'97 stumbles while idling

[pony-up]

i have a problem that has gotten progressively worse. it began as an occasional stumble at idle, which got more frequent, then one day stalled. i learned that i could "reset" the throttle by tapping it briefly to the floor, and the idle will smooth out for a few minutes. i had the induction off trying to trouble shoot, when i heard a choking hiss coming from the un-filtered induction tube. seems as if the ecu is choking the engine by closing the throttle.

does this sound like a possible throttle position sensor problem? it seems like the tps may be telling the ecu that the throttle is open wider than it is, and the ecu is sending a command in response, telling the throttle to close more. whatever the cause, the throttle is clearly closing while at idle. does anyone know how to check the tps? or maybe had this problem?

 

[jlkuehl]

I had a similar problem on a full size truck, and a quick spray with some throttle body cleaner following the directions on the can cleared it right up. At $3 a can, it's worth a try, if it doesn't work, you aren't out much, and have a nice clean throttle body to boot.

The hissing sucking sound is normal at idle with the air intake tube off, the engine is drawing air through a throttle butterfly that is almost closing off all the flow.

The TPS is easy to check, remove the harness connector from it, hook up a multimeter to the exposed pins on the sensor, work the throttle and watch for a smooth even change in the resistance. I'd still start out with the throttle body cleaner, though.