some
advice/help.

My car is a 1991 model 1.6i

Problems a
1) Car overheats very easily (even just city speeds of 30mph or so).
Gets to a point where the water in the coolant reservoir starts to
bubble. Took my car into its 117k service, and they could find nothing
wrong with it. What could be wrong?

2) Low miles per gallon. This is down to the oxygen sensor not being
connected to anything I think! There does not seem to be any sort of
wire connected to the oxygen sesnor. If I was to put attach a wire,
where does the other end join on to?

3) A Metallic sort of buzz seems to appear when I am in fourth gear
(2000 rpm - 3000rpm). Noise seems to come from CAT area? Is this
fixable? Is this connected to the problems I have read about elsewhere?

4) My air compressor does not work, and since I have owned this car,
there has never been a belt around the pully. Subsequently the pulley
rattles all the time when in low gears and drives me mad. Can I safely
put a belt arouund it? or just tape it up, so it doesn't rattle?


Sorry for the list of questions, but my local Mazda dealer stung me
recently for lots of money and didn't fix any of my problems at all. So
I was thinking that any advice you give me hear, I can go to a local
garage and get them to fix these things for me.
Any advice is appreciated.

Regards
Alan

Problem #1 doesn't sound good. The 1st thing that comes to mind with air
bubbles in the overflow might be a bad head gasket, but don't quote me on
that since these radiators cane become plugged easy. A trip to a quality
radiator shop should get you a correct answer.

Problem #2 with low gas mileage is no doubt due to the lack of an O2 sensor.
When the sensor is bad the cars computer goes into a closed loop, just like
before the coolant comes up to operating temp and the car will run in a rich
state. It should only run rich when it's cold and above 4 or 5k rpm's. This
condition will ruin the catalytic converter eventually.

Problem #3 is an easy one. The heat shield around your Cat and pipe ahead of
is rotted and rattling. This can be fixed by hose clamps sometimes or by
removing the heat shield. Midas put a new clamp around the shield on the
forward pipe and removed the cat shield for free for me once. I understand
that some cat replacements come without a shield.

Not sure about problem #4, but it can't be helping the emissions by missing.
I don't even recall something like this on my 91A and would have thought
that more stuff would have run off the same belt.

Good luck and keep us updated.


"nytrex" > wrote in message
oups.com...
> Hi folks
> I've been a very happy owner of my Miata/MX5 for over a year now, but
> it has recently been causing me some problems, and I am after some
> advice/help.
>
> My car is a 1991 model 1.6i
>
> Problems a
> 1) Car overheats very easily (even just city speeds of 30mph or so).
> Gets to a point where the water in the coolant reservoir starts to
> bubble. Took my car into its 117k service, and they could find nothing
> wrong with it. What could be wrong?
>
> 2) Low miles per gallon. This is down to the oxygen sensor not being
> connected to anything I think! There does not seem to be any sort of
> wire connected to the oxygen sesnor. If I was to put attach a wire,
> where does the other end join on to?
>
> 3) A Metallic sort of buzz seems to appear when I am in fourth gear
> (2000 rpm - 3000rpm). Noise seems to come from CAT area? Is this
> fixable? Is this connected to the problems I have read about elsewhere?
>
> 4) My air compressor does not work, and since I have owned this car,
> there has never been a belt around the pully. Subsequently the pulley
> rattles all the time when in low gears and drives me mad. Can I safely
> put a belt arouund it? or just tape it up, so it doesn't rattle?
>
>
> Sorry for the list of questions, but my local Mazda dealer stung me
> recently for lots of money and didn't fix any of my problems at all. So
> I was thinking that any advice you give me hear, I can go to a local
> garage and get them to fix these things for me.
> Any advice is appreciated.
>
> Regards
> Alan
>

Here is a good thread on Miata.net. I hadn't thought about the cooling fans
and the radiator cap either.
http://forum.miata.net/ubb/ultimateb...c;f=5;t=038996


"nytrex" > wrote in message
oups.com...
> Hi folks
> I've been a very happy owner of my Miata/MX5 for over a year now, but
> it has recently been causing me some problems, and I am after some
> advice/help.
>
> My car is a 1991 model 1.6i
>
> Problems a
> 1) Car overheats very easily (even just city speeds of 30mph or so).
> Gets to a point where the water in the coolant reservoir starts to
> bubble. Took my car into its 117k service, and they could find nothing
> wrong with it. What could be wrong?
>
> 2) Low miles per gallon. This is down to the oxygen sensor not being
> connected to anything I think! There does not seem to be any sort of
> wire connected to the oxygen sesnor. If I was to put attach a wire,
> where does the other end join on to?
>
> 3) A Metallic sort of buzz seems to appear when I am in fourth gear
> (2000 rpm - 3000rpm). Noise seems to come from CAT area? Is this
> fixable? Is this connected to the problems I have read about elsewhere?
>
> 4) My air compressor does not work, and since I have owned this car,
> there has never been a belt around the pully. Subsequently the pulley
> rattles all the time when in low gears and drives me mad. Can I safely
> put a belt arouund it? or just tape it up, so it doesn't rattle?
>
>
> Sorry for the list of questions, but my local Mazda dealer stung me
> recently for lots of money and didn't fix any of my problems at all. So
> I was thinking that any advice you give me hear, I can go to a local
> garage and get them to fix these things for me.
> Any advice is appreciated.
>
> Regards
> Alan
>

