Hi. I have Pontiac Firebird with 305 TPI. Engine losess some power when it is warm. I replaced o2 sensor, sparks, sparkplug wires, ignition module, cap and rotor, Air filter, alternator, battery, ECM, IAC, new Throttle Body Gasket and cleaned Throttle Body, cleaned all connectors under the hood and grounds at the back of engine and in the engine bay, injectors and pressure regulator, fuel pump are good. . I noticed my TPS voltage is only 3,5v at WOT. (Tps is set correctly at 0,54v) . New tps is doing the sam thing (only 3,5v at WOT). Could it be the reason of lost power? What to check next regarding to low WOT TPS Voltage?? Manual is saying that TPS WOT should be around 5v at WOT.... and there is no error codes.. Thx for any help and goood advice

 

Unplug the tps connector koeo what’s the grey wire voltage ?

 

I replaced the TPS Connector. I have good ground, 5v and not damaged signal wire. Tps is new. When i removed TPS from Throttle Body i can push TPS by hand more than i can with Throttle Body and then i have 4,8v. But when i set TPS to 0,54v i have at WOT 3,5v. When i set TPS Higher (about 1,1v) then throttle body is pushing it at WOT to 4,8v. I am wondering what is the problem that normaly i can't get 0,54 at closed and 4,8 (or even over4) at WOT. My friend is telling me that i have the correct Throttle body for adjustable TPS. And a veryfited that Throttle body can open and close all the way. Should i mess with the idle screw to back it all the way? it is in original position from dealer. Here is the movie how it looks.
https://youtu.be/5emr-W4Q134 it is not .54 but it showcase the problem.

 

Not sure this is your problem, but many times the back hole, I believe, needs to be ground out (enlarged)/slotted) to properly position the TPS. Play around with the positioning and and it should be obvious what needs to be done. But regardless, the voltage is only used for 2 things:
1) Err 21 & 22 tests (at 3.5v you're OK)
2) Idle considerations by the code at < 0.78v. So never set 0% at > 0.78v. Anything 0.54-0.65v OK.
If enlarging the hole(s) does not fix the issue and 3.5v is the max, then need to ensure that throttle blades are 100% open at fully depressed pedal. The only tuning adjustment that may be needed is the PE TPS% table because at 3.5V, you will only see about 70% 84%TPS at WOT. Will need to adjust TPS% PE invocation table accordingly.
If you use TunerPro, the attached ADX at key on, engine off can be useful to see what's going on at 0% and WOT.

Also, if the throttle blades are fully open at WOT, the issue of power loss is not the TPS. I'd look to pump or injectors, especially if factory Multecs and even if they are providing the proper range of hot and cold resistance. By what measure are you sure both are "good"?

With Factory Calibration values used to compute TPS%, >= 4.0v will result in TPS%=100.

 

Hi. Today i have noticed 2 problems . 1st. is that some "fcked up" "Mechanic" that was working on this car before i bought it .... bend my old tps leg and throttle body plate (near regulation screw). This car had idling problem so he bend it to increaser RPM and bend tps to increase tps voltage !!!! LOL. (I fixed idling problems by replacnig IAC and cleaniong throttle body and instaling new gasket). Look at the picture 1 (my) and picture 2 (from internet)

Throttle body bent
. There is my 0,3v loss of voltage (on WOT i can push TPS a little bit more by hand).
And 2 problem is shown on this movie. When i disconnected Tps signal wire (BLUE - to ecm) the voltage raised by 0,5v. And on the movie i can get 4,0v at WOT and 4,36 (by hand). Sooo i am confused about that. I have checked the voltage by disconnecting ecm pin from harness and measure voltage that ecm is getting to exclude bad wires. And the voltage is the same. 4.0 and 4,36 by hand push TPS. So tomorrow i will bend back throttle body plate to get 0,3v more and regulate TPS. But what about 0,5v loss of voltage when TPS signal wire is connected to ECM??? TPS and connector is good and the wire is ok. (I replaced it too with new one). This is 2nd Ecm in this car (1st was damaged when i bought it) What next? Another ECM?

 

As said before, would not worry about it. As long as the TB blades are 100% open and the ECM is seeing >=4.0v you're OK (not voltage from your DVM but also from a log to see what the ECM is seeing).

 

TB Blades are open 100% . Sory i forgot to mention that yesterday my friend checked it with scanner and scaner connected to obd port was telling us 0,3v on closed TB and 1,5v at WOT. About a month ago another friend with laptop was chcecking this car and then he saw the logs and he told me to replace my TPS sensor becouse ecm was seeing 0,3 v (closed) and voltage was climbing to 1,5v and not going more. That is why i replaced TPS with new one and i was chcecking the connection to computer and even make a new wire directly to ECM. And ecm when connected is not geting 4v. When signal wire is connected to ECM multimeres says 3,5v at WOT. This 4v reading at WOT i was getting only when Tps signal wire was unpluged from ECM Harness. That is strange. Even my buddy was shocked and he works on those cars and had no idea what is happening. I have someone that is called "3gen and comp magician" but he don;t have time to look in to this so for the moment i am stuck. Do you have any other ideas?

 

This all appears to be rooted in the assumption that the replacement TPS is actually good (linearity).

Also absent from your notes is whether the TB minimum air position has been set properly and whether the TB shaft is worn.

 

Good points!

 

I have checked with 3rd Tps that is from car that have known good Tps Voltage. And when i instaied 3rd tps( it is 100% good ) in my car it has no diffreance. Still getting only 3.6v at Wot. So maybe my throttle body is gone. Shaft has some play and when i chcecked it i saw that someone was messing with it as shown on the picture. It seams that someone was welding it maybe. ?.

Now i am waiting for new known throttle body to chceck if this is the problem. I will report in few days. Thx for good advice.

 

That is suspicious. The bellcrank is almost always staked to the throttle shaft, not welded.

 

Today i got new throttle body. And it did not improve WOT Voltage. Still 3,6 at WOT. New Tb is in great condition so i will keep it. But that problem is still not resolved. If it is not TB, TPS, TPS connector, Signal wire, then what it could be? Bad ECM ? hm... my mechanic that is good in 3 gen computers is unavailable i am thinking about buying cable and testing what computers is seing. What cable and program do you recomend? Can you send me a link from ebay ?