I have a 96 Plymouth Neon with 74k miles on it. The engine seems to
randomly sputter when driving. It's hard to pinpoint when it does it, but
it seems to happen more often if I am on a hill, but not fully
accelerating the car. Say if you are going up a hill, but maintaining a
certain speed, such as you would on a freeway. The engine doesn't die, it
just sputters and if it doesn't kick back in, I just floor the accelerator
and the car runs like a champ. I was going up a massive hill in Souther Cal
that I was for sure my car would die on, yet it ran normal. However, I was
accelerating the whole time. When I was coasting up an off ramp of the
freeway the engine sputtered.

I just got it back from the service dept and I just had the throttle body
and fuel injectors cleaned yesterday. I turned it in to them, 2 times for
this problem. Both times the claim they could not get it to sputter. The
first time they gave my car back with nothing done to it, the second time
they cleaned up the throttle body and fuel injectors. Also, about 2 months
ago they replaced my fuel pump after it had gone out.

I'm still thinking that this is related to a shoddy install of the fuel
pump as it NEVER had this issue before the pump was replaced and a
co-worker suggested that I may have an O2 sensor issue. However, if the
car does die no codes are issued so it's making a very difficult thing to
track down. The spark plugs are about 2 years old, and the car is 99.5%
city driving, at most 10 miles a day. Could the plugs be getting fouled?
Could it be a bad tank of gas? I fill up about once a month, and I just
put a new tank in today. Maybe it'll work itself out?

Any ideas? It's almost coming to the point where I can deal with the
little sputtering, but I am afraid that one day it'll die on me at the
worst possible time.