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Old 01-05-2008, 11:42   #1 (permalink)
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86 Tempo- rough idle, poor mileage, soot in exhaust

Hello,

I have an 1986 Tempo with the auto tranny.

The car has numerous performance problems. It idles rough, the idle will also idle high and then idle so low it stalls. The car is also hard on fuel and has black soot from the tailpipe. You can smell how rich the car is running from the exhaust.

Any suggestions on where to start. It has the CFI fuel system, 200,000 kms on the engine and there is no check engine light.
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Old 01-05-2008, 12:29   #2 (permalink)
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Exclamation Re: 86 Tempo- rough idle, poor mileage, soot in exhaust

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Originally Posted by bkoz
Hello,

I have an 1986 Tempo with the auto tranny.

The car has numerous performance problems. It idles rough, the idle will also idle high and then idle so low it stalls. The car is also hard on fuel and has black soot from the tailpipe. You can smell how rich the car is running from the exhaust.

Any suggestions on where to start. It has the CFI fuel system, 200,000 kms on the engine and there is no check engine light.
Couple suggestions.
1. O2 sensor could be on the way out.
2. This one may be more likely-MAP sensor is on the way out. I had a bad MAP sensor on my old 1990 Taurus GL years back and it was running just like yours, minus the black smoke. Mine was a 3.0L Vulcan V6 but yours has one too. It is located on the firewall, center near the EGR solenoids, it has a single vacuum line and a connector going to it. You have to test the voltage reading of it, back probe the center wire, the voltmeter should read the right voltage at the altitude you are located at. Here's the chart:
Can vary +/- about .04 V
Altitude above sea level (FT.) Voltage
0 1.59V
1000 1.56V
2000 1.53V
3000 1.50V
4000 1.47V
5000 1.44V
6000 1.41V
7000 1.38V
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Old 01-05-2008, 16:00   #3 (permalink)
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Re: 86 Tempo- rough idle, poor mileage, soot in exhaust

Great advice. I will check the MAP sensor tomorrow.
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Old 01-06-2008, 13:56   #4 (permalink)
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Re: 86 Tempo- rough idle, poor mileage, soot in exhaust

I probed the MAP sensor while that car was idling and got 2.59V

I also found bad vacuum hoses to the MAP sensor and the PCV valve.

I found that the fuel injector was dripping when the car was shut off.

I found the EGR Valve Position Sensor unplugged.

I pulled the codes and this is what came up when the car was running:

21 - Coolant Temperature Sensor out of specified range
42 - Fuel mixture rich
52 - Power Steering Pressure Switch out of range.

I will replace the MAP sensor and the vacuum hoses and try some used injectors and see if there any changes.

Does anybody have voltage specs for the Coolant Temperature Sensor and Power Steering Pressure Switch?
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Old 01-06-2008, 14:06   #5 (permalink)
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Exclamation Re: 86 Tempo- rough idle, poor mileage, soot in exhaust

Quote:
Originally Posted by bkoz
I probed the MAP sensor while that car was idling and got 2.59V

I also found bad vacuum hoses to the MAP sensor and the PCV valve.

I found that the fuel injector was dripping when the car was shut off.

I found the EGR Valve Position Sensor unplugged.

I pulled the codes and this is what came up when the car was running:

21 - Coolant Temperature Sensor out of specified range
42 - Fuel mixture rich
52 - Power Steering Pressure Switch out of range.

I will replace the MAP sensor and the vacuum hoses and try some used injectors and see if there any changes.

Does anybody have voltage specs for the Coolant Temperature Sensor and Power Steering Pressure Switch?
When you pull the codes with the engine running, you have to turn the stering wheel left to right, that would be why the pressure switch code set if you didn't turn it. If the engine was not warmed up during the self test the coolant temp sensor code will set. You test the MAP sensor with the key on, engine off, not running. The fuel injector shouldn't be dripping with the engine off. Bad vacuum hoses to the MAP sensor will cause poor running.
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Old 01-09-2008, 16:34   #6 (permalink)
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Re: 86 Tempo- rough idle, poor mileage, soot in exhaust

I have installed a used MAP sensor, a used injector and replaced the vacuum hoses and the car runs 100% better. Very nice.

tbird100636 - do you know if the MAP sensor voltage value will change as you rev the engine?? And I will re-check the codes with you advice on the PS switch and the coolant temp.

Thanks.
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Old 01-09-2008, 18:02   #7 (permalink)
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Re: 86 Tempo- rough idle, poor mileage, soot in exhaust

the voltage wont change if anything at all, the resisance in the signal will.
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