94 Mustang gt 5.0 running with tps unplugged

MarshallPhil3 · Sep 27, 2011

i bought the car from a guy and he told me the tps was bad in it so he's been driving with it unplugged. it was driving fine until it started sputtering and losing power then it would get it back and kind of jerk. It felt kinda like it wasnt getting fuel so i replaced the fuel filter and it wasnt that. now im in the process of cleaning the TB and MAF. anyone have any ideas about what it could be. thanks

Canary94GT · Sep 27, 2011

it sputters, loses power and jerks with the tps connected or disconnected?

MarshallPhil3 · Sep 27, 2011

With it disconnected, but its been diconnected for a while and it just now started to sputter, jerk, lose power. Would it go from driving fine to next day little sputter, no power, jerk bc the tps sensor?

Canary94GT · Sep 27, 2011

that definitely could be, and probably is, causing the issue.

If your throttle position sensor is still there, try reconnecting it and see what happens.

If you're still having problems, pull codes from the computer by running a self-test and write them down: Checking your Ford Mustang computer codes. You should probably do this anyway regardless if you're still having problems or not. It will tell you if you have other problems.

You'll probably get a code saying something is wrong with the throttle position sensor, regardless if it is bad or not, since it was disconnected for so long. So if you do, I'd reset the computer then take a 2-5 mile drive (with the tps connected if you can) and check the codes again to see if it's still your throttle position sensor.

To reset the codes on the computer, follow the procedures to perform a KOEO (key on engine off) test (in link above), then remove the jumper wire from the self-test connector when the dash starts displaying the codes.

All of this is also described in a 1994 mustang Haynes repair manual which would be a very good thing to purchase.

Canary94GT · Sep 27, 2011

oops double post, sorry

MarshallPhil3 · Sep 27, 2011

Okay thanks, i just cleaned the Tb and put it back on and its still doing it. it wont rev above 3000rpms and will barely go like if im out of gas. Ill pull the codes and go from there. thanks

BIGDATOWN · Sep 27, 2011

How about fix the tps? Kind of hard to diagnose a problem with a already known issue. With the tps unplugged the computer will not add fuel as needed. The tps is one of the most important sensors on the car!

Canary94GT · Sep 27, 2011

could be his tps isn't bad and the previous owner misdiagnosed it, that's why it's worth pulling codes first so he doesn't just go throwing parts at it

BIGDATOWN · Sep 27, 2011

I agree^^!!

toyman · Sep 27, 2011

Canary94GT said:
could be his tps isn't bad and the previous owner misdiagnosed it, that's why it's worth pulling codes first so he doesn't just go throwing parts at it

Okay, but it's really easy to test the TPS with a DMM without even considering running codes (that should be done of course to see if other sensors may be at issue). Back probe the signal wire from the TPS. In the closed position it should read about 1v. As the throttle is opened the voltage should increase smoothly to about 4.7v at WOT. As mentioned the TPS is a critical sensor and needs to be functioning properly.

MarshallPhil3 · Sep 27, 2011

okay ill change it tomorrow. Should i diconnect my battery so it'll reset the kam since its been running/learning with no sensor?? Also could me running with no tps cause other sensor's and stuff to default?

MarshallPhil3 · Sep 27, 2011

Also i pulled the codes and i got 122, 553 the 122 is the tps low voltage, so should i plug it back up and check the voltage before replacing? thanks

Canary94GT · Sep 28, 2011

yeah just check your voltage to it as toyman described

553 should be related to the smog pump system i believe. I read that it shouldn't really cause issues like yours, but thats not guaranteed since im not sure exactly what that code means

toyman · Sep 28, 2011

Actually it's part of the EGR system.

Canary94GT · Sep 28, 2011

that is a vacuum diagram which is just saying that the aird and airb valves get their vacuum source from the same place as the egr valve

the aird valve is the air diverter valve which diverts exhaust gases from the catalytic converters to the heads, part of the smog system

btw cool desktop skin

MarshallPhil3 · Sep 28, 2011

would that vaccum am1/tad cause the problems im having with my car.

MarshallPhil3 · Sep 28, 2011

Would my fuel pressure have to do with it? If so how do i check it and adjust it cause i dont know how to. thanks

Canary94GT · Sep 28, 2011

Have you tested your throttle position sensor yet as toyman described? That is the first thing I'd do before moving onto other tests, especially if you don't have the tools as described below.

To test fuel pressure, you need a fuel pressure tester gauge, and to test vacuum, you need a vacuum testing gauge. Both you can get at a local auto parts store or places like Sears. Also the Haynes manual would help A LOT! Because it goes through all these procedures (checking fuel pressure, checking vacuum, etc) in a detailed manner with most of the time a better job than we can/want to in a single post

But the first ticket is to obtain those gauges. Most of the time you can find out how to do the tests by searching the internet, or if you really want we can describe them.

MarshallPhil3 · Sep 29, 2011

No not yet, i was looking for my DMM but i couldnt find it. also i dont have the really sharp piercing sticks any ideas of how i can get into the wire. And im confused i dont see how one day it was running fine then the next day a little bad and the next day really bad. Thats why i was thinking FPR or FP.

Canary94GT · Sep 29, 2011

Well it shouldn't run correctly without a TPS anyway. So the fact it supposedly did is strange, and the fact it suddenly became worse is stranger, but honestly the first thing to do is test the TPS if u can or if you really want to you can "throw" a part at it and get a new one. But there's a definite possibility the previous owner misdiagnosed the TPS as being bad.

I've never back-probed a sensor before, but you can probably do it by sticking really any piece of metal into the back of the connector, such as a nail or needle I think? and then read the voltage coming from the piece of metal. Again, I've never tried it before but I think this is how you do it. Of course try not to damage the connector.

Edit: Actually yeah, you can also buy back-probe kits like this:

But a needle, paperclip, or some sort of pin should work. Hmm I should really try back-probing some of my sensors and see what it tells me :o

The Haynes manual outlines how to test all of the sensors/connectors btw.

94 Mustang gt 5.0 running with tps unplugged

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