Hi everyone, i have an 09 Galant ES (4 cyl Sport according to mechanic at an Auto Body Shop - ES part didn't fit correctly). There has been several times over the past 3 years owning this vehicle that when accelerating from being stopped at a red light or stop sign, the engine stalls. I have changed plugs and wires as needed for normal tuneups and this is still happens (once or twice in 1-3 month span). What could this be?

 

First of all, let's consider that you are accelerating. RPMs are high, and gasoline is sloshing back in your tank as well.

So my first guess is a lack of fuel. And that sounds like low fuel pressure. And that is most likely a fuel pump. BUT!!!

Before doing anything else, clean your throttle body, your PCV valve, your EGR valve, and your idle air control valve. Just eliminate them as problems. If your computer can't open the EGR valve, it can result in hesitation. The PCV has nothing to do with anything much, it just needs to be cleaned for the car to run well, as does the intake manifold. The idle control valve needs to open and close smoothly, and the passages need to be reasonably clean--one that sticks open can give you too much air, and the car then acts like it doesn't have enough fuel. So eliminate them as problems by cleaning them, which you should be doing every 30K miles or so anyway.

Put a fresh air filter in unless you are all caught up on the change interval for that (no body that I know is... <grin> ).

Pull your sparkplug boots and make sure they are free from oil. Misfires don't help.

One more thing to eliminate is to put some fuel injector cleaner into your fuel tank. Dirty injectors may let you get by most of the time, but on a acceleration run it may result in lack of fuel in the cylinders. Again, you should be doing this every once in a while anyway, and it eliminates a possible problem.

The next (cheapest) thing to change is a fuel filter, if there is one. Some cars don't have a separate one and rely on a screen/cloth filter inside the tank. Seriously. So you will have to find out what you have. Dealer parts department would tell you, by the way. If you want to look for it, many cars have them somewhere along the fuel supply line, often on the body about where a passenger door is. It is a can about the size of a beer can with the fuel line going in one side and out the other. Again, most people neglect changing it. I am not saying throw parts at your car, but I am suggesting that you should change your filters regularly anyway.

Having gone to all this trouble, is it likely that you fixed it? Not really. It still is probably a weak fuel pump.

The next thing can do is to measure your fuel pressure, which is the most likely problem anyway. If after changing the filter (if there is one), the fuel pressure isn't high and it drops suddenly when revving the engine, then either the fuel pressure regulator (usually at the fuel rail on most cars) is faulty or the fuel pump is weak. In order of likelihood, it is the fuel pump much more likely than and then the fuel pressure regulator. Why? Because your car is old. They just get weak. And die. I owned a 2000 Volvo 70 that I installed its 3rd fuel pump at 140K miles. So it can happen.

While you are around your fuel pump, check for the pump having a clean ground strap. I think my Volvo's second pump died due to a rusty ground. Or just old age, I dunno.

Fuel pumps are easy to change usually. On most cars there is an access point in the body of the car to the fuel pump. If not, you either cut a hole for yourself (only for those not faint of heart) or you drop the tank, carefully, removing three to five hoses and electrical connections, etc. as you lower it. I have done 3 or 4 fuel pumps in my life, and each was different, but none very hard. Just be really careful around gasoline. The fumes can explode really, really well. So no sparks, no open flames, etc. Wear gloves too--your genes will thank you.