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Discussion Starter #1
So I'm still sorting out my GTV6, and I took it for a relatively long drive this weekend. While on the freeway, I didn't shift out of fourth for several miles.. at about 70mph. And then the "exh temp" light came on.

I shifted into fifth, and the light went out after about 5 minutes or so.

So where is the sensor? And what is it's parameters?

Apparently cruising in fourth causes too much heat in the cats?

Thanks.

-Russell
 

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if anybody has info on this thing, id also like to know.

In my car, it seems to work fine (lights up for a second at start), but ive yet to get it to light. I have driven this thing reeeally hard too. The Coquihalla highway nearby is 45 Km of strait 8.5% grade, and I was motoring up it fast as she would go on a 90F day, and nothing lit.

its not really useful I guess anyhow, as im sure after 28 years there's probably nothing left of the cat anyways
 

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So I'm still sorting out my GTV6, and I took it for a relatively long drive this weekend. While on the freeway, I didn't shift out of fourth for several miles.. at about 70mph. And then the "exh temp" light came on.

I shifted into fifth, and the light went out after about 5 minutes or so.

So where is the sensor? And what is it's parameters?

Apparently cruising in fourth causes too much heat in the cats?

Thanks.

-Russell
When running at WOT, the tps puts the injection system into open-loop and dumps extra fuel in. Maybe running that way for a while allowed excess fuel to overheat your cat, triggering the warning. Upshifting probably brought the TPS back into closed loop.

Bill
 

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Discussion Starter #4
Well, I wasn't at FULL throttle. In fact, I was probably only 200 rpm over what I'd normally be at. Which surprises me that anything would be different.

My car just passed smog, so I'm guessing there are no gross problems with my fuel system. But having a temp sensor go off means that the temp was higher. Which it should be because I was driving at a higher rpm. But how sensitive is that sensor? Where is it? And what temp is considered too high?
 

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Well, I wasn't at FULL throttle. In fact, I was probably only 200 rpm over what I'd normally be at. Which surprises me that anything would be different.

My car just passed smog, so I'm guessing there are no gross problems with my fuel system. But having a temp sensor go off means that the temp was higher. Which it should be because I was driving at a higher rpm. But how sensitive is that sensor? Where is it? And what temp is considered too high?
IIRC, Greg's site says the TPS should be set to signal full throttle at 60% open. I have no idea what rpm and what throttle position doing 70 in 4th means for your particular car, since I don't know what T/A and final drive you're running, or how your tps is set.
 

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Discussion Starter #6
Hmm.. now that you mention it, perhaps that is THE PROBLEM!

Perhaps my TPS isn't adjusted right. Although, I am sure I looked at it, and it didn't seem that off. Even at 70 in fourth, you aren't using that much throttle. Like I said, it's only a few hundred rpm more than fifth..but if the TPS was misbehaving, and dumping gas it would be really hot down there!

Thanks, I'll go and check that out.
 

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...But how sensitive is that sensor? Where is it? And what temp is considered too high?
the sensor is located on the passenger side exhaust runner before the catalytic converter. the wires are of two types of metals, which suggests that its a "K" type thermocouple. other than that, I know nothing about its trigger temperature, or what is even considered too high a temp on this engine. I know on many turbo engines, 900°C is considered about MAX before meltdown. The alfa V6, im clueless of its normal EGT

...however since the sensor is likely k-thermocouple, its likely any EGT gauge could be used with this sensor to measure exhaust temperatures.
 

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I have been going through my manual since I'm still learning my car. The Exh. Temp warning light should come on an stay on a couple seconds (as do the Fasten Seat Belts and Brake warning light) - these flashing on all indicate the devices are working properly. The Exh Temp light is the catalyst over temperature warning light - if this comes on while driving let up on the accelerator pedal. If it stays permanently lit - you may need engine maintenance.

I found a lot of the info on page 12 of my 1979 Spider manual.
 

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you may pass emissions, but you may be running lean. really need a wideband O2 sensor and monitor while on a dyno to do a real engine check
 

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Mine has always been unreliable. It sometimes comes on and stays on right after I start the car and I have never gotten a good sense that it is really accurate to any certain temp!

Lots of other folk just remove the light. I personally enjoy the red glow from time to time! Not quite as good as the Milano's "red alert"..
 
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