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Discussion Starter #1 (Edited)
Just got my converters replaced and exhaust done to find out that the old converters werent just clogged, they had encountered a full thermal meltdown. I was told that this was caused by a rich burning situation where too much unburned fuel was making its way into my cats. What would be causing this situation and what can I do to remedy it so I don't melt my new cats in the future?

I am replacing my spark plugs (with Iridiums), wires, cap and rotor tomorrow, and my thermostat soon to ensure proper operating temperature. When I start the car the fan comes on instantly and I dont think it ever reaches operating temperature. The highest the gauge ever comes upto is halfway between C and normal, usually its just above C. The coolant temperature sensor is functioning properly. Could a cold running situation cause the car to run rich?

There is also a plug that comes off my wiring harness near my coolant temperature sensor that doesnt appear to be plugged into anything, but I dont see anywhere to plug it in. Any ideas on where it goes?

Thanks guys. :)
 

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As seen below, there are two sensors, Engine Coolant Temperature & Water Temperature. One operates gauge and the other goes to ECM:

 

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I'll add that in 1989, the temp sensor used for the gauge was made with a bad crimp, and is known to fail reading-low.

I'd swap that one (the one on the driver's side, with one screw post terminal) before I worried about the indicated temperature much.

RwP
 

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Discussion Starter #4
Oh awesome. Thanks for the information about the temperature sensors, I will compare that picture to what I have under my hood tomorrow. :)

Any ideas about the rich-burn situation?
 

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I had that happen to my Cougar bad ECT.
 

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Oh awesome. Thanks for the information about the temperature sensors, I will compare that picture to what I have under my hood tomorrow. :)

Any ideas about the rich-burn situation?
If not the ECT sensor, new O2 sensors and clean the MAF? Does it have a Check Engine light illuminated?
 

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1997 Thunderbird 4.6, 1998 Mark VIII LSC
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I don't think the 89s had a MAF sensor, IIRC they were speed-density through 90.

Since you mention the check engine light, it might be worth running the OBD-I self tests. Ground the self-test input on the test plug then start the car to start the process. I can't remember all the details since it's been a while since I've done it, but I think fordfuelinjection.com has the process outlined.
 

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Glad to see you got the Bird running again. I'm wondering how long I have until one of mine clogs.
 

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I don't think the 89s had a MAF sensor, IIRC they were speed-density through 90.

Since you mention the check engine light, it might be worth running the OBD-I self tests. Ground the self-test input on the test plug then start the car to start the process. I can't remember all the details since it's been a while since I've done it, but I think fordfuelinjection.com has the process outlined.
Yeh, you're right; you can even see the MAP (yes MAP, not MAF) sensor in the picture above! lol

Hey, maybe it needs a new MAP sensor!
 

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Go get your car tuned this should stop it running so rich.
Yeah, that would cure it from running rich. But it's a band-aid fix at best.

But ask yourself this. With the factory tune, did the car run rich? Doubtful.

Therefore something has failed and is malfunctioning that is causing the car to run rich. What would happen if the problem causing his rich condition got worse after he had it tuned to compensate? The cause of the problem is what should be addressed, not a workaround. Why "fix" the computer when it's not the computer that's failing?
 

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Yeah, that would cure it from running rich. But it's a band-aid fix at best.

But ask yourself this. With the factory tune, did the car run rich? Doubtful.

Therefore something has failed and is malfunctioning that is causing the car to run rich. What would happen if the problem causing his rich condition got worse after he had it tuned to compensate? The cause of the problem is what should be addressed, not a workaround. Why "fix" the computer when it's not the computer that's failing?
Ok go get a new set of O2 sensors when you get it tuned LOL :)
 

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It would be helpful if you could look at the Long term fuel trim, but since its an 89 .. good luck with that.

Your fan shouldnt turn on right away .. depends on the wiring, but some cars you unplug the Coolant temp sensor for the engine ( not the guage ) and the PCM thinks youre either at -40 degrees or 248 .. fan turns on either way as a failsafe. I would figure out why this is happening before changing out plugs and rotor, etc ..

Yes the engine runs Rich when it is cold to get it to warm up faster, if your PCM thinks its cold all the time ....

Need to test those sensors first.
 

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Discussion Starter #14
I will replace the coolant temperature sensors tomorrow, and look into O2 sensors. I will also take pictures of the two plugs that are unplugged and see if you guys know where they go. That would cause my fan to turn on if they are unplugged.
 

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Discussion Starter #15
Yeh, you're right; you can even see the MAP (yes MAP, not MAF) sensor in the picture above! lol

Hey, maybe it needs a new MAP sensor!
Perhaps, from the mechanic I talked to he told me that a rich/lean situation on an OBD1 Ford is an incredibly difficult problem to diagnose. Basically I have to throw sensors at the problem... :tongue:

Glad to see you got the Bird running again. I'm wondering how long I have until one of mine clogs.
Thanks Kelly, its nice being back in my 'bird. :)

I don't think the 89s had a MAF sensor, IIRC they were speed-density through 90.

Since you mention the check engine light, it might be worth running the OBD-I self tests. Ground the self-test input on the test plug then start the car to start the process. I can't remember all the details since it's been a while since I've done it, but I think fordfuelinjection.com has the process outlined.
I will see if they tell me anything, that would make finding a solution to my problem much easier. I've only ever pulled codes with a scanner before, but I dont own one. I'll try the "light blink" method tomorrow. :)

And one other question, where is the thermostat located on my car?
 

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Follow the upper radiator hose to the block; the metal tube that has two bolts with the "bulb" shape under the air bleed bolt (near the gauge sender) is the housing.
 

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Discussion Starter #17
Follow the upper radiator hose to the block; the metal tube that has two bolts with the "bulb" shape under the air bleed bolt (near the gauge sender) is the housing.
Under the orange thing right on top? Awesome. :)

What temperature should I get?
 

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Discussion Starter #19
Hey Dan, this is really weird. Why do I have two coolant temperature sensor plugs? One was tucked back behind where the gauge sending unit is and the other was plugged into the old engine temperature sensor but it comes from some random place under the intake manifold. WTF is this?





(yes, I know the gauge sender was unplugged, I plugged it in after taking the pictures.)
 

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lol... bizarre... Someone was messing with the wiring. Chase down both wires and see where they go. One looks OEM (89) one looks semi-new. Maybe the PO at one time tried to add a aftermarket temp gauge and was tapping the wrong sensor. Who knows.
 
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