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97 Mystique 2.0L GS ECT intermittent


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Role
User

Jan 13, 2013, 3:36 PM

Post #1 of 19 (1565 views)
97 Mystique 2.0L GS ECT intermittent Sign In

Hello,

Vehicle: 97 Mystique 2.0L GS

Problem: intermittent temp reading

Actions taken: replaced ECT, replaced wiring from ECT to harness connector.

Temp reads correctly until engine reaches normal temp and then gauge drops to cold.
Gauge does not drop to zero, close but gauge does not bottom out until key is off.

Secondary problem: New MAF makes engine run poorly, engine runs better with old MAF.

Any advice would be greatly appreciated.

Thank you.


Hammer Time
Ultimate Carjunky / Moderator
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Jan 13, 2013, 3:45 PM

Post #2 of 19 (1560 views)
Re: 97 Mystique 2.0L GS ECT intermittent Sign In

Have you verified that you don't have air pockets in the system?



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Role
User

Jan 13, 2013, 3:51 PM

Post #3 of 19 (1552 views)
Re: 97 Mystique 2.0L GS ECT intermittent Sign In


In Reply To
Have you verified that you don't have air pockets in the system




I do not know how to do that, is there a relatively simple procedure that would allow me to check it ?

Thank you.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jan 13, 2013, 3:54 PM

Post #4 of 19 (1545 views)
Re: 97 Mystique 2.0L GS ECT intermittent Sign In

Open the radiator cap when it's totally cold and see if it is full to the top.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Role
User

Jan 13, 2013, 4:14 PM

Post #5 of 19 (1534 views)
Re: 97 Mystique 2.0L GS ECT intermittent Sign In


In Reply To
Open the radiator cap when it's totally cold and see if it is full to the top.


I'm feeling a bit stupid right now:

I cannot find a radiator cap, there is a coolant reservoir but I do not see a cap for the radiator.

The reservoir is at normal level.

Thank you


(This post was edited by Role on Jan 13, 2013, 4:15 PM)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jan 13, 2013, 4:55 PM

Post #6 of 19 (1510 views)
Re: 97 Mystique 2.0L GS ECT intermittent Sign In

Yours likely has a pressurized tank so you are probably right and the level is OK.

I believe that engine uses a different coolant sensor for the gauge than it uses fir the computer.

Look for another sensor in the left side (front of car) of the head.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Role
User

Jan 13, 2013, 5:17 PM

Post #7 of 19 (1504 views)
Re: 97 Mystique 2.0L GS ECT intermittent Sign In


In Reply To
Yours likely has a pressurized tank so you are probably right and the level is OK.

I believe that engine uses a different coolant sensor for the gauge than it uses fir the computer.

Look for another sensor in the left side (front of car) of the head.


The service manual says there is only one ECT sensor.

But there are two circuits, one for the gauge and one
to the PCM, it runs rougher when the gauge drops to
cold so the initial #$$umption is the circuit to the PCM.

Side note:
Any idea why a new MAF (tried two of them) makes it
run rougher than the 16 year old original ???

Thank you.


(This post was edited by Role on Jan 13, 2013, 5:18 PM)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jan 13, 2013, 5:34 PM

Post #8 of 19 (1495 views)
Re: 97 Mystique 2.0L GS ECT intermittent Sign In

I'm not sure what manual you are looking at but I have Alldata which is factory info and it keeps referring to an "instrumentation ECT sensor" and the wiring diagrams show different circuits.







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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Role
User

Jan 13, 2013, 5:47 PM

Post #9 of 19 (1490 views)
Re: 97 Mystique 2.0L GS ECT intermittent Sign In


In Reply To
I'm not sure what manual you are looking at but I have Alldata which is factory info and it keeps referring to an "instrumentation ECT sensor" and the wiring diagrams show different circuits.

I purchased the factory engine manual, it show one ECT sensor for this model year.

(I'm still waiting on the factory Electrical/Vacuum manual which may have more info)

The top diagram is right on the money, including the color coding on the wires.

But the bottom diagram shows a sensor I cannot locate.

Is it possible the bottom diagram is for a earlier/later model ?

