Which sensor to buy?

[TazMan]

Okay guys I have a 92 Grand Prix 3.1l that needs 2 sensors, a TPS and a MAP sensor. Now I’m a little tight on money this week and can only get one till next check. The two failed sensors cause the car to hesitate and usually stall if I don't stomp the pedal down, whenever I try to pull from a stop. Since I’m still using this car to get around, I was hoping some of you many knowledgeable people out there can advise me on which sensor would be better to get as far as helping performance till I can get the other one next week. Thanks everyone for reading.

[NeonKnight]

get the TPS, it should stop it from stalling at a light.

[bszopi]

Or, you could possibly go to a junkyard and pick up both for less than a single new one. Just a thought...

I'd say its kind of a toss-up, but yeah... I'd probably go with the TPS as well.

[tractorman]

How do you know they're both bad? I've had a bad TPS make the computer THINK that the MAP sensor was also bad. I'd probably start with the TPS and see if it resets the code(if that's what you're going by).

[TazMan]

Thanks again everyone. I’ll go with the TPS if I don’t go the junkyard route. As far as the MAP sensor actually being bad, I don’t know how accurate of a test this is but I read somewhere that the voltage in should be 5 volts and the signal voltage out to the computer should fluctuate from 0-5 volts as vacuum changes from high to low. When I probed the harness with a meter I got the 5 volts in, but the signal voltage out stayed steady around 1.1 - 1.2 till WOT where it would jump to 4.5. I also get code 34 which my Haynes book says means the MAP Sensors signal voltage is to low. It idles real slow and quiet so I don’t think I have any vacuum leaks. As far as the junkyard goes, since these sensors were okay before the car sat for 11 months, I figured there’d be a good chance of me getting more bad sensors there. Do you guys have good luck with sensors like this from the junkyard?

[Rhedalert]

grab sensors from cars that appeared to be running fine before being junked, such as wrecked cars with relatively low mileage. I've never had an issue, except once when I grabbed a bad EGR, that messed a lot of things up.

[TazMan]

The junkyards around here use to let you go out and pick what you need, but as of the past year or so they don't anymore. They say insurance reasons. Now they just bring you the part and it's usually already been removed from the vehicle. I've been a little leary of getting certain things since they started doing that.

[TazMan]

Put in the TPS this morning in the AutoZone parking lot. The stalling completely disappeared. I haven't checked for codes yet but I still have the "check engine" light. The car feels slow and will still stumble occasionally on the highway while accelerating, kinda like it's suddenly not getting gas, but this only lasts a few seconds and hopefully the MAP sensor will fix that (assuming the code left thats causing the "check engine" light is still the MAP sensor). I can finally use my air conditioner and drive the car without frustration! Thanks again everyone. As soon as I can get the MAP sensor I'll post the results for anyone else having similar problems.

[TazMan]

Stumbling on the highway was from a bad ignition module that didn't throw a code till late. Replaced Ignition module and MAP sensor and the cars been runing great. Thanks for all your help.