98 Civic DX Surging Idle

[drewzo]

I have a 98 Civic DX that has a surging idle. The CEL code is P0505. I cleaned the throttle body and IACV several times and bought a used IACV at the junkyard; still didnt work. I bought a new IACV, the problem was fixed for a few days and now has gone back to surging. I have checked for vacuum leaks and bled the coolant system. I replaced the ECT because someone told me that could be a problem. The idle problem only starts when the car warms up. If I remove the TPS and MAP sensors, the problem stops. Obviously I get two new codes once I pull the sensors. If I clear the codes while the car is idling, it starts surging again.

I also have another problem that I'm not sure if its related or not.
While I'm driving, if I let off the gas while in gear, the car jerks. When I push the gas pedal again it jerks as well. It doesn't happen all the time and only happens when I let off the gas and initially push the pedal. I have