Throttle Position Sensor

[scottxd45]

I just started having an issue with my '89 efi. It starts up and idles fine but if I open the throttle much more than a crack it stutters really bad. I can drive it still as long as I don't open the throttle too much. I immediately thought it was the TPS just because it was throttle position dependent. I don't know the proper testing procedure though and I could find it by searching. It has 5 volts to the upper pin so that's good. I had less than 1 ohm between the bottom two pins at closed throttle OFL at anything more than that. Does that mean bad sensor?

[scottxd45]

Also I get full battery voltage to the bottom pin when I open the throttle. That doesn't make sense to me.

[Team Lightning]

That sounds like my ex's Nova when the fuel filter clogged up. Have you filled it up at a different station than where you normally get fuel?

[william]

Sounds like fuel filter to me to.
At least a place to start.
Cheap and if you haven't changed it lately it needs one any ways.

[scottxd45]

I just bought the car so I don't know when it was changed last I'm going to get one right now.

While trying to remove the fuel filter I broke a nipple off of something on the firewall with two vacuum hoses going out of it. Uhgg


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[william]

Sounds like your charcoal canister it filters the fumes that come from the gas tank it's an emissions thing mines no longer hooked up. You really don't need it.

[scottxd45]

Good to know. Did you unplug it or just cap it off?


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[william]

I pulled the main hose coming from under the car. Black hose with red strip I believe. Then I put threw the hole in the inner finder. You don't want to cap this because it let's off gas fumes from the tank would want it to over presser the tank.
I the removed the vac lines from the solenoid and caped em. Also unplug it. Because it will sit there and click trying to purge.

But I'm not running a b3 so it may be slightly different.
On the motor side.

[scottxd45]

Ok I wasn't able to get a fuel filter tonight. I did blow through it and it seemed fine so I put it back on so I can drive it to work tomorrow.

Can anyone give me the ohm reading I should be getting at which pins on the TPS? I'm still thinking it is the culprit.

[bravekozak]

1E Y/BK idle
2G Y wide open throttle
2C Y/GN signal return (middle pin)

idle and WOT have two different voltage ranges depending on driving condition.

Voltage can range from 0-12V

At a cold start with cold air, fast idle is 0-1.5V while WOT is 10-12V

[scottxd45]

I guess I don't understand how it works. I thought 5 volts was sent to the sensor and then I thought the sensor was a variable resister sending a lower voltage reading back, indicating the position.


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[scottxd45]

How does temperature effect a tps?


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[Team Lightning]

My understanding of the Festiva TPS is,that it's more of an on-off switch than a variable resistance unit.

[bravekozak]

The return (middle pin) is spliced to the engine coolant temperature sensor and the VAF. A lot has to do with whether the coolant temperature is below or above 17 degrees C.

[scottxd45]

Wow ok. So spell it out to me how to check this thing. How do I know if it's bad?


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