am i missing something here? i cant get new tps to adjust.... disconnect est plug loosen tps with meter on a&b terminals set to .54 volts plus or minus ...engine not running key on in park help....

 

Try the method on my site for adjusting TPS and IAC.

 

Alot of good stuff thanks for putting it together!

 

I'm missing the problem. It looks like you've done it properly, except there is no need to disconnect the EST.

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i could not obtain the correct voltage..

 

hmm...0.54V at idle sounds about right. Since you are trying to adjust, I assume you have an adjustable TPS. You should be able to turn the TPS clockwise and counter-clockwise to adjust the idle setting. If the voltage is not changing, then there is a problem in the way you aligned the TPS to the mount on the TB....

 

http://www.corvetteactioncenter.com/...ht=TPS+voltage

 

Because of your screen name, I'm ASSUMING we're dealing with an '85. Your opening post said, "set to .54 volts". What voltage would you LIKE to set it to? What voltages are you observing as you adjust it?

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i put a new tps sensor on yesterday and could not get adjustment i put old one on and got my .54 volts d.c. i guess it was b.o.b. bad out of box..do i need to set i.a.c. first?

 

Setting the TPS voltage is the last step after adjusting the minimum air flow setting (not the IAC) by using the torx head screw on the TB also changes the TPS voltage setting.

Using the manual procedure for setting the IAC doesn't effect the TPS voltage setting.

Jake

 

Well you need to first set base idle to 450rpm with the IAC pintel fully extended (how to is in my method).

Then you are ready to set the TPS base idle voltage to .54Vdc (or try .65Vdc for a little more agressive throttle response) and set WOT voltage to the max possible.

At normal idle of 600-700rpm the TPS will read around .75Vdc if you use the .65Vdc base idle setting.

 

HUH???

Your IAC MOVES the throttle blades?



Hook up your new TPS and DVOM, with the TPS uninstalled to test it. Move the tang on the back and see if it gives you the full range of voltage readings. Since you don't seem to want to give specifics of what readings you got, I'm guessing that the tang on the TPS wasn't properly engaged with the TB.

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Good point. I've seen a friend mis-install his by not engaging the tang.

Jake

 

Hi 65z01.
I am not sure I agree with the voltage readings.
you are right about the .54V to as it stands in the manual .62V. If you adjust the TPS voltage before the min idle air adjustment and then after the adjustment checks that the TPS voltage is within the window specified. If outside the window readjust the TPS voltage to be between .54 and .62 volts at normal idle 600-700rpm if the chip is programmed so.

 

You do not "set WOT voltage" on your TPS. You only set voltage on TPS for Idle, and only if you have an adjustable TPS.....The TPS is just a resistor strip with two metal prongs that slide over the strip and change the resistance value, which changes the voltage value. One of the wires to the TPS is a 5V reference voltage, which varies from idle setting, let's say 0.6V to WOT, let's say 4.8V......Point is, if you tried to adjust the WOT voltage setting, then you would F'Up your idle Voltage setting.....

 

On my 86, I've been able to adjust both. Moving the TPS Up or Down for the ignition "On"/engine "Off" base setting.

I then used a Fore or Aft movement to get the highest WOT reading I could, which came in at about 4.5 volts; best I could get. The WOT setting is a bit tricky since my TPS doesn't have nearly as much adjustability for WOT as it has for the base setting.

I then recheck the base setting to make sure it wasn't tweaked when I was fooling with the WOT setting.

I've read some posts where guys have used a grinder to elongate the holes to allow for more adjustability on theirs. I tried it on another TPS but doing that didn't seem to make any difference.

Jake

 

Sorry, I didn't mean to imply that there is a direct link between the IAC and the throttle blades. The IAC does not directly effect the throttle blades on a TPI, but it is necessary to extend the IAC pintel to set base idle to 450rpm. While adjusting the base idle it is necessary to tweak the set screw in the left side of the TB; this indeed effects TPS positioning.

Once base idle has been established, then you are ready to adjust the TPS. Setting up the TPS on an '85-'89 Vette is an iterative process. First set the idle voltage (chose .54Vdc or the more agressive .65Vdc, as you like) and tighten the lower set screw a little. Now rock the TPS about the lower set screw while holding the throttle full open till you get the max reading, then tighten the upper set screw a little.

Then check the base idle setting and tweak it as required by slightly rotating the TPS about the upper set screw. It can take several passes between setting base idle and WOT to bet the best TPS setup. Once you are happy with the idle and WOT values, snug down the two set screws and recheck base idle and WOT values one last (hopefully) time.

Though all this tweaking is not absolutely necessary, but it gives the most agressive fuel & timing curves buy letting the ECM see the highest possible throttle advance and going into WOT mode as early as possible.

 

I understand all that, but your previous post said That tells one that the TPS voltage will be different at closed throttle, running, than at closed throttle, off, while adjusting. Sorry, I don't buy that.

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OK, I see what you mean, yet I can even see the TPS values on my AutoXray scanner....hmmm.

Now I'm wondering why the value is higher at normal idle...lol

I thought all the air flow at idle came through the IAC bleed, but maybe the throttle blades are pulled open slightly, that would be the only explanation.

 

I'd say the only reason for the different readings is the calabration of the two different devices, or the different points at which the readings origininate. Or even possibly the available system voltage, due to alternator output.

The idle air flow is a combination of the air admitted past the throttle blades (minimum air adjustment) and past the ECM controled IAC. If "something" is pulling the throttle blades open, what would it be? If so, it would be redundant to the IAC.

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