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Discussion Starter · #1 ·
A month ago I purchased a 2002 3.8L MT Mustang from a relative. A friend pointed out to me today that my RPMs are not dropping when I depress the clutch to shift, or quickly shift into neutral. Since this is my first manual transmission vehicle, I was unaware this was problematic. Because of this problem, the car bucks when shifting into any gear, most likely because the engine is forced down in revolutions per minute to match the gear. Naturally I assumed because I'm a newbie that my shifting habits were bad.

It's not that the RPMs don't fall at all, but rather that it takes a good 3-4 seconds after the clutch is depressed (without any gas) for the RPMs to fall, yet they still fall incredibly slower than they should. In other cars, whenever the clutch is depressed, the RPMs immediately fall down to idle.

The friend who told me of this has a father who is a mechanic, and when I spoke to him about the issue, he offered the suggestion that it could be a computer problem, AKA a sensor is bad or malfunctioning. He mentioned the throwout sensor, which could be the culprit apparently.

What does AFM.com think of this? First of all, am I overreacting because this is standard with all mustangs? Has anyone encountered similar problems? Is this a sign my throwout bearing is bad? The clutch has been replaced within 3 years, so naturally I would assume neither the throwout bearing or clutch is at fault (there is no grinding of gears or scratchy throwout noises).

Any help would be appreciated, however I will be taking the vehicle to a certified mechanic for other reasons besides this issue.
 

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Check your TPS sensor. That's a sign of it going bad
 

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Btw my dad has a 02 v6 5spd and his was doin the same thing... It was the TPS
 

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First, are you aware of what is "normal" for a 96+ MY car? If you are expecting the RPM's to drop to 650-700 RPM's between shifts, that's NOT how it works.

There are two idle modes. Car stopped and car moving. If the car is moving, a fast idle will be used. Fast idle is generally 1100-1400 RPM's. A slow idle will only happen when the car is stopped. The idle behaivor is programmed this way for SMOG reasons.

So.....if this thread is about "normal stock" behavior, every componet could be replaced and it will still do the same thing.

My recommendation? Perform the tests to find out what's wrong with YOUR car. Resist the urge to throw parts at it to get the "quick fix". Sometimes it works but why throw your $$ away?

>>How to trouble shoot idle problems
http://www.allfordmustangs.com/foru...-dieing-idle-idling-rough-14.html#post2260649
 

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Discussion Starter · #6 ·
First, are you aware of what is "normal" for a 96+ MY car? If you are expecting the RPM's to drop to 650-700 RPM's between shifts, that's NOT how it works.

There are two idle modes. Car stopped and car moving. If the car is moving, a fast idle will be used. Fast idle is generally 1100-1400 RPM's. A slow idle will only happen when the car is stopped. The idle behaivor is programmed this way for SMOG reasons.

So.....if this thread is about "normal stock" behavior, every componet could be replaced and it will still do the same thing.

My recommendation? Perform the tests to find out what's wrong with YOUR car. Resist the urge to throw parts at it to get the "quick fix". Sometimes it works but why throw your $$ away?

>>How to trouble shoot idle problems
http://www.allfordmustangs.com/foru...-dieing-idle-idling-rough-14.html#post2260649
Thanks for your insight. I have understood the difference between idles, I should have made myself clearer on that note. And I don't plan on getting any "quick fix" without consulting a mechanic first. Besides educating myself, I am simply just looking for reasons why this problem would occur so that said mechanic can get a head start on aiding me with the problem.

The car eventually gets to the standard moving idle, however it takes a good 6-7 seconds for this to happen after the clutch is depressed or the car is put into neutral, which makes me think it has something to do with the throttle assembly or related parts.
 

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Advice. When taking your car to a professional mechanic, let him/her do their job. You are paying them for their professional experience.

Just like any human being, if you "suggest" what you think the problem is, that's where they will focus.

Use the information to cross check what the mechanic is telling you. This can help avoid un-needed repairs or "parts changing" on your dime.

