I own an 03 Honda Accord EX Sedan 4cyl Auto with 129000 miles. I have a hesitation while maintaining a constant speed between 20 and 50 mph. This hesitation doesn't occur at any speed below 20 mph or above 50 mph. The hesitation doesn't occur while accelerating or decelerating. The car idles just fine and has no other problems. I need help troubleshooting this one. Could this be a fuel pump going out or fuel related or am I way off base?

 

No Check Engine Light (CEL)? If yes, first step is go to Autozone, et al to pull the code w/ OBD2 scanner.

This has some charateristics of EGR lean stumble. However, this problem usually occurred when acceleration was started about 1500 rpm. Rather than accelerate, the car would "sag". Problem was caused by partial blockage of EGR ports in the intake manifold runs. Some ports were open and some blocked, and open ports got too much EG causing an overlean engine stumble. Accords have suffered w/ this for years, and I would have thought Honda had resolved this problem by 2003 models, but it's worth investigating.

You can check by temporarily disabling the EGR system. Easiest way is to pull the vacuum line to the EGR valve. Valve can't open at any time. This is likely to cause the Check Engine Light (CEL) to come on, but go ahead and drive to see if problem is resolved. If yes, you will needto clean the EGR passages and intake manifold ports. On earlier models you could reset ECU to eliminate CEL by pulling the BackUp fuse in the underhood fuse box for 20 secs. Later models may require an OBD2 code reader to reset.

Other possibilities are wires, spark plugs and perhaps a slow O2 sensor. If none have been changed, this might fix the problem.

It never hurts to clean the throttle plate and idle air control valve screen.

Fuel delivery is usually a on/off problem and not intermittent, performance issue. However nothing is absolute. Fuel pressure could be checked against specs.

good luck