Have a bit of a problem:

I have a 1994 Sentra LE with a 1.6 litre engine. Have replaced the spark plugs, plug wires, distributor cap, rotor button, and the front fuel filter next to the firewall under the hood with no affect to this stalling problem I'm having. I'm getting a weird stalling issue when the car is idling, especially when I'm slowing down for a stop light or stop sign, or am going around a turn. When letting it idle with the hood up, there are times the rpm's will go up and down, making a whirring noise, almost like the car is getting bursts of fuel. Then I'll pull the throttle, let it idle, and it will idle fine until I go driving down the road and it seems to start over. Any ideas? Having someone double check my spark plug installation to make sure they're spaced correctly and I didn't accidentally cross-thread them, but it was doing pretty much the same thing before hand. Seems to be becoming more frequent recently though.

The person I bought the car from had to drill a hole in the float basket the fuel pump sits in to get fuel pumping properly. He did not see anything wrong with the fuel pump itself and couldnt find a reason fuel wasnt getting through to the pump, and drilled the hole. I posted another thread on this awhile back and got a response that it shouldn't be a problem, especially since the filters should catch any debris, but am starting to wonder.

Any input is greatly appreciated. Thanks in advance!

check for vaccum leaks primarily on your brake booster hose and your PCV valve hose. If those are ok it might be your IAC valve struggling to maintain an idle.

Hey,

I'm trying to figure out the correct voltage settings from the TPS. I have checked the TPS and the voltage settings actually read backwards. I'm wondering if the Haynes manual I'm using has a misprint.

what do you mean backwards?

I have the positive probe connected to the red signal wire, the bottom wire when the connector to the TPS is plugged in, and from what I can determine the center white wire is the ground, while the top white wire is the wire you're supposed to test with when testing the voltage from the ECM to the connector. The manual says the voltage is supposed to be ~0.5v at closed throttle (when testing the actual voltage to the TPS, not to the ECM) and that it's supposed to read ~4.5V at full throttle. I'm getting the exact opposite of that, 0.5 at full, and 4.5 or so at closed. From what I remember, the voltage to the ECM itself read as the manual says it's supposed to.

ok your wires on your tps and most other sensors on the car are as follows one outside wire is power and the other is ground. the center is almost always your signal to the ECM. You should have ref or battery voltage on the hot wire and 0V [or less then .02v] on your ground wire if those to checks are good then you check your center wire at idle and at full throttle. it should read .5v approx. at idle and 4.5v approx at WOT.

Ok,

From what we've tested, the probes seem to be backwards from what you've described, if you're looking at the TPS while plugged in it seems to be as follows:

Top/-\|W| - White ECM Signal Wire|W| - White Ground Wire|R| - Red Power Wire\_/Bottom

Any suggestions? Please clarify your previous explanation of which probes to test for the voltage readings if possible. Much obliged.

I am going to have to pull up the factory service manual on it tomorrow and see what it says for wire orientation and if possible I will copy it.

Ok,

I did some more testing tonight with a friend.

We had the positive terminal of the voltage meter plugged into the bottom red signal wire, and the negative terminal into the center, seemingly ground wire. The voltage reads ~4.5v at closed throttle and ~0.5v at WOT. My friend is pretty sure the problem isn't with the actual sensor itself, as he unplugged it and the stalling problem is still occuring. The car's idle is really random, and stalls if you let off the throttle/gas pedal quickly.

I found out that the friend I bought it from apparently had to put some wires back in place and tape some up when working on the car before I bought it. Is it possible two wires could be backwards, which is why the voltage is reading backwards from the manual specs?

possibly but I need to pull the info from the FSM today and be 100%sure on how your wires are suppose to be. I will get back to you tonight on it.

thank you!

ok It is as I statedand your wire colors are wrong you should have one that is gray in color not white so clean the wires and look at them closely it should be GY,W,R from top to bottom as you have it layed out above. The middle wire [white] is your signal wire. check its operation by placing your black lead of your volt meter on the negetive battery terminal and the red lead on the middle wire of the sensor.

I also took a look at some stalling/ no start issues with the sentra that year and it seems there were a few issues with the fuel pressure either the fuel pump it self or a connecion in the wiring. Both issues cam up in seperate incidents.

Took it to the local Nissan dealership and had it diagnosed. They said it's my Mass Airflow Sensor (MAF?). Joy.