"Mike" > wrote in message
...
> Here is a good thread on Miata.net. I hadn't thought about the cooling
> fans and the radiator cap either.
> http://forum.miata.net/ubb/ultimateb...c;f=5;t=038996
>

About a year ago I had an overheating problem and found the temp sensor at
the front of the engine cracked. It was hard to find since it looked
normal. I finally found it when I tried to take it out to replace it and it
fell apart in my hands. As noted, without the temp reading the engine
control computer thinks the engine is cold. The result is that the fans
don't turn on leading to over heating at slow speeds and the engine runs
rich leading to low gas mileage. I am real suprised that a dealer wouldn't
find this, so may the problem is something else.

Gus (91 BRG)

#1 - It could also be a bad thermostat. This will show up if the car is
run hard which may be the case due to the other problems.

#3 - Could be the cat failing which could also cause #2. I had similar
noise form mine and it was shot.

Sounds like someone may have really messed with the emissions systems
and caused a number of other problems.

glen
'91 miata

"nytrex" > wrote in message
oups.com...
> Hi folks
> I've been a very happy owner of my Miata/MX5 for over a year now, but
> it has recently been causing me some problems, and I am after some
> advice/help.
>
> My car is a 1991 model 1.6i
>
> Problems a
> 1) Car overheats very easily (even just city speeds of 30mph or so).
> Gets to a point where the water in the coolant reservoir starts to
> bubble. Took my car into its 117k service, and they could find nothing
> wrong with it. What could be wrong?
>
> 2) Low miles per gallon. This is down to the oxygen sensor not being
> connected to anything I think! There does not seem to be any sort of
> wire connected to the oxygen sesnor. If I was to put attach a wire,
> where does the other end join on to?
>
> 3) A Metallic sort of buzz seems to appear when I am in fourth gear
> (2000 rpm - 3000rpm). Noise seems to come from CAT area? Is this
> fixable? Is this connected to the problems I have read about
elsewhere?
>
> 4) My air compressor does not work, and since I have owned this car,
> there has never been a belt around the pully. Subsequently the pulley
> rattles all the time when in low gears and drives me mad. Can I safely
> put a belt arouund it? or just tape it up, so it doesn't rattle?
>

"Glen Thompson" > wrote in message news:<Ze0Hd.21237$EG1.7451@lakeread04>...
> #1 - It could also be a bad thermostat. This will show up if the car is
> run hard which may be the case due to the other problems.
>
> #3 - Could be the cat failing which could also cause #2. I had similar
> noise form mine and it was shot.
>
> Sounds like someone may have really messed with the emissions systems
> and caused a number of other problems.
>
> glen
> '91 miata
>
Just to let you all know. My car is now back on the road again. :-)

1. Overheating was down to a knackered thermostat. New one installed
and no problems since. Although, it did start to overheat on my first
journey for about 5 mins, and then setteled down again, and no
problems since (about 300 miles later).

2. Oxygen sensor installed, and has now almost increased by MPG by
50%. Instead of 21 MPG, now getting about 30! Just think how much this
has cost me in fuel over the last 12 months.

3. Metallic Buzzing Not fixed. Garage seem to think its the baffler in
the rear of the exhaust, but I'm not so sure. If I do get a new rear
exhaust, what's all this about Back-Cat's? and do they give more
oomph? And how much? My car is just a lowly 1.6? Is it really worth
it?


4. Second hand compressor costs about £300 so have left if for just
now, until I'm a bit more flush.

However, just after getting this all fixed, my water pump in my car
exploded and had to get a costly fix to it and the gaskets / seals.
What a joyous month January has been.


Thanks for all your help and advice.

Alan

In article >,
(nx) wrote:

> 3. Metallic Buzzing Not fixed. Garage seem to think its the baffler in
> the rear of the exhaust, but I'm not so sure.

It's usually the heat shield on the downpipe, between the header and the
catalytic conver. It cracks, or a spot weld breaks, and it buzzes around
3000 rpm. Tightening a stainless steel hose clamp around the upper end
of the shield usually cures the buzz.

OTOH, in my case it was the cat going bad.

--
Lanny Chambers, St. Louis, USA
'94C
the alignment page:
http://www.hummingbirds.net/alignment.html