I want to check my TPS and see what the readings are. What should the TPS read at idle and WOT? If my TPS is not reading correct under WOT, will that cause a shifting problem? I was told that the TPS has to be set correct in order for me to get rid of my shifting problem under WOT.. true or false? I've done the whole 9 yards as far as having it rebuilt etc.....

Could I have a bad pcm if the settings are correct and my problems still occur?

Thanks
-Mike

 

0 Throttle: .55-.7V
Full Throttle: 4.5-4.6V
Yes, it can cause odd shifts(speaking from experience).

If you have a stock throttle body, you shouldn't have to adjust it. If you upgraded your throttle body, it might be necessary to adjust it. Just test the idle voltage; if it is not correct, you will have to drill the holes bigger in order to adjust(twist) it to the proper position. Just takes patience.

Most likely it is the TPS, so don't worry about it being your PCM until you test it.

 

Anyone else have any input on this?

 

The computer is supposed to interpret anything from .3v-.9v as closed throttle. The computer checks this every time you turn the key ON. .50v-.60v is considered ideal for closed throttle by most people. Check it, like transamdude95 said, and see what you have.
The computer uses the TPS as one of it's inputs for shift timing. The other is MPH.

 

Did you guys get the memo about the new cover letters on all TPS reports? I'll get you all another copy of that memo.

 

Ok, what about WOT, where should it be under WOT? That is where I am having shifting problems is under the WOT. It will not hit at all and I have to back off of it in order to get it to shift, so where should the TPS be under WOT?

Thanks
Mike

 

As Rob indicates, in theory the PCM will accept any closed throttle voltage between 0.20-0.90V, and set that as 0% throttle position (TPP). It then prorates the throttle position by assuming the at WOT, the voltage will have increased by 4.0V over the closed throttle voltage.... so if you start with 0.50V at closed throttle = 0% TPP, you should see approx. 4.5V when you have the throttle all the way open (100% TPP). The key things to look for are both the TPS voltages open and closed, and the TPP % open and closed. Physically check the blades to make sure they are opening all the way when you put your foot on the floor.

 

OFFICE SPACE!!!



-Dave C. '97 Z28

 

transamdude95 provided that info in the first reply.

 

Fred and Rob,

What about the TPS on my 1993 race car?
Specs: 383, 12-1 cr, Solid RR, Turbo 400, ASM Monoblade, race fuel (110).
Tuning by PCMFORLESS.
Going on the dyno tomorrow.

Bottom line, what is the correct to get this car to idle,
1: Turn the idle screw until it idles about 1200 rpms
2: drill a hole in the butterfly plate (monoblade) until enough air enters the intake?


Jim

 

The TPS has nothing to do with the idle speed. It only reads the position of the throttle blades.

You may be referring to the IAC, but you would need to know what the counts are now (per a scanner). I would not drill anything unless it was a last resort.

 

If you're using the stock PCM on your "race car", you should follow the same procedure. Get it as close as you can to 0.65V at idle, make sure its about 4.5V with the blades wide open, and make sure the change in voltage is smooth and linear over the full range of motion. Its obviously not going to have any affect on your trans shifting, since it appears you have a manual valve body on a non-electronic tranny.

Is can affect your idle some. If the closed throttle voltage is over 1.00V, the PCM is going to assume you have you foot on the throttle and will start to add RPM via the IAC in a "follower" mode. It appears to do this for both the throttle position, and based on VSS signal. I don't run the VSS, so its hard for me to see how the combination of VSS + TPP would affect idle speed. But I know that when I had a problem with the TPS voltage being over 1.00V at closed position on my Holley TB, it caused a higher than normal idle speed.

Check the TPS voltage first, to make sure it is under 1.00V. Then start checking the idle RPM and IAC position. What is the idle speed you are trying to achieve? Is this the "target" idle RPM that has been set in your PCM program? Why are you starting at 1,200RPM? Why would you drill a hole - that would only increase the idle speed, and limit the PCM/IAC's ability to control it. You drill the hole if the IAC is wide open and it still won't idle, or possibly to cure a split BLM problem.