I have a 1989 honda civic lx that has been a great car.Lately it wants to shut down after running for awhile. It starts fine in the morning or after sitting around.And when its running down the road its fine.It usually takes about 15 to 20 minutes for it to fail.It will not start up right away but it will after about 5 minutes. I have already changed the fuel pump and fuel filter but to no avail.I finally checked the led error code right after it shut down and it flashed a code 15 which is the (ignition output signal).I guess I am just asking if anyone knows what I should try at this time.What part could be causing these symptoms?I appreciate your time and sorry about the long explanation.