TPS woes!!!! help!

[ninety15.0]

I have been having this rediculous problem with my stang for a long time now and i still cant figure it out. Im pretty sure the problem is centered around the throttle position sensor or throttle body, because when i floor the car it actually accelerates much slower then when im at 3/4 throttle!!!!!!!!. my poor car only went 15.2 at around 94 mph. So I went to the parts store to replace it and the guy said there were two possible sensors for a 91 and i needed the original tps to read the numbers off it. well the sensor that was on there was off my mechanics 351, and it had no numbers written on it. so i just bought the tps sensor that autozone had in stock. well my car is still having the problem. The TPS thats on there now has no real adjustment room.... anyone with any information about this problem or who has experienced anything like this, advice would be awesome. right now my pony is LAME!!! 15.2 WTF!!!!!!!!

 

[TheUser]

You can drill the holes in your tps out for adjustment room...i've done it and so have many others, just go a little at a time. People say you need to get below 1.00, but I've read as long as you're between like .6 and 1.5 or so, you're cool and that's from Probst, so who knows. All I know is that it should be at or around 5 volts at WOT.

Maybe your fuel pressure isn't set properly...what do you have it set at vac off?

 

[ninety15.0]

yea thanx i have heard that too, but i didnt wanna try it until i was sure. I was messing around with my FP lately because it hasnt been runnin right. I think right now its at ~42/43 psi. vac off. I have a guage right there on the rail so i can always change it real quick. Is that too much....?

 

[TheUser]

if it's too much pressure, the computer would prob. just shorten the pulse widths to make it how it should be, but stock is 38 vac off, so you might start there. You might consider backing the timing down a little bit or check it to make sure it's not off. Wouldn't hurt to try it if the TPS mod or fuel pressure doesn't fix it.

 

[HISSIN50]

the EEC puter can adapt +/- 25%. so i would not leave it over 1.25 volts base setting (puter wont be able to adapt it down far enough).

one can hog out one hole on the TPS to make it adjustable. have you checked for a nice clean sweep (on DMM) and proper voltage and ground to it?

what codes are you spewing?

good luck.

 

[ninety15.0]

well i had the FP set even a little higher before because the car seemed to be running better in the lower rpms...but i would get the CE light because it was runnin rich....and you could really smell it outside the car...so i turned it back down. I havent checked the voltage sweep with this sensor yet but i have done it in the past. i need to check for codes...b/c i do get the CE light when the car is run for a long time...like more than 30 minutes. I could still be rich? thanx for the advice, i will do some testing after classes today.

 

[HISSIN50]

well i had the FP set even a little higher before because the car seemed to be running better in the lower rpms...but i would get the CE light because it was runnin rich....and you could really smell it outside the car...so i turned it back down. I havent checked the voltage sweep with this sensor yet but i have done it in the past. i need to check for codes...b/c i do get the CE light when the car is run for a long time...like more than 30 minutes. I could still be rich? thanx for the advice, i will do some testing after classes today.

remember the puter is adaptive. you could turn the fp whereever you want (within reason and the parameters i listed above) - the puter will adjust the injector pulsewidth to trim the mixture.
EDIT: The User already said that. he is right.

ummm, well what is the code(s) that is/are being tossed? that is where i woulda' started. good luck.

 

[jrichker]

Dump the codes and see what the computer says is wrong…

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
OR
See http://www.dalidesign.com/hbook/eectest.html for more descriptive help
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Walmart.

 

[VG30DE]

2 Things I'd try...

1- Reduce the fuel pressure.
2- Advance the timing.

Too much fuel pressure and/or too large of injectors will create the symptoms that you describe. After about 3500 RPM, the computer's ability to compensate for a rich situation is decreased because of the higher demand on the motor and the longer length of injector pulse associated with the higher engine load. Advancing the ignition timing raises cylinder pressure and temperature and therefore is capable of burning a larger amount of fuel per combustion cycle than if the timing were at stock or close to it. Throttle position problems usually are a glitch where the sensor drops out of range or zeros out altogether and usually a sharp power loss or gain can be created by slight movements in and out of the dead zone in the sensor. Also bucking and hesitation can be common with a bad TPS, and it doesnt sound like this is your problem. Hope this helps...

 

[ninety15.0]

vg3ode, thanks for all the info that was very helpful. I have a couple questions however. I am already running 14* advance and im wondering if i should try to go any higher than that. how much advance can i saftely get away with before pinging? Jrichker, you seem like a wiring/computer genius...thanks for the help. I messed with the tps and tb yesterday and i could not get enough adjustment out of the TPS to get the baseline voltage about .58 volts. I know thats low its supposed to be between .94 and 1 volt correct? so i think i need to drill the mounting holes on the sensor untill i can achieve the proper voltage setting. i will pull codes when i get a chance to work on the car next!! thanx a lot for the help fellas!

 

[04sleeper]

I have always used .980 volts for my TPS and it has always worked good for me.

 

[VG30DE]

Yup, definately need the voltage to be about .96-.98 or the computer doesnt like it at all.
Different cars like different amounts of timing advance for a lot of reasons. Factors like engine conditoin (compression), timing chain stretch, mass air calibration, TPS setting, which PCM you have, and what brand and octane fuel you run will all affect how much base timing you can run. I'd get the TPS issue cleared up first before going crazy with the timing, but once you get that under control, and you make sure to run a quality 93 octane fuel, try going up to 16 to start and make some WOT runs getting on the highway or on a long stretch so you can listen to the motor with high load in the higher gears. Any spuddering, pinging, or even slight detonation is an indication that you've advanced the timing too far and you should pull a degree or 2 at a time until it stops. That's the old fashioned way of timing by ear when you dont have a dyno or track readily available to show any actual results. Advance it as far as you can, and then back it off a couple degrees and thats the best you can do without dyno tuning.

 

[Daggar]

Anyone can answer this: It's a 91 so I'm assuming MAF correct?

 

[jrichker]

Anyone can answer this: It's a 91 so I'm assuming MAF correct?

All 89-93 Mustangs are Mass Air, the 88 Cali models were supposed to be Mass Air also.

Speaking of Mass Air, have you cleaned the MAF element?
The MAF element is secured by 2 screws & has 1 wiring connector. To clean the element, remove it from the MAF housing and spray it down with electronic parts cleaner or non-inflammable brake parts cleaner (same stuff in a bigger can and cheaper too). This can help the lean running condition at normal fuel pressure and poor throttle responce, plus it is cheap and easy to do.