i have a 99 ex 5 speed. starting the car and driving it cold to warm, or even when it just starts getting warm and drive, the car accelerates perfectly normal. after driving for 15-20 minutes the car mildly hesitates during acceleration between 1500 & id say about 3500rpm mostly in 2nd, 3rd & 4th. its not bad, but a light hesitation. any ideas what it could be? no CELs, the plug wires, plugs, dizzy cap and rotor are all new

 

Unplug the primary O2 sensor to see whether the problem goes away. If so, replace the sensor.

 

^ Ditto! same thing was going on with my 98 auto hatch. it was using a lot of gas and seemed to be hesitating when accelerating. Do that test and if it still does it then idk.

 

Which is the primary? The one on the cat or the exhaust mani?

 

Moved to technical chat.


The primary will be the first one on the exhaust (located on the manifold), before the cat.

 

My 00 EX coupe has the primary sensor in exhaust pipe A:

 

pulled the primary o2 sensor plug and the car accelerated in the same manner, i cannot seem to figure out why it hesitates

 

Did you install OEM plugs, wires, cap, and rotor?

Does the CEL work?

 

duralast gold cap n rotor, duralast plug wires, tried ngk platinum plugs and tried a set of ngk copper plugs, gapped them to .52 and tried plugs gapped to .44. The CEL does work because when i pulled the primary o2 sensor plug out the light came on. i reset it and still have no CEL

 

its not a violent hesitation or rough jerking, it will jus hesitate and lack power. usually when the car has sat for a while or overnight and is then driven it accelerates perfectly normal for the first 10 minutes or so. then once its warm, or if i come off of a highway into an urban setting and ill be rolling in 2nd or 3rd and if i go to accelerate it will hesitate and jerk all while still somewhat accelerating and once the rpms get to about 3500 - 4k its usually fine.