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8 DAY HOMECOMING
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13,107 Posts
Discussion Starter #1
Figured Technical place would be a decent place to start...

I guess the problem started yesterday...Whenever I am driving at 50 mph and up it shifts between 3rd and 4th gear. So say I am driving at 70 mph and am letting of the gas and then getting back on it to stay around 70. It will shift down to 3rd for approximately 4 seconds, then shift back up to 4th...

Same at 50-55, it will downshift for about 4 seconds then shift up to 3rd.

But if I stay on the gas say to get up to highway speeds then I have no problem at all with the shifting, just when I am cruising. It is fine in overdrive, just seems to be that last gear.

I am going to take the cables off the battery tomorrow to reset the ECU and let it idle for a while and see if that helps it any...

Any ideas on what this could be or what it causing it? 2002 Automatic SPI. 70,000 miles.
 

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8 DAY HOMECOMING
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13,107 Posts
Discussion Starter #2
I am getting no codes being thrown. Will clean the TB with carb cleaner tomorrow as well and look at the throttle cable. Hope that fixes it.

Will still like to see what you guys think.
 

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8 DAY HOMECOMING
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13,107 Posts
Discussion Starter #3
Bump for the morning risers...
 

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8 DAY HOMECOMING
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13,107 Posts
Discussion Starter #5
What do you mean by Kick down cable? I reset it, put the intake back on. Will be driving it tomorrow to see if that fixes it.
 

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637 Posts
Some older transmissions have a cable called the kick down cable. It ties up with the throttle so when you step on the gas enough, it will downshift. If not adjusted properly, it could be doing strange things. But I'm not sure if this car uses one or if its all computer controlled
 

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8 DAY HOMECOMING
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13,107 Posts
Discussion Starter #7
I have a cable throttle body..if that is what you mean.

Does the TB cable, when I open it it opens fine. But i can pull the cable the other way and get probably an inch of slack when i pull the cable the other way. I don't know how to explain it better...

Could the slack be part of the problem? how could I reduce the slack in them?
 

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Unrelated IMHO. Pull on the cable & you're just raising the gas pedal from it's normal position.

There isn't a "kick down cable" in these BTW - all electronic. That's why some guessed at the TPS since the computer uses throttle position for both fueling/spark & transmission control. "Kick Down" would be when it sees the throttle depressed and you aren't moving as you should be because the gear selected is too high.
 

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If the engine isn't outputting the power it is supposed to, the trans will start downshifting when it normally wouldn't.

Not all weird trans downshifting issues are the transmission.
 

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8 DAY HOMECOMING
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13,107 Posts
Discussion Starter #10
Thanks for the replies. I will be driving it today and seeing if it is still doing it.

Now I did change the fuel filter and it started after I did that. Is there anything I could have messed up there to make it run funny?

I will look into the TPS.

The engine is outputting power like it does on any other day. Nothing unusual in regards to that.

It only does it at cruising speeds.
 

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8 DAY HOMECOMING
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13,107 Posts
Discussion Starter #11
Resetting the ECU didnt work. Its doing it again today.

Could it be possible that it is the TPS?
-Im not surging at idle
-Idle isn't rough
-Acceleration is just like it always is, no issue there.
 

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8 DAY HOMECOMING
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13,107 Posts
Discussion Starter #14
Thanks Mandroid. I looked into it further. Probably replacing the TPS.
 

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8 DAY HOMECOMING
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Discussion Starter #15
This pretty much hits the nail on the head for what is happening.

If it was a TPS you'd be experiencing the typical TPS failure that doesn't throw a CEL. That is basically that the TPS wears out in the place where the throttle spends most of it's time. You'll notice hiccuping and sputtering during normal driving, and it will want to die when you come to a stop like you're experiencing. You can also sometimes see codes for O2 sensors and fuel delivery because the TPS is telling the PCM that the throttle is open further than it actually is- so you get rich conditions. The PCM adjusts for that, and now it's too lean. The same goes for when you come to a stop, the TPS is still showing the PCM that the throttle is open slightly, and so the engine floods. The PCM is like WTF! I'm dieing here!!! so it kicks up the IAC to boost rpms. About that time the sluggish TPS starts responding that it's at idle, and all is good- no code thrown.

About the only way to repair this problem is to eliminate all other causes, then replace the TPS, or you can take the chance and throw a TPS at it to see if that fixes it. Just be sure that you know that some problems mimic others, and you might be wasting your money. However, a sluggish TPS is typical for older cars, so even if you get one and it doesn't fix anything- you've likely saved yourself from having the problem show up a while after you make this repair and completely confusing you since you thought you already fixed it- and that fix is still good after you check.
 

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8 DAY HOMECOMING
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13,107 Posts
Discussion Starter #18
This is what I need right? Motorcraft DY871 Throttle Position Sensor
 

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8 DAY HOMECOMING
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13,107 Posts
Discussion Starter #19
Replaced TPS today. Reset ECU.
 

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8 DAY HOMECOMING
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Discussion Starter #20
Problem has been solved. Thanks everyone.
 
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