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Samus82
Radly

join:2002-01-29
Alsip, IL

RPM jumps while driving.

Ok here is the problem and i dont know where to begin. When i am driving... lets just say 35mph, and keeping it nice and steady not moving my foot at all some times the car will jsut surge up like 500 to 800 rpm. Lets say from 2.5k to 3k and then back down. Almost like it just downshifts out of nowhere for a second and then back. Now i thought it was mabie my foot moving and giving it a little gas, so i drove it on a compleatly flat drive home and it did it a few times. Then to further make it worse i even tried to put it on cruse and sometimes when it jumped rpms and came back it would turn off the cruse. I have a 2002 Grand Am GT and i take beautiful care of it. I dont beat the crap outa it but i do drive in the city alot. It has about 70k in milage. I havent changed the sparkplugs since i have owned it ( i bought it about 1.5 years ago) but i regularly change the oil every 3k.

You guys think this is a tranny problem? Or an electrical problem? Fuel filter? Oxygen sensor? Bad TPS? I know a good amount about cars i just dont know where to start on this one. Im pretty sure my car dosent have a "dipstick" to check the trans fluid color or anything like that. Its sealed. (i could be wrong but i dont see one and im not an idiot) Any ideas where to start and or has anyone ever heard of anything like this?

I have about 3 more years to pay this damn car off and i dont feel like having it crapping out on me. Thanks for the help in advance.
--
Opinion is just a word people hide behind to try and justify them believing stupid things. It sure is easy to believe in something completely and totally stupid, say it's your "Opinion" and then everyone has to respect it.


sdgthy

@optonline.net
Actual speed could be important, what happens if you lightly touch the brake pedal?


Samus82
Radly

join:2002-01-29
Alsip, IL
reply to Samus82
i touch the brake pedal when? The speed i most notice it jumping rps is i think around 35-40mph. I don't think the car speeds up or slows down per se.. Just rpms jumping .5k ish and im not fluctuating the gas pedal, hence it even happens when on cruse sometimes and then the cruse disengages.
--
Opinion is just a word people hide behind to try and justify them believing stupid things. It sure is easy to believe in something completely and totally stupid, say it's your "Opinion" and then everyone has to respect it.


sdgthy

@optonline.net
Sounds to me like you're seeing the result of the torque converter clutch disengaging, tapping the brakes should make it disengage at a time of your choosing.


Bumpin1ohm
Bumpin1ohm
Premium
join:2002-07-15
Aurora, CO
reply to Samus82
wwww.gaownersclub.com

register and post, they will be able to help you.
--
Loud and Clear


Sly
Premium
join:2004-02-20
Chuckey, TN
kudos:1
Reviews:
·Callcentric
reply to Samus82
Does the actual engine speed increase (can you hear it) or does the tach just jump? When you notice the RPM increase, try giving it a little gas. Does the engine speed keep rising like the transmission is slipping or does it pull accordingly?

It could be nothing more than a shift linkage needed to be adjusted or a vacuum modulator valve on the transmission.


TheHarvester
Premium
join:2006-08-25
Dana Point, CA
kudos:3
reply to sdgthy
said by sdgthy :

Sounds to me like you're seeing the result of the torque converter clutch disengaging, tapping the brakes should make it disengage at a time of your choosing.
I agree. If the converter is in lock-up and the brakes are applied (just enough to kick the lights on) it will un-lock the converter.

Are you a 2 footed driver? right foot on gas and left foot on break pedal. Do you rest your foot on the brake pedal? could also be the brake light switch out of adjustment and a slight bump causes the pedal to move enough to trigger the brake lights which will disengage the lock-up and the Cruise control.


Samus82
Radly

join:2002-01-29
Alsip, IL
reply to Samus82
"Does the actual engine speed increase (can you hear it) or does the tach just jump? "

Well i can hear it and feel it a bit. Nothing too bad but definitely noticeable. Both happen speed and tach jump.

I dont put my foot on the brake i drive with 1 foot. My brake light never comes on or so my girlfriend driving behind me says.
--
Opinion is just a word people hide behind to try and justify them believing stupid things. It sure is easy to believe in something completely and totally stupid, say it's your "Opinion" and then everyone has to respect it.


sdgthy

@optonline.net
And you say this happen around 35-40, right about the minimum speed for the converter clutch to lock...

Try lightly tapping the brake pedal under the same conditions and see if the same sort of thing happens. You might even lightly press the brake pedal when you see it happening to see if it stops jumping. Either would indicate you are probably seeing the results of the converter clutch locking/unlocking.


Sly
Premium
join:2004-02-20
Chuckey, TN
kudos:1
reply to Samus82
70K miles... have you ever had the transmission fluid changed? Could be due for one.


Samus82
Radly

join:2002-01-29
Alsip, IL
reply to Samus82
i have never had the trans fluid changed... but i have to check the report i got with the car... the first owner was meticulous and kept records of all the matenence.


Sly
Premium
join:2004-02-20
Chuckey, TN
kudos:1
Reviews:
·Callcentric

1 edit
Be sure to try this also.
said by sdgthy :

Try lightly tapping the brake pedal under the same conditions and see if the same sort of thing happens. You might even lightly press the brake pedal when you see it happening to see if it stops jumping. Either would indicate you are probably seeing the results of the converter clutch locking/unlocking.
I started thinking more about it... I don't know if that car is wired this way but I wonder if the brake switch might be intermittently failing. Let's say you tap the brake and it disconnects the cruise control and it triggers the trans. to downshift. If the switch fails then it could do those things by itself... See if you can get this problem to happen yourself by tapping the brake. Also, if you notice your brake lights coming on by themselves when this problem happens, that would be further evidence that you have a brake switch failing or a wire shorting to ground.
--
"The penalty good men pay for indifference to public affairs is to be ruled by evil men."
- Plato -