TPS set at .42, why?

[scottyb]

I noticed my IAC a bit high yesterday at around 45, so I adjusted the throttle blade stop screw out to get it around 28 . Of course, this means the TPS is now at .48 . I did not adjust the TPS sensor yet and decided to drive and see how it is. Well, it now runs smoother than ever! No stumble and idle for startup and warm hasn't changed.

What is the reason for the ".42" standard setting? I assume that what really counts is the ECM to see "idle", so what is the TPS threshold for it to be considered off-idle?

Does anyone not follow the ".42" guideline?

 

[Just a Six??]

Like you said guideline. Steve Wood has a site called
(Vortex Buicks?) & TPS can be 38-48 with the high setting being 3.8? - 5. Computer doesn't really care as long as your in the areas. Just so it recognises a turn on point. Find his site as my explanation sucks I'm sure.

 

[d0n_3d]

no the tps needs to be set at .40-.44 at IDLE because if it's at .46 or higher then the ECM thinks you are no longer idling and it screws up the idle speed...mine is set at .42 and iac counts are near 20 at idle when warm...

now at WOT as long as the TPS is over 4.0 then you are fine...almost all the chips for our cars made today use power enrichment mode starting at 75% throttle which would be like 3.75 TPS voltage but to be safe keep it at 4.0 or higher...don't be fooled by people saying that you HAVE to have it over 4.50 or something...as long as you are in power enrichment mode, it doesn't matter if you are at 4.2 or 4.8 TPS...my WOT tps is at 4.60 so no problems here...

 

[d0n_3d]

Originally posted by scottyb
I noticed my IAC a bit high yesterday at around 45, so I adjusted the throttle blade stop screw out to get it around 28 . Of course, this means the TPS is now at .48 . I did not adjust the TPS sensor yet and decided to drive and see how it is. Well, it now runs smoother than ever! No stumble and idle for startup and warm hasn't changed.

that's because the ecm has adjusted the idle to be a little higher so that's why you feel it a little smoother...but don't be fooled...your fueling will be totally thrown off at startup and also while cruising around...eventually you will be driving around and come to a stop and the tps is gonna be at .48 or whatever and it's gonna idle at 1k rpms or higher and the car will want to keep jumping off the line because of that high idle...set it to .42 and if your iac counts are between 10-30 then you should have a fine idle...if not you have a problem elsewhere in your motor...

 

[scottyb]

Re: Re: TPS set at .42, why?

Originally posted by d0n_3d
that's because the ecm has adjusted the idle to be a little higher so that's why you feel it a little smoother...but don't be fooled...your fueling will be totally thrown off at startup and also while cruising around...eventually you will be driving around and come to a stop and the tps is gonna be at .48 or whatever and it's gonna idle at 1k rpms or higher and the car will want to keep jumping off the line because of that high idle...set it to .42 and if your iac counts are between 10-30 then you should have a fine idle...if not you have a problem elsewhere in your motor...

I agree with that...but the idle is the same. Cold start is the same. Only change is tip-in stumble gone. I read on Steve's website that the ECM reads the initial TPS at startup, considers that 0% throttle, and scales from there. I just wondered if .48 is too high for initial scaling. So far I'd say it's ok, but his site said .46 is the threshold. I will adjust it down, but I won't tinker with it again until I can give the TB and IAC a good cleaning.

 

[zam70]

Make sure you are checking the TPS voltage with the engine OFF. When started, it will read .2 higher.

I always set mine at .44 engine off, .46 engine on. If you're are setting it at .48 engine off, when you start the engine you will be at .5 which will take you out off idle mode.

I personally have found .48-.42(engine on) works fine/the same.