Engine hesitated and how I fixed it, 1998 Corolla

[Anthony1]

My girlfriend had this strange problem with her 1998 Corolla. The engine would hesitate just for a second. It happened while driving through town and on the highway. It seemed completely random.

She took it to her local mechanic. He hooked up his code reader; there were no codes and that was all he knew how to do.

We used fuel injector cleaner for three tanks of petrol; that didn't do a thing. Then I was thinking maybe the fuel filter was clogged, but an auto parts clerk told me the fuel filter very rarely gets clogged.

So I read through the forums and pieced together bits of information with a bit of conjecture and decided the problem was probably the throttle position sensor. That was it! I tested it the old fashioned way. I stuck a pin through each wire and read the voltage with my multimeter while Burgen pushed on the accelerator. If you have the same situation, I can post specifics for you.

The throttle position sensor is just a variable linear resistor. Oh, one of those, you say. Think of the volume knob on a stereo. That's also a variable linear resistor. It changes the volume (it's variable), and the volume changes gradually (that's the linear part). The volume doesn't suddenly jump from soft to super loud.

The throttle position sensor tells the computer how much you are pressing on the accelerator. Then the computer uses that information to adjust how much petrol it squirts into each cylinder. If your engine is hesitating because the throttle position sensor has failed and you unhook its connector, your hesitation problem will go away. But your check engine light will suddenly turn on. And without the accelerator information, the computer has to guess where the accelerator is. Sooner or later it will guess wrong. You will try to start your Toyota but it won't start because the engine is flooded. Then you have to wait half a day or a whole day for the extra fuel to evaporate. Yes, we did this. Live and learn. At least that happened on a Saturday.

Burgen ordered a new throttle position sensor for 36 dollars. The engine runs smoothly now so it was money well spent.

[rezzle]

Glad to hear you fixed it.

Good detective work.

[SR5_4WD]

I never knew you could flood a fuel injected car. Better yet I dont want to see if its possible

[T-Comm]

taking the plugs out of the cylinders if it's flooded will get you back on the road quicker.

[JZ TWINS]

I am suprised his scan tool couldnt tell the tps was bad.

[radarguy]

Just a quick clarification. The volume control on your stereo is not linear. It is what is called an audio taper. Otherwise great analogy.

[falnfenix]

Originally Posted by SR5_4WD

I never knew you could flood a fuel injected car. Better yet I dont want to see if its possible

absolutely. a friend of mine flooded his brother's Mazda back in '98. it was a 1997, and was fuel injected.

[REN69]

Originally Posted by radarguy

Just a quick clarification. The volume control on your stereo is not linear. It is what is called an audio taper. Otherwise great analogy.

WTF does volume control have to do with this thread????

[wheredoesthisgo]

Just a tip from an electronics tech. Probe the connector with a paper clip next time. You just opened up a source for an arc.