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post #1 of 25 (permalink) Old 02-06-2008, 11:01 PM Thread Starter
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Losing Rev's Between Shifts

Hey everyone, I am having a problem with my 96. Under light acceleration my car seems like its not holding on to the revs between shifts. I am not sure what this can be, the tranny isn't slipping, good solid shifts no missing gears.

Accelerating lightly 1st goes by fine, then 2nd to 3rd the revs drop to like 1100 from just under 2000 then immediately to 4th (this is around 38 to 40 mph). The car starts shuddering unless I push the pedal halfway to the floor(or hit the OD button) to bring it back into third. Almost like its skipping a gear but I can feel it shifting.

BTW my valve seals are just about gone, so maybe i have oil fouled plugs? My plug wires are about a year old and I just cleaned my MAF. Any help appreciated sorry for such a long post.

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post #2 of 25 (permalink) Old 02-07-2008, 01:17 AM
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i may not be reading this right but could this possibly be the TC shudder?
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post #3 of 25 (permalink) Old 02-07-2008, 02:03 AM
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When my Idle Air Control valve was acting up, it would do that. Clean that, and erase your computer, and drive it for 100 miles or so.

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post #4 of 25 (permalink) Old 02-07-2008, 01:15 PM Thread Starter
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Im pretty sure its not the TC... that was already replaced and I remember what that felt like.

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post #5 of 25 (permalink) Old 02-10-2008, 10:19 AM
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Im pretty sure its not the TC... that was already replaced and I remember what that felt like.
you have done the Mercon V switch right?

that sounds like a bad case of insanely intense tc shudder, alot like what mine was doing when i bought it from some automotively illiterate, i flushed the fluid and put in merc5 and that did the trick

EDIT: do your plugs+wires too

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post #6 of 25 (permalink) Old 02-10-2008, 11:30 AM Thread Starter
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Yea it has MerconV in it. I've noticed that this shudder doesn't happen when its cold, nor under medium to heavy acceleration... Computer issue maybe? I am gonna do wires this weekend and pull my plugs. I'm thinking they have oil on them because I'm burning it.

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post #7 of 25 (permalink) Old 02-12-2008, 01:20 PM
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Same

I'm also having this issue, have you came up with anything yet?

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post #8 of 25 (permalink) Old 02-12-2008, 01:56 PM
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When my Idle Air Control valve was acting up, it would do that. Clean that, and erase your computer, and drive it for 100 miles or so.
where is the idle control valve?.....my car does this as well.

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post #9 of 25 (permalink) Old 02-12-2008, 02:39 PM
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Follow the intake tube and then you'll see a tube go into a black box, and then into something on the plenum. That something is the idle air control valve.

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post #10 of 25 (permalink) Old 02-12-2008, 03:26 PM
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my bet is TC shudder, whether the fluid is responsible or not
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post #11 of 25 (permalink) Old 02-12-2008, 05:59 PM Thread Starter
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the IAC is just for idle as I understand it... if the revs are fluctuating at an idle then the IAC is bad. A friend of mine suggested that the problem could be in the valvebody. I'm gonna check it out this weekend with the diagnostic computer on it and see what I come up with.

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post #12 of 25 (permalink) Old 02-13-2008, 09:46 AM
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my bet is TC shudder, whether the fluid is responsible or not
^^^^what he said^^^^ a diagnostic computer reads codes, is your check engine light on?

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post #13 of 25 (permalink) Old 02-13-2008, 10:27 AM
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Sigh.....

Ok, lets start from the beginning... Your stall speed is around 2000ish depending on how much torque your motor puts out...

You were allowing your motor to make enough torque to make the converter to sit at 2000rpms until the drivetrain speed catches up with the engine speed.

Torque converters can lock up... Meaning the engine speed always is a linear function of the drivetrain speed... X rpms always = Y mph when the converter is locked... Its hard to explain... Basically when the converter is unlocked, Its like you're slipping the clutch in a manual transmission (But no wearing out parts)... You can be at whatever RPM you want at that speed, but depending on how you modulate the pedals, you put out a different amount of power to the ground. Lockup would be the clutch completely applied, holding the engine and transmission spinning togeather. Your car is only programmed to lock up in 3rd and 4th under low throttle.

Torque converter shudder is a condition our vehicles experience when the friction of the torque converter clutch (to lock the converter) and transmission fluid breaks down. As the fluid gets hotter, it doesn't hold as much friction betwen the surfaces. When a torque converter attempts to lock up, and the friction is not high enough between the clutch and the case, it slams between locked/unlocked as it tries to hold togeather (wearing out the clutch even more)

Ok, I hope that helped make a little sense... Let me go through your scenerio...

Quote:
Accelerating lightly 1st goes by fine, then 2nd to 3rd the revs drop to like 1100 from just under 2000 then immediately to 4th (this is around 38 to 40 mph). The car starts shuddering unless I push the pedal halfway to the floor(or hit the OD button) to bring it back into third. Almost like its skipping a gear but I can feel it shifting.
In 1st, and 2nd, your torque converter doesn't lock. That's why it doesn't shudder... After you shift into 3rd, your torque converter locks up (1100rpms corresponds to the speed your drivetrain is actually moving if you had a manual transmission). When you shift into 4th, your engine is still trying to put out roughly the same amount of torque as it was before, but due to the gearing difference of overdrive, the wheels are harder to turn. The torque converter clutch however isn't as difficult... So what happens, is they do battle until you tell one of them to knock it off... When you give the car more throttle, it's really not shifting into 3rd... its sending a signal to the transmission to unlock the converter. The symptoms stop, and the car accelerates to a speed where the converter can hold the applied pressure, the converter locks up, and everything is happy until next time.

