GS Stopped Auto-Downshifting, Did I Break it??

[stevencovert]

My GS has always idled a bit high at cold startup, about 1900 RPM, then drop down after a minute or two to 1500 RPM where it should be. My daughter bought a GS, I noticed that it idled right where it should when started cold. I never had a reference, thought mine was normal.

So I looked at the service manual and thought my throttle position sensor may be off. I know the ECU sets the idle speed, I thought some input might be a tad off. Spec is .5V to .7 volts no throttle. Mine was a tad high, .85 volts. I tweaked it down to .7 and started a ride - engine was hot so wouldn't be able to tell until next day. Then I noticed it didn't shift down by itself! I can use the paddles to downshift fine, and it will downshift sitting at a stop sign, though it takes about 4-5 seconds holding the paddle shifter.

All the vacuum lines were replaced with good silicon a few weeks ago, so it shouldn't be the MAP sensor. They are still tight and brand new. So I'm left thinking this little tweak freaked out the computer? Maybe doing it while engine running made it crazy? I did move it too far and it idled rough, only needed the slightest twist. Gonna cost me $40 to find out to get the TPS reset to find out. Waiting for brake pads & tires to install then take to dealer for reset.

I'm just curious if anyone has run into your SE5 deciding not to downshift by itself, and what the cause was.

 

[SpyderAnn01]

I think your tweaking is your problem. Can’t you undo your changes?

 

[stevencovert]

I did try to put it back, no luck.

 

[stu]

I work on the last thing that was done as it's most likely caused the current fault. Go back and retest your settings. If you can get BUDS on to i, then get the tps sensor setting checked, it can be reset. Also, you mentioned the vacuum hoses were replaced - those have to be an exact length both sides or the MAP sensing will be off also. BUDS will show you if the manifold vac is the same from side to side. Check the throttle bodies for dirt and oil build-up around the plates and the venturi, that will cause throttle hang up if the vacuum's not right. You can also check the throttle setting on BUDS to see the percentage of opening between closed to full.