1993 LT1

Ok... I am pretty much going through my car, testing everything I can, and if bad or I feel its on the way out, I'm replacing it.

Sooooo, the TPS, I tested it, and for closed I'm getting .54 volts and WOT im getting 4.09 volts. And when you open the throttle slowly the numbers jump "chunky" not smooth AT ALL...

So I decided to replace it.. I know it should read .4v closed and 4.5v WOT. There is no adjustment on the old or new TPS. The holes arnt on some sort of slide and the coolant or vacuum inlet or whatever it is on the TB is in the way of rotating the TPS anyways..


Any help, Idea's?

What TPS are most people buying aftermarket?

Thanks

 

The trick for setting the TPS for maximum performance is really a TPI car thing. The LT1 is somewhat self calibrating. Whatever voltage it reads when the switch is turned to the ON position it will read as 0% throttle and it will go from there.

Therefore what you need to check with a scan tool is that 0% is truly 0, IE don't press the pedal when you turn the key on. If you do it will read something higher as "0" and then when you release the pedal it will go "less than 0" and will instantly set a SES light.

While you've got the scan tool make sure that when you press the throttle down all the way that it actually reads 100%. You can also see that it then reads all points in between.

 

post the year of your car
buy an fsm
when you open it , you think your moving it smoothly , but you're not, thats the reason for it jumping
those 2nd values you posted are for a t'b'i, if yours is a t'p'i the first ones were correct
you're using a multimeter, huh

 

The TPS should have two holes to attach it to the throttle body. One of the holes should be slotted. That's how the adjustment is made. I don't know what year you are working on, but my 85 TPS is supposed to be set for .54 volts closed. It doesn't sound like there was anything wrong with your original.

 

later years dont have the slots, but you can grind them

 

You can but you shouldn't have to. The LT1 PCM only looks for it to be within a certain range when you turn the key to the on position and it will accept this as 0. The stock throttle body and a properly built TPS will fall into this range without adjustment.

Now with that being said, some aftermarket throttle bodies are just a little off and thus may require some grinding / adjustment to get it in that range.

The reason I know all this is because I've seen it first hand. I got a Holley Throttle body years ago for a good price. It's pretty but Holley's QC isn't all that great. The throttle blades wanted to bind up and not let it close 100%, although it was close. If you let off the throttle gently it would close to one point, but if you let it slam closed it would close further. Therefore it would work like this:

Park the car you usually let off the throttle gently. The throttle closes but it's really hung at like 1-2%. Next time you start the car it sees 1-2% as "0." This is all well and good until you get a little frisky and let the throttle slam closed. It now sees -1 or -2% which sets a SES code. Took me a while to figure that out! I was able to tweak the throttle blades slightly to get it to close. I'm thinking then that after that I had to grind the sensor ever so slightly to let it be in the proper voltage range to read this as 0 but then I've slept since then as well.

 

1993, I am using a multi meter... I did buy the only tps the part store had, it was only $30 and seems very cheap, I dont intend on keeping it, but the numbers did climb WAAAAAAY smoother than the stock.. I am still confused about your post, sorry I am still learning about my car.

All the tps's I can see an actual picture for my a 1993 non zr-1 dont have any slotted holes. the zr-1 tps's i can see have slots on both bolt holes. The part that turns on the back side of the stock tps "sticks" and the spring doesnt return like it should so I know it was on its way out the door.

 

I reread his thread twice, and I dont see LT1 anywhere and I read his profile and its not there either, where did I miss it. the .4 to4.5v? my 87 , not a zr1 has both holes slotted

 

When I get home I'll try to remember to get out my FSM to let you know what voltage range it should be in when it is fully closed. So long as it falls somewhere in this range you're good.

 

You didn't. I just knew he had an LT1 from another post.

 

good tech, many thanks

 

- it would be nice to know what year we are talking about. as far as the TP sensor, the full open and full closed values are the only ones to be concerned about. now i have to ask, how are you getting your (voltage) values? what type of meter, and the accuracy of the meter. my 85 had an adjustable sensor, but my 90 didn't. pretty sure the .54 volts and the 4.9 or 5 volts are dead on.

