QuestionThe car starts to stall when excellerating. There is no pick up either when coming out of a stop or going up a hill. Overall, the drive can be very jerky with little power to the engine. I need some help.
Thank you very much
Angel
AnswerHello Angel,
My first suggestion would be to check the fuel pressure. The injection system requires that the pressure and volume be at a certain value, since the injectors do not add any pressure when working. They are just glorified solenoid valves that open when told to by the ECM, and all the injection is done by the pressure supplied by the pump.
If that fuel doesn't get there under the correct pressure, it could be a restricted filter, which is along the frame, in the fuel line, a pressure regulator wide open, allowing all the fuel to return to the tank, thus not building proper pressure, or a leak in the fuel line inside the tank, allowing the fuel to just spray inside the tank, and not build pressure in the system.
There is also the possibility of the pump working, but not pumping the correct pressure.
All of these can be checked with the fuel pressure tester.
I know most people don't have one just lying around. Some parts stores will loan you a tester if you buy parts from them. A tester can probably be rented from a rental place.
or you can buy one. Not all that expensive.
The pressure needs to (or should be) checked with the engine running, and not just deadhead tested by unhooking a line and connecting a gauge, since even with a restricted filter, the pressure would "buid" to what the pump can pump, but it may not have the necessary volume to properly operate.
With a gauge "T'd" into the system, the pressure regulator can be checked by pinching the return hose.
I don't know what type injection system you have on that car, so I will give a couple different pressures.
The pressure for a throttle body injection system should run at about 10 to 14 PSI...engine running. I like 13 PSI on that system. TBI looks like a carburetor under the air cleaner, but just has two injectors in the top of the throat. If you have that, you can see the fuel being injected if you watch with the engine running. Should be two nice cones of fuel spray.
On the other system that you might have, MPFI,(multi port/sequential fuel injection), there is a separate injector for each cylinder, and the pressure must be much higher. About 28 to 36 PSI.
On some later models, there are even higher pressures, but you should have one of these two.
You could just replace the filter, and that might take care of the problem. Good guess, and if it has never been changed, a good logical step.
Whatever you do, if the filter is a possibility, don't run the system without a filter in place, cause you could send a slug of trash right to the injectors.
Now...assuming you have good fuel pressure, and good volume, then the thing to check would be the throttle position sensor. if it doesn't send a proper signal, the ecm just guesses at how much fuel to inject.
But if the TPS is bad, the car will usually run good when cold, but switch to running bad after warmup. Same goes for oxygen sensors, vacuum sensors, and air flow sensors, since none of those inputs are used during cold engine operation.
So if it runs equally powerless first thing in the morning as after warmup, I would concentrate on the fuel.
I have a 95 Cutlass that had a jerky problem due to a broken valve spring on one of the intake valves, but when it wasn't jerking, it had lots of power, so doesn't sound like your problem.
Good luck,
Van
