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2004 Corolla sparatic upshifting hang up


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dmac0923
Enthusiast

Jan 16, 2010, 1:57 PM

Post #1 of 4 (1659 views)
2004 Corolla sparatic upshifting hang up Sign In

2004 toyota corolla 1.8 4 cyl automatic. 78,000 miles

while driving around the trans will get "stuck" in gear and not shift at its normal shift point. If you let off the gas and reapply the gas the car shifts into the right gear.

i believe its from the 3-4 shift but it happens so sparaticly its hard to duplicate and when it does happen you didnt pay attention which gear your in.

it happens when the trans is both hot and cold.

no blinking O/D light.

I think its probably a sticky 3-4 (or which ever gear set it is) solenoid that is getting hung up every once in a while.

i know back in the old days for sticky lifters you could run a quart of mystery oil or transmission fluid to try and clean the varnish off the lifters.

is there any deterdent or additive out there that could clean this up.

i know its probably just putting a bandaid on a knife wound. but we have a wedding coming up and i cant really swing rebuilding the tranny right now
__________________________________________________
2015 Jeep Grand Cherokee
2002 Ford Ranger
2004 Toyota Corolla
1969 Ford Mustang Mach 1


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jan 16, 2010, 4:39 PM

Post #2 of 4 (1653 views)
Re: 2004 Corolla sparatic upshifting hang up Sign In

Crude basics of when automatics shift:

1. Load on engine which is determined by manifold actual vacuum no doubt converted to an electrical device.

2. Throttle position.

3. a governor sensing rpm that forces an upshift at maxed out RPMs.

All of that was mechanical back when and now electrical in most everything which is more accurate.

If fluid color is good I doubt sticking but if you must a product called Trans-X is good with PS and automatics for sticky varnish problems usually caused by heat and time.

Because you said it's erratic and letting off gas would rise vacuum I'm suggesting you look for a vacuum item directly to actual intake manifold for the trouble. High vacuum will encourage an upshift. Letting off gas spikes vacuum, and engine tilts a tad so a weak/cracked line or some dang thing could be the fix?? Can't think of much else if fluid color and smell is good.

These are generally good cars but unless you know everything about how it's been treated it could have a worse problem.

I'm not a trans person - all that from old school training on how they work. Good luck. Perhaps someone knows of something common that could do this other than as mentioned better that myself,

T



dmac0923
Enthusiast

Jan 19, 2010, 11:09 AM

Post #3 of 4 (1644 views)
Re: 2004 Corolla sparatic upshifting hang up Sign In

hey tom, lol my dad said sounds like the vacuum modulator but then i had to update him on the new electronically controlled transmissions.

the fluid is at the proper level. coloring is a little off not the bright red of new fluid, but it rarely is even after a service. smell is ok, nothing overbearing.
__________________________________________________
2015 Jeep Grand Cherokee
2002 Ford Ranger
2004 Toyota Corolla
1969 Ford Mustang Mach 1


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jan 19, 2010, 2:12 PM

Post #4 of 4 (1630 views)
Re: 2004 Corolla sparatic upshifting hang up Sign In

So true - the good old vacuum modulator. Remember one way they failed would suck trans fluid and turn your car into a mosquito fogger! You could easily adjust those too for shift points that suited you also! It's still taking the same info but near everything is going to convert it to an electric signal then let a puter make the call.

Used to adjust bands too when it took a pause between shifts to speed up the transition! Egad - feel old enough?

T







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