1992 3.1 Lumina turns over, then dies

[Korey817]

Alright i have just changed out the Throttle Postion Sensor as per the code it gave to no avail. The car turns over, then runs for a minute or two, then its like im giving gas and surges and then dies. Its like a wave its RPMs will go up down then up then it dies. What could it be the MAP or a Vaccum line? 

[cutty collector]

I would put a fuel pressure gauge on it check for a major vacuum leak or stuck egr valve

[Imp558]

Welcome to the forum, fuel pressure X2.

[Korey817]

Alright i did the fuel pressure and at idle i got 35 psi and when i upped the rpm's it never went above 40. 

Also tested the fuel pressure when I don't start the car but turn the key I got 45 at first then it bled all the way down to 10 fairly quickly like within 30 seconds.

[Imp558]

That's low fuel pressure.. Now you need to figure out if it's going somewhere like a bad regulator, having trouble with a plugged fuel filter, or a bad fuel pump. You should be 40 at idle up to 45 or 47 running with the throttle cracked.

[Nas Escobar]

I'd suspect the fuel pump and the fuel pressure regulator. I'd diagnose the fuel pressure regulator first since it's easier to get to and cheaper to replace. There's a vacuum line connected to the FPR. Disconnect it and if fuel leaks out, that's your problem. If not, I'd suspect the fuel pump.

[Schurkey]

...or the hose (or damper, depending on how the vehicle is equipped) between the pump and the steel tubing of the hanger.  Hose or damper diaphragm can rupture, lowers fuel pressure and can cause the fuel pressure to bleed off.

 

'Course, if you have to drop the tank to change the hose, you might as well stuff a pump in there, too.

 

 

 

 

 

 

For the record, I don't diagnose fuel pumps without checking the pressure, voltage, and the amperage draw.  Voltage must be tested as close to the fuel pump as practical.  Current testing can be done anywhere in the circuit--such as removing the fuel pump fuse so that the leads for the ammeter can be slid into the fuse socket.  AT MINIMUM I'd use the ammeter function of a multimeter.  Most of them will accept a 10-amp draw.  The fuel pump shouldn't take more than 7 amps.

 

Better is to use an inductive current probe and an oscilloscope.  Using the pattern on the 'scope, you can tell current draw for EACH BAR of the fuel pump motor's armature, and you can determine pump RPM.

 

If you can verify voltage to the pump, current draw of the pump, RPM of the pump motor, fuel pressure and fuel volume...there's very little guessing left.