 

Sorry, I'm dumb, whats "TPI"


Well there has to be something up with the TPS or something... I was trouble shooting my car before I ordered the new vented opti spark I just ordered.. The guy I was buying the opti spark wanted to make sure it wasnt a tune issue before I bought his part.

Every now and then, lately, the car didnt want to start right up, you would have to hold the key 5-8 seconds longer than usual. So dude said to hold the petal WOT when starting and the car would go into " clear flood mode" or something like that, and at WOT when starting the car wouldnt give any gas at all to burn up the access gas...

well when I did this I could tell the car was getting a **** load of gas and it actually was harder to start.

SO that tells me the car isnt reading WOT when the petal is all the way down. I tested the tps and it wont go over 4.1v WOT even with the new tps, so I thought I needed to adjust the tps?

 

I had a typo, its .5 closed and 4.09 WOT not 4.9

I had a typo, its .5 closed and 4.09 WOT not 4.9

I had a typo, its .5 closed and 4.09 WOT not 4.9

And I used two different multi meters... Same thing on both

 

Sorry fellas, I just noticed and fixed the typo in the first post.

I am getting .54 CLOSED and 4.09 WOT

There has to be something up that it wont get pat 4.09v WOT?

And I tested the tps, with it off the TB and hooked plugged in it was .4 closed and I turned the whatever with a key and it went to 5v WOT... So I know the sensor works

 

TPI Stands for Tuned Port Injection. It was the standard fuel injection system on Corvettes from 1985-1991.

Maybe, maybe not. The staring voltage will determine the ending voltage. A scan tool will show you the actual percentage that it is reading because the voltage is somewhat meaningless.

 

OK, worst case scenario , when I do scan it and It DID read short of WOT ( I dont know if the value is a number 1-100 or a voltage ) Is the adjustment on the tps end or somewhere else for the computer to get WOT when I'm wanting it..

 

It will show a value of 0-100. If you scan it and it's not reading 100% yet the "0" voltage is within the proper range, then it could be the sensor, not likely since you've replaced it, or possibly the throttle isn't really opening all the way, perhaps a mis-adjusted throttle cable or something like that. (I've also seen that due to my lovely Holley POS).

Now as far as the scan tool, I'm afraid you'll need something like a Mapco scanner, or a Tech II, or a data logging software to know what the computer is giving you. One of these little parts store things that only gives you error codes likely isn't gonna cut it. Got any friends at a GM dealership?

 

BTW, I know from your other post that this thing has ported heads on it, is it the factory throttle body?

When I first got my Holley I could not get my TB to open all the way for anything. I went through the adjustment procedure a dozen times and it didn't work. I even talked with some people at Holley and they knew I was doing the procedure wrong.... SO I drove my car out there, parked it on their checkered floor and had them run through the adjustment. After 3 times when they couldn't get it to work either, they finally tried something else. The Holley TB has 3 settings for return spring tension. Out of the box it was set to the highest setting. When going through all the monkey-motion for the traction control, this is too much tension. They kicked it down to the lowest setting and it worked like a champ.

 

Tested it, you barrrrrrrrrrrrrrrrly touch the petal and that things moves and when the petal is on the floor, the is no more movement in the TB

A very good buddy owns a shop and has a few scanners, if its something he doesnt have the local snap on or matco tool guy will always let us borrow a demo scanner

Good question, I dont think so... The mods were done before I bought it, it has the bolt on "Air foil" on the inside of the TB... But someone thought it would a good idea to paint the fuel rail covers... If you have some stock ones for sale i'd love to buy them ... Any way, they painted the plate on top on the TB also.. So if there was a label its painted over..

The car has a DRM 400 conversion

Heads, Cam ( I wish I knew witch one ), high flow everything in heads, aluminum roller rockers, timing chain and gear ( also wish I knew what specs ) , headers, is lists TB and a few others ..