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Well I found this thread while searching possible problems with my transmission after having transmission flushed (see rant in maintanence) but my question is, is this tweaked during a transmission flush or is this sudden jerking into gear on cold starts a problem from having my tranmission serviced at a car wash?
I plan on doing this tweak but will I only be putting a bandaid on something that could turn out more serious in the future???
so would this have a similar effect as adjusting the line pressure via the adjustment screw in the trans?
Would there be any adverse affect to raising the line pressure via this method other than a harder shift?
hmm then what explains those.. CRAZY Jolts that happen once every other week?
like i remember warming up my car.. n then got in to drive. Pop it in reverse holdin on brake. n BAM the car jolts back like.. a big sudden shock.
wierd? or something is bad?
but this mod.. has anyone turned it right?? haha
I just tried this today on the SC400 and turned it counter-clock wise it fixed the clunking when shifting in all gears from P to 1st. I think a good transmission drain and fill (several times) really helped. Cheers!
I did this today, and it does feel better; as if the shifts are smoother.
The idle upon start-up was at 1200, but after a brief drive (1.5mi) it fell down to 800 at the red light.
Switching from D to R and back again, seems smoother also; no "clunk" ...
So I think it worked; however I didn't have to move it very far. The TPS was just short of fully-left; I only had to adjust it about 1/4". Perhaps the original owner attempted this mod, 'cus I've never touched the TPS until now.
Just to be certain though, since mine's an SC300, which one's the TPS?
I assumed it's #2, since thats the same side as the throttle cable ...
If that's the case, then what's sensor #1, and what happens if I adjust that also?
I can't say this tip makes any sense to me, although I didn't read pages 2 and 3. Adjusting the TPS doesn't seem like it should have any affect on the transmission's smoothness of shifting -- that's what the transmission throttle cable is for -- but would have other adverse drivability effects. Maybe one is covering for the other, but it seems like the wrong way of going about it.
Im still having hard jerk from park to drive. The detent cable barely has any tension on it at idle and moving the TPS did not fix the prob. I also have new trans. mount and steering rack bushings.
Other than the rough shift into drive, my car runs excellent. Does anyone think my TPS could be faulty and not affecting transmission?
From everything I've read, that's a mechanical thing and is just the nature of the transmission. To prove otherwise would probably require input from one of the few people who bought their SC new and can vouch for how it behaved initially.
I had a 95 SC400 for 4yrs, always shifted into drive smoothly. I owned this car for 4 yrs. and it did the same, until the engine and trans, were removed from the car. I always thought that the TPS was a major player in the performance of OBD1 cars, because such a big deal is made out of the exact setting of them. Now im remembering that the MAF, temp. sensor, ECU and 02 sensors are prob. bigger players of the engine fuel/air control than the TPS?
So I just watched a video on rockauto, concerning an airtex TPS and it said the synptom caused by a faulty TPS is hesitation on acceleration.
That would be the normal symptom attributed to it. Unless someone comes along with a solid explanation of how the TPS affects the smoothness of the shifts themselves, I call B.S.
Before someone else calls it BS and might mislead people , The TPS, indeed does AFFECT automatic transmission SHIFTING . There is NOTHING MECHANICAL on the SC400 A340 transmission SHIFTING SCHEDULE . The throttle position cable on these transmissions control the line pressure only, it does not affect shift points. Shift points are determined by throttle position signal / information from the TPS sensor .
The Throttle Position Sensor (TPS) whether it is for ODB1 or ODB2 cars , being a potentiometer (varying resistor) , provides a varying voltage signal both to the Powertrain Control Module (Engine ECU) and the Transmission Control Module (Transmission ECU). In this case for the 1UZFE , both control modules are on the same ECU.
1) It tells the Engine ECU how much the throttle plate is wide open and in turn the ecu estimates how much air is coming in so it can adjust fuel injection and ignition timing accordingly.
2)Automatic Transmission shifting schedules or what we call shift maps are tuned / programmed or are based on the LOAD of the car. Such information is provided to the Transmission Control Module ALSO by the Throttle Posistion Sensor (TPS). Exactly the reason why when you adjust that TPS , you vary the voltage signal and thus shift points vary. That is how a 1UZFE automatic transmission determine its SHIFTING SCHEDULE.
In short , the TPS Sensor output signal is shared by the Powertrain and Transmission control modules which for the 1UZFE is all in one control box we call engine ecu.
Thus , IT MAKES SENSE why adjusting the TPS either clockwise or counter clockwise changes how the transmissions shifts.
11-18-08, 10:56 PM