Next time it does the shuddering, tap the brakes... The BOO switch sends a signal to unlock the torque converter... That way you can accelerate to a good speed without having to add more torque to the equation, or force the car to downshift.

Go smell your trans fluid... See what it smells like... Also, I'd check your throttle position sensor. It could be out of calibration, and reading lower throttle input than it's really getting, causing you to shift too early. If your coolant isn't **That** bad, a change couldn't hurt... Note, I said change, not flush... Just let it gently drain out, and put more in. A cooler helps a lot. My dad's car has BAD shudder, but in the winter, it doesn't show up for probably the first 15-20 minutes of city driving.

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post #14 of 25 (permalink) Old 02-15-2008, 05:27 PM Thread Starter
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update

turns out it is the TC.. i know... *i told you so* lol.. its locking up too early dropping the revs.

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post #15 of 25 (permalink) Old 02-26-2008, 07:31 PM
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turns out it is the TC.. i know... *i told you so* lol.. its locking up too early dropping the revs.
just a question
how much did that cost you (if you got it repaired)
my car does the same thing but only when its worm (like running after 20 or 30 mins)
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post #16 of 25 (permalink) Old 02-26-2008, 08:11 PM Thread Starter
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Didn't fix it yet. I have to cut out a piece of my exhaust (aftermarket - all welded) to get at the trans and I haven't felt inspired to do it yet.

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post #17 of 25 (permalink) Old 02-26-2008, 08:29 PM
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Didn't fix it yet. I have to cut out a piece of my exhaust (aftermarket - all welded) to get at the trans and I haven't felt inspired to do it yet.
I would love to see what that looks like (your exhaust) because I removed the mufflers on mine and put crome pipes on it (love the sound now ) one more q
do you think that will pass inspection?
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post #18 of 25 (permalink) Old 02-26-2008, 11:52 PM Thread Starter
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As long as you didn't mess with the cats you should be fine. I have my pre-cats, but I removed that huge y-pipe I think is referred to as the 3rd cat. I have true dual into a DI/DO maganflow with an X-Pipe inside out to dual 3" round 18" long chrome slant cut tips. I have the o2 manipulators that fool the computer into thinking everything is cool with the cats. Since you have a 97 I'm pretty sure that they plug into the OBDII port for the exhaust. I get mine privately inspected because I have all my windows tinted so it won't pass. Do some searching there are all sorts of different exhaust setups around these forums.

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Last edited by MidnightSleeper; 02-27-2008 at 12:09 PM.
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post #19 of 25 (permalink) Old 02-27-2008, 01:54 AM
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turns out it is the TC.. i know... *i told you so* lol.. its locking up too early dropping the revs.
FYI the TC cannot be the cause of the clutch locking too early. The application of the clutch is controlled by the TCC solenoid which is in turn controlled by the PCM directly.

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post #20 of 25 (permalink) Old 02-27-2008, 01:55 AM
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As long as you didn't mess with the cats you should be fine. I have my pre-cats, but I removed that huge y-pipe I think is referred to as the 3rd cat. I have true dual into a DI/DO maganflow with an X-Pipe inside out to dual 3" round 18" long chrome slant cut tips. I have the o2 manipulators that fool the computer into thinking everything is cool with the cats. Since you have a 97 I'm pretty sure that they plug into the OBDII port for the exhaust. I get mine privately inspected because I have all my windows so it won't pass. Do some searching there are all sorts of different exhaust setups around these forums.
If you didn't remove the primary cats, why did you mess with the rear oxygen sensors? They monitor the exhaust gas after the front primary cats and nothing else.

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post #21 of 25 (permalink) Old 02-27-2008, 12:07 PM Thread Starter
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If you didn't remove the primary cats, why did you mess with the rear oxygen sensors? They monitor the exhaust gas after the front primary cats and nothing else.
The cats went bad and were turning on the CEL. Eliminators were a cheaper fix.

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post #22 of 25 (permalink) Old 02-27-2008, 12:08 PM Thread Starter
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FYI the TC cannot be the cause of the clutch locking too early. The application of the clutch is controlled by the TCC solenoid which is in turn controlled by the PCM directly.
Well I know for a fact that my TC is locking up earlier than it should, how do I fix this then?

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post #23 of 25 (permalink) Old 02-27-2008, 12:37 PM
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Go smell your trans fluid... See what it smells like... Also, I'd check your throttle position sensor. It could be out of calibration, and reading lower throttle input than it's really getting, causing you to shift too early. If your coolant isn't **That** bad, a change couldn't hurt... Note, I said change, not flush... Just let it gently drain out, and put more in. A cooler helps a lot. My dad's car has BAD shudder, but in the winter, it doesn't show up for probably the first 15-20 minutes of city driving.

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post #24 of 25 (permalink) Old 02-27-2008, 01:55 PM
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Well I know for a fact that my TC is locking up earlier than it should, how do I fix this then?
It could very easily be a TPS or MAF issue. You should clean the MAF sensor if you haven't done so and check the TPS for proper operation.

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post #25 of 25 (permalink) Old 02-28-2008, 01:43 PM Thread Starter
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K perhaps I jumped to conclusions... here's what I did so far:
Checked the plugs/wires...good
Cleaned the MAF
Fluid was flushed last oil change, checked it recently its good, mercon v. Not leaking or anything.
TPS is fine.

I had a buddy of mine that works at the dealer ride shotgun with the diagnostic laptop plugged in... According to him the engine is running fine the trans is shifting fine when its supposed to and the TC is locking up when its "told to" by the PCM. Maybe I'm stupid or something but I'm still confused.

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