Ok heres the deal. Correct me if i am wrong but our cars are supose to go into open loop at WOT right? Well on my car when i got WOT it stays closed and my TP sensor only goes to 99%. Isn't it supose to be 100% I am trying to figure out why my car has been running poorly. Very bad throttle response every know and again. Its kinda comes and goes. Its werid. I am wondering if its not going into open loop would be causing this problem.
What do you guys think?
Thanks Brad

 

Did you look at AutoTap to see if it is in "closed loop"? If so, you are confused because of the way GM uses the words.... GM refers to "open loop" as the start-up mode, before the O2 sensors are active and coolant temp come up to temperature. When they come up to temp, closed loop is "enabled".... O2 sensors active, coolant temp above the minimum (120-140degF) and the timer from start has timed out. In closed loop, the PCM uses the feedback from the O2 sensor to adjust the fuel trims.

When you go WOT (And this is NOT only 100%.... there is a table of minimum TPP percent vs. rpm), the O2 sensors are ignored, but GM does NOT call this "open loop".... they call it "power enrichment mode". But, since all the minimum conditions for closed loop operation are still met (coolant temp, O2 sensors active), the flag in the PCM shows "closed loop enabled". And that is what you see in AutoTap.... not an indication that you are actually in "closed loop", but an indication that the minimum conditions for closed loop have been met.

May sound screwy, but what you are seeing is a common point of confusion the first time people look at a data log.

And, not all scan programs show "100%" TPP at WOT, some of them only show "99%".... its a function of the software, not a problem with the TPS.

Just to put your mind at ease, the table in the 94's shows that up to 2,800rpm, any TPP over 66% is considered "WOT". At 4,000rpm, you only need to reach 38% TPP to enter PE mode, and at 5,600rpm you only need to be at 28% TPP. I suspect your 97 is similar.