1996 Pontiac Sunfire hesitation/stalling problem

[steve jones]

We have a 96 Sunfire convertable with the 2.4 engine and a 5-speed transmission. The car has a bad hesitation problem when it's first started. It doesn't matter if it's hot or cold. Sometimes the engine will hesitate then stall, then it is very hard to restart. Once it clears up it runs great. I have replaced the fuel pump and filter, the spark plugs, ignition coils, the wires between the coils and the plugs and the air filter. We have been having this problem for six months now and it's very agrivating. Any suggestions will be appreciated, thank you.

[steve jones]

I removed the MAP sensor and noticed that the factory preformed vacuum hose was cracked near the sensor nipple. I replaced the hose. Most of the drivability problems have cleared up. Now under accelleration it sounds like the engine wants to blow the muffler off. I'm thinking of replacing the muffler with a high performance low restriction muffler.

[steve jones]

It's been a couple of days and the hard starting and some of the engine hesitation has resurfaced. Last night I replaced the fuel pressure regulator, cleaned the fuel rail and the exterior of the injectors. This seemed to help however; some engine hesitation remains. Two of the fuel injectors and the fuel rail were very dirty. I used a shotgun barrel cleaning brush to clean the fuel rail. I would like to know how to open the injectors so that I can flush them out. Does anybody know how to make a tool to flush out the injectors? Thank you.

[scooter10572]

it sounds to me like you have a clogged cat. conv. if I had seen your post before Id have told you to ck hose to map sensor,ive found alot of this on hi mile or older cars,but I would drop the exhast at the manifold and drive it,if is ok cat is bad.as far as flushing the injectors go and buy a tank of top tier fuel and run it, you cannot disassemble an injector and flushing them generally is done thru the fuel rail schrader port.Maybe you should take it to someone who knows how to fix it instead of throwing parts at it,I work at a dealer and have for 18 years and Ive heard your story hundreds of times,theyve tryed everything and now I have to fix it.

[steve jones]

I replaced the replacement fuel pump. It was only 4 1/2 months old. Now it starts and runs great. When I had the fuel tank out I emptied most of the gas out of it and found a couple of plastic pieces. I also put another fuel filter on it. I have thought about removing the converter. I removed the converter on my S10 and it made a wonderful difference in power and mileage.