TPS upgrades? effects?

[Turdle]

Of course the accelerator pump on a carburetor is mechanical, and yes, it squirts a small amount of fuel into the intake when you initially step on the gas. You can customize the accelerator pumps fuel curve (amount of fuel and length of time to deliver) by changing the pump cam, pump lever, pump lever pivot point, fuel discharge nozzles, etc. Fortunately, the TPS replaced all this.

On an electronic fuel injection system, the computer uses the voltage from the TPS to calculate all the things you listed. But then what does it do with the information? Usually nothing, it almost always ignores it! However, if the computer decides the TPS voltage means you just stepped on the gas it briefly overrides the normal fuel curve and adds more fuel, by temporarily changing the injector pulse, so the engine will not bog. That is why I said in the original post, the TPS is the modern electronic equivalent of an accelerator pump.

The only other TPS function is to indicate a closed throttle or WOT condition. In either case, the computer then reverts to preset fuel curves until the TPS signal changes.

Your post did not list an alternative purpose for the TPS. If I am wrong and it does not replace the accelerator pump, what does the computer do with the signal? Why does the system need a TPS?

Umm, kinda--
however the signal is used for many things-including the transmission.

 

[Space Truckin']

True, some electronic transmissions do monitor the TPS to help determine shift strategies, etc. I overlooked this because I focused on engine functions.

 

[gijoecam]

Stating that the TPS replaces the accelerator pump is like saying the fuel injector replaces the carbeurator... it's like comparing apples to pizza. They're not even close to being the *same* thing... they are both completely different items that have some overlapping functions/duties. To call it a replacement implies (in my mind anyways) that you could take a vehicle with an accelerator pump and replace it with a TPS and have it run: That's just not the case.

Splitting hairs either way... It's a moot point.

-Joe

 

[CDW6212R]

It's an odd concept but no big deal, next subject.

 

[Four0Sport]

they make pizzas with apples on them, if it matters. j/j

 

[Space Truckin']

To call it a replacement implies (in my mind anyways) that you could take a vehicle with an accelerator pump and replace it with a TPS and have it run: That's just not the case. -Joe

Wow! That is not at all how I intended you to interpret what I said. They are clearly not directly compatible replacements that can be interchanged. I don’t know why you read that into what I said but now I understand why you objected. Thanks for clearing it up. My original point was, as you confirmed in your last post, they serve the same basic function. I completely agree that they accomplish this in vastly different ways. Your original summary below the shop manual information you supplied was quite good as far as it went. My post was intended to supplement yours, not contradict it.

I’m not saying anyone did it in this thread but my whole reason for commenting on the subject is that throughout this forum, and many others, the TPS is consistently blamed for problems it does not, and sometimes could not, cause. This seems to happen because many people do not understand its function or operation. Diagnosing incorrect operation is much easier if you begin with understanding correct operation. The forum is filled with posts from people saying, “I just replaced the TPS and I still have the same problem.” Oxygen sensors and the IAC are just as bad. AutoZone is laughing all the way to the bank with money people spend on unnecessary replacement of these parts.

Maybe that could be our next subject in the stock forum. What are the top five or ten most common unnecessarily replaced parts? How do you avoid these costly mistakes? Some basic automotive systems theory of operation and troubleshooting techniques, supplied by knowledgeable forum members, are all it would take to create a very helpful thread.

 

[CDW6212R]

There's a good idea.

 

[sbkold]

Umm, kinda--
however the signal is used for many things-including the transmission.

Im having a TPREL issue with my 97 5.0 X.

My Scan tool never indicates Closed Throttle. Always Part Throttle. Even when engine is running and trans is shifting properly.

Intermittently the TPREL value goes to 0 and then trans shifts are delayed to the point of violent shifts. Also engine idles high.

My TPS value is always a steady 0.97-0.96 when idling. Never varies. Of course value changes when applying throttle.

The TPREL value stays at 0.75 which is why im not showing closed throttle im sure.

Hoping someone can chime in and help me figure out what going on to make TPREL value so low.

Thanks in advance guys.

 

[2000StreetRod]

TPSabs vs TPSrel

On my Sport TPS absolute varies between about 20% for closed throttle and 90% for WOT. I suspect your scanner is reading TPS absolute instead of TPS relative. The PCM at ignition ON and periodically checks the TPS output for a new low value. If it finds one then it establishes the new low as closed throttle. If your scanner is reading TPS absolute and it displays 0 then there may be a problem (dropout) with your TPS between closed throttle and WOT. You could have a loose connection or a bad spot in the variable resistance. You may want to perform my TPS Test Procedure If you're using a digital ohmmeter move the throttle plate slowly because the meter only samples periodically.

 

[sbkold]

Thank you for your response.

Im not sure the difference between TPSrel and TPSabsolute.

My Scan tool (snap-on MT2500) shows real time Volts for the TPS.

Ive checked this PID often and never seen any voltage below 0.96.

The TPSrel PID did show 0.0v when vehicle was running poorly.

Ive driven some today and I did notice TPSrel did go to 0.95 although I never saw TPS voltage drop that low.

Ive looked for any chafed wires - they all appear perfect.

Im still trying to learn and see what could be causing this issue. Thanks guys.