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Sideways is t'only way!
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Discussion Starter · #1 ·
Been out for a blast this morning and all of a sudden the "Heat" symbol has decided to appear on the dash.

Was flicking on and off for a bit then seemed to be on solid... but seemed to disappear if I put my foot down a little?

Should I be worried?

Should I do anything?

If I'm getting rid of the cat I assume this wouldn't be a problem then?!

Thanks
 

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Don't get too worked up. There is a slight chance you are running a little rich and may have legitimately overheated the cat, more likely it is just the sensor being a little finicky. They are know to come on with just a good hard thrashing. And when/if you remove the cat just unplug the sensor and leave it in the cat.
 

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Sideways is t'only way!
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Discussion Starter · #3 ·
I did think I might be running a little rich to be honest... sometimes it smells a little "petrolly" ?

I did also have a slight mis-fire a while ago which seems to have disappeared.

What could cause it to be running rich?

Just wondering what I should do to resolve the problem really.

I was planning on removing the cat anyway but if it's running rich then assume that needs sorting anyway?
 

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Sideways is t'only way!
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Discussion Starter · #5 ·
Mine did this a few months ago. I did get rid of the cat and havnt had it since. Did you engine cut out? I think mine may have done I cant remember.
Nope no cutting out.. car was running and pulling fine just the light on the dash.

I want to get rid of the cat really anyway.. am I right in saying you don't need the cat on imports for the MOT?
 

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Sideways is t'only way!
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Discussion Starter · #7 ·

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Sideways is t'only way!
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Discussion Starter · #8 ·
Well car has been parked up for about 4 or 5 hours and started it up and got the "Heat" symbol straight away... surely the cat couldn't be overheating after 4 or 5 hours sat there in the cold?

Thinkin for this reason the sensor might be dodgy? Or the cat knackered?

On the drive home (couple of miles) the light was flicking on and off.. didn't seem to be linked to anything in particular?

Any ideas? Just bothered about driving it in case there's something wrong I should be looking at??
 

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i think its telling you the cats on its way out.

never thought of it as mixture related. If i did, i would think it lean. Odd that
 

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Sideways is t'only way!
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Discussion Starter · #10 ·
Hmmm.... maybe could be on its way out.

Will pickup a de-cat anyway... was just wondering if there's anything else I need to check.

If it's running lean maybe what could be causing this or way to check?
 

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Happily expanding the To Do list since 1997
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The "HEAT" sensor is supposed to tell you the cat's overheating. The usual reason for that would be unburnt fuel reaching the cat, which hints at a misfire.

The problem with the sensors fitted to Roadsters is that typically they never come on at all until one day they break down and come on permanently.

So this may be telling you that you have a misfire (time for new plug leads, maybe) or it could just be a spontaneous failure of the sensor.

If the light comes on permanently, then the simplest way to put it out is to unplug the sensor (no need to remove it from the cat - there's a connector in the cable about a foot away from where it plugs into the side of the cat). If you unplug it, the light will stay out.

If you're worried about the cat itself, I wouldn't be. My original cat soldiered on for years after my Heat lamp came on. Didn't affect its emissions results at all.
 

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Sideways is t'only way!
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Discussion Starter · #12 ·
I'm not really worried about the cat... if the cat is knackered then i'll just get a de-cat as I was planning on de-catting it anyway.

More bothered about if I do have a mis-fire as you suggest and if that's spewing unburnt fuel out.

I did have a proper mis-fire a while ago when the car wasn't used for a few weeks however after a days use it seemed to clear... it seems to rev up fine and doesn't appear to be mis-firing? I assume that it could be a slight mis-fire that isn't obvious?

Don't really want to just unplug the sensor... as I'm sure it's not there for nothing? Unless of course the sensor is bust...

So maybe the plan is check to see if I have a mis-fire? (how do I do this myself... or should I go to the garage)
Replace leads anyway?
Fit de-cat? (what happens with the sensors then by the way)
Replace sensor? (if so what do I need)
 

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Happily expanding the To Do list since 1997
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I'm not really worried about the cat... if the cat is knackered then i'll just get a de-cat as I was planning on de-catting it anyway.

More bothered about if I do have a mis-fire as you suggest and if that's spewing unburnt fuel out.

I did have a proper mis-fire a while ago when the car wasn't used for a few weeks however after a days use it seemed to clear... it seems to rev up fine and doesn't appear to be mis-firing? I assume that it could be a slight mis-fire that isn't obvious?

Don't really want to just unplug the sensor... as I'm sure it's not there for nothing? Unless of course the sensor is bust...

So maybe the plan is check to see if I have a mis-fire? (how do I do this myself... or should I go to the garage)
Replace leads anyway?
Fit de-cat? (what happens with the sensors then by the way)
Replace sensor? (if so what do I need)
A slight misfire would be hard to spot, even if you keep careful track of your mpg. You might start hearing interference on the radio if it begins to get worse. You could just leave it and see if anything develops, or it might be worth investing in a new set of plug leads anyway to see if you can feel the difference. Even if it doesn't make any improvement, you can always keep the old ones as spares.

If the lamp is coming on when you start up from cold then the sensor is definitely borked. It shouldn't do anything till it reaches many hundreds of degrees C.

There is no harm in unplugging the sensor; lighting that lamp on the dash is literally all it does. It's not connected to the ECU or any other system in the car. Only Japanese models have them fitted anyway (I guess they must have been a statutory requirement in Japan). Mazda didn't bother fitting them to MX-5s for any other world market.

Since the sensor is built into the cat, if you decat you remove the sensor. Nobody in the UK stocks the sensor (AFAIK). I only once heard of someone who got their broken sensor replaced. The garage who did it ordered the part from Japan at not inconsiderable expense and I can't help thinking they rather took advantage of their customer's lack of knowledge to do unnecessary work.
 

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Sideways is t'only way!
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I think my only concern is weather the car is still fine to drive and give some stick until I can get a de-cat and or new leads etc?

This is kinda my daily... I do have access to another car for 3 days of the week and technically don't "need" the car to get to work but it's handy... and the weather is getting nicer so I enjoy the commute
 

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Sideways is t'only way!
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Its fine
Go forth and drive!

Does that help?
Oh you've decided to grace us with your presence... it does help slightly... however.

I think I might have solved the mystery of the heat symbol possibly.

Was driving along today minding my own business and thought "what the hell is that new grating noise?"

Anyway a quick glance under the car and there's some random wire dragging along the floor... not sure what it's for but I'd hazard a guess at something to do with the heat symbol?

Here's some pics....

This is where it was dragging on the floor...



This is the top of it ?



This is where I /think/ the wire has snapped from?





Any ideas?
 

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Sideways is t'only way!
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Discussion Starter · #19 ·
Any ideas?
Yes, that is the cat overheat sensor. Disconnect it at the connector near the PPF now and forget about it.
[/quote]

PPF?
 

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