<jumps off soap box>.
 

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I'M sure it's the TPS... But like I said let us know when you fix it
 

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Discussion Starter · #9 ·
I will surely reply to this when i get it fixed. I tested for error codes, and my computer apparently isn't detecting any flaws whatsoever which is nice........ but I was expecting some TPS error codes. Perhaps the TPS is in the process of failing and isn't being recognized as problematic (if it did fail i wouldn't be able to drive it anyway)

Would it matter if my throttle cable is incredibly loose? I wouldn't think it would matter with this particular problem, but I just noticed it today.
 

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I will surely reply to this when i get it fixed. I tested for error codes, and my computer apparently isn't detecting any flaws whatsoever which is nice........ but I was expecting some TPS error codes. Perhaps the TPS is in the process of failing and isn't being recognized as problematic (if it did fail i wouldn't be able to drive it anyway)

Would it matter if my throttle cable is incredibly loose? I wouldn't think it would matter with this particular problem, but I just noticed it today.
throttle cable? no throttle return spring? maybe but doubt it.. make sure the throttle returns to full closed when you open it. what you might need to do is find out what kind of voltages the TPS is signaling to the computer im not sure though what the normal values are.. iac valve might be a little stuck open as well.. possibly take that off and clean out any carbon deposits that might be stuffing it up.. i have no solid answers though
 

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We had no fault code for ours.. I kept telling my dad what it was. So finally, without getting it tested, we went to autozone and bought another one... Couple screws and it was switched and fixed tight in the parking lot. No problems since. Our had got so bad, that if you were at 3G Rpms, and depressed the clutch, it would raise 300~ Rpms and stay there for like 3 seconds before taking like 5 seconds to fall and then it would idle at 1100 Rpms for a second and then the idle would go to normal then back up to 1100. Started out just like yours, then continually got worse.
 

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Discussion Starter · #13 ·
We had no fault code for ours.. I kept telling my dad what it was. So finally, without getting it tested, we went to autozone and bought another one... Couple screws and it was switched and fixed tight in the parking lot. No problems since. Our had got so bad, that if you were at 3G Rpms, and depressed the clutch, it would raise 300~ Rpms and stay there for like 3 seconds before taking like 5 seconds to fall and then it would idle at 1100 Rpms for a second and then the idle would go to normal then back up to 1100. Started out just like yours, then continually got worse.
Well that sounds almost exactly like my problem...
 

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Guys? You have an 11" clutch/flywheel combo. It will take a few seconds for the inertia to slow down the heavy flywheel when you take the load off of it. The old cheap fix was to get some gasket maker, and make the holes smaller for the IAC.(linked above) It will not cure everything, but it might help. If your rpm's are hanging for 30 seconds, then it would be an issue......

You need to learn how to shift, and it sounds like you are "bucking" the car. It will take some time.....
 

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It's nothing to do with shifting. Inertia won't make the car rev when your foot ain't on the gas....
 

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Discussion Starter · #17 ·
Guys? You have an 11" clutch/flywheel combo. It will take a few seconds for the inertia to slow down the heavy flywheel when you take the load off of it. The old cheap fix was to get some gasket maker, and make the holes smaller for the IAC.(linked above) It will not cure everything, but it might help. If your rpm's are hanging for 30 seconds, then it would be an issue......

You need to learn how to shift, and it sounds like you are "bucking" the car. It will take some time.....
I understand how to shift the car properly, but in doing it properly I severely impede 1. acceleration speed, 2. ability to upshift/downshift quickly, 3. and piss off other people as well as myself... It's incredibly annoying having to slip the car into every gear... It should not be that way. RPM should drop rapidly to enable smooth shifting.
 

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Discussion Starter · #19 ·
Update: checked the TPS a few minutes ago with a voltometer, and the signal wire was reading .88V idle, linearly increased to 4.55V on full throttle, and linearly decreased to .88V on idle throttle.

Doesn't seem like a TPS thing. I ordered an IAC restrictor plate, so hopefully that will do something.
 
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