I have a 96' Auto

A couple days ago I cleaned out my TB, I have been driving around and the car feels great.

The only thing is, my car is always down shifting....I cant coast at a speed without the car seeming like its confused.

Say im going 45 mph the car will down shift realy fast then go back to the gear it was in, and I did not even press the peddle down...it did this a couple times today on a 10 min drive.

I was wondering. Since I messed with my ECU do you think it may be confused? When I checked my ECU because my Engine light came on a couple days ago. I turned the screw around a couple times, mine does not stop like most peoples say there's dose...could this be it?

I was also thinking, maybe when I re-installed the TB i put the wires on too tight for the gas and the Cruz control?

That do you guys think

 

Your TPS if it's not set correctly will cause that to happen. The ECU doesn't control the tranny. The transmission has it's own controller. It reads signals from the TPS to determine if your coasting or accellerating. A defective TPS will cause your tranny to do some strange things. Sometimes it will not throw a CEL code. The ECU things everything is ok.

Search for a thread, I saw it up the other day called Throttle Shock. There is a TSB in there which explains how the TPS signals cause the tranny to hunt.

 

So what are you saying? My TPS is bad, but its not putting up CEL a code?

What do you mean when my TPS is not set right? Does that mean I did not put it on right? im still a little confused.

 

It's quite possible your TPS is acting funky and NOT throwing a CEL code. The TPS does quite a lot. It has a WOT and Closed Throttle switch as well as a variable resistor which sends a voltage signal to the ECU and the tranny controller. When your off the gas the ECU will see the switch part indicate such. But the TPS may be sending an increased voltage to the tranny controller making the tranny think your accellerating. This can cause the tranny to downshift depending on what speed your traveling at and how much it "thinks" you accellerating.

There are spacific procedures in the Haynes Repair manual which tell how to set and test this switch. You might be better off just getting a new one if your problem gets worse. I'll see if I can dig up that thread with the info on what causes this to happen.

FOUND IT"

NTB97-028 seems to say that there's some problem in the Throttle Position Sensor (TPS) - read on - under closed throttle while "coasting".

With these "coasting" conditions, the ATCU (Auto Trans Control Unit) is reading an *INCREASING* voltage from the TPS (Throttle Position Sensor) combined with the "Closed Throttle Switch" showing "ON". The ATCU "thinks" the vehicle is accelerating (TPS increase in voltage which is probably the defect) when in fact the vehicle is DE-celerating (since the Closed Throttle Switch being "ON" means your foot is off the accelerator).

The TSB says when the TPS measures > 1.0 volt (closed throttle & vehicle decelerating), the ATCU records a trouble code if the vehicle speed doesn't increase within 3 seconds.

It goes over diagnostic tests to monitor the voltages of the TPS, Closed Throttle Switch setting and the vehicle speed, etc.

The bulletin shows a set of example recordings in a specific vehicle test exhibiting the problem which is:
- Actual vehicle SPEED slowing down (foot off gas)
- TPS voltage going UP

The trouble codes are a Red Herring. The more important thing here isn't the 3 seconds or the trouble code thrown or not, but the fact that the TPS seems to be showing 'acceleration mode' when the car is slowing down.

Yes, the trouble codes are bad and the TPS is bad but what else does this influence and what other drivability symptoms could this cause (the throttle shock "coasting" that we all know and love?) This is where the TSB falls flat.

 

http://forums.maxima.org/showthread....threadid=58044

 

did you buy it off of Brett?

 

No it was the one that came with the car, i just wasent sure if i broke it since the screw turns all the way around now.

 

it was a joke, Brett's name on the org is Confused

 

 

Ant