Autotap question: throttle position

[TripleTransAm]

First off, how many out there are using Autotap or some other similar tool for diagnostic interfacing with the PCM? If there are enough interested parties, perhaps we could request a 'diagnostic'-specific forum.

My question... with what should be a completely closed throttle, my Autotap is reporting a 20% opening of the throttle blades. What gives?

[MitchB]

OK, where between closed throttle and WOT does your Autotap say you are at WOT? In other words, how much throttle do you have left at the point where it says you are at WOT?

Another thing... doesn't the EEC take a baseline reading of the TPS when you initially power on? So whatever output you may have with the throttle 'closed', the EEC baselines this as 'closed throttle'.

Mitch




First off, how many out there are using Autotap or some other similar tool for diagnostic interfacing with the PCM? If there are enough interested parties, perhaps we could request a 'diagnostic'-specific forum.

My question... with what should be a completely closed throttle, my Autotap is reporting a 20% opening of the throttle blades. What gives?

[TripleTransAm]

I spoke with my favorite tech at the dealer... he thinks the % being displayed is actually a percentage of the total signal coming from the throttle position sensor. In other words, ~20% of the total TPS signal is present when my throttle is closed. Some highway testing shows I get a reading of 90% or higher at WOT.

Another tidbit of info from the tech is how the new TPS units function differently from the previous generation of sensors. The new ones seem to feed some sort of fresh signal to the PCM, rather than take 5 volts from the PCM and feed it through a resistive wiper (similar to a 'volume' knob) and send the resulting voltage back to the PCM. I didn't get all the details on the new method, but it seems they've seen MUCH less failure rates than with the previous types. If anyone knows the details, please share them... I was distracted because I had my little boy with me who was getting kind of nervous with all the shop noises around him as I was speaking to the tech.