Thank you.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jan 13, 2013, 5:50 PM

Post #10 of 19 (1485 views)
Re: 97 Mystique 2.0L GS ECT intermittent Sign In

No, that's not possible. We pay serious money for accurate information.
There is another sensor there somewhere.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Role
User

Jan 13, 2013, 5:52 PM

Post #11 of 19 (1481 views)
Re: 97 Mystique 2.0L GS ECT intermittent Sign In

  
Addendum,
It looks like circuit C1004 might be the problem.

Guess I will need to wait for the electrical manual.

Any ideas on the MAF situation I mention above ?

Thank you.

Edit: OOPS, C1004 is the connector to the instrumentation from the PCM/ECT...


(This post was edited by Role on Jan 13, 2013, 5:57 PM)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jan 13, 2013, 5:55 PM

Post #12 of 19 (1478 views)
Re: 97 Mystique 2.0L GS ECT intermittent Sign In

Here I even have the different part numbers

Temperature Sensor (Gauge) Temp Sending Unit F5RZ10884A $44.70


Coolant Temperature Sensor/Switch (For Computer) Coolant Temp Sensor F5AZ12A648AB $29.04



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Role
User

Jan 13, 2013, 6:00 PM

Post #13 of 19 (1474 views)
Re: 97 Mystique 2.0L GS ECT intermittent Sign In


In Reply To
Here I even have the different part numbers

Temperature Sensor (Gauge) Temp Sending Unit F5RZ10884A $44.70


Coolant Temperature Sensor/Switch (For Computer) Coolant Temp Sensor F5AZ12A648AB $29.04


I replaced the second item.

Now I need to find the first.

Thank you again for your time and trouble.

Edit: I have no idea where the sending unit is, (Temp Sending Unit F5RZ10884A), can you tell me where to find this part on the car ?
(10883 is the gauge in the instrument cluster but I cannot locate 10884)

Thank you.


(This post was edited by Role on Jan 13, 2013, 6:12 PM)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jan 13, 2013, 6:22 PM

Post #14 of 19 (1463 views)
Re: 97 Mystique 2.0L GS ECT intermittent Sign In

Alldata says it's on the left rear of the engine.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Role
User

Jan 13, 2013, 6:28 PM

Post #15 of 19 (1458 views)
Re: 97 Mystique 2.0L GS ECT intermittent Sign In


In Reply To
Alldata says it's on the left rear of the engine.


I found it !

It is on the bottom of thermostat housing, which I can actually get to from the top.

Thank you very much !!

Now, if I can figure out the MAf weirdness. :D


Discretesignals
Ultimate Carjunky / Moderator
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Jan 13, 2013, 6:31 PM

Post #16 of 19 (1453 views)
Re: 97 Mystique 2.0L GS ECT intermittent Sign In

Are there any trouble codes stored in the PCM? Seems weird that the engine runs funny when the gauge drops.





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Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jan 13, 2013, 6:33 PM

Post #17 of 19 (1450 views)
Re: 97 Mystique 2.0L GS ECT intermittent Sign In

That has nothing to do with the MAF. It's a mixture problem from something else. It just happens to run better in default mode.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Role
User

Jan 13, 2013, 9:02 PM

Post #18 of 19 (1436 views)
Re: 97 Mystique 2.0L GS ECT intermittent Sign In


In Reply To
That has nothing to do with the MAF. It's a mixture problem from something else. It just happens to run better in default mode.


Thank you for that.

Where would I begin in the search for the mixture problem ?

There are so many sensors I am not sure where to start the diagnosis.


Role
User

Jan 13, 2013, 9:17 PM

Post #19 of 19 (1434 views)
Re: 97 Mystique 2.0L GS ECT intermittent Sign In


In Reply To
Are there any trouble codes stored in the PCM? Seems weird that the engine runs funny when the gauge drops.


I will get the codes on Wednesday when I can stop by Autozone. (they said they would pull the codes for no charge, but they cannot do a reset)

Currently, at start up, winter conditions, the engine has to be kept at about 1500-1750 rpm to get to the mid point of it's heat curve and then it idles decently but when it reaches "normal" temp the gauge drops and it idles pretty rough down around 750-500rpm and will stall intermittently if I don't keep my foot in it.

Caveat: I have not worked on a post 1990 engine (PCM), until now, so I'm stumbling through the diagnosis procedure.

In the current economy I am forced to try and repair this myself so please bear with my ignorance.

Thank you.






 
 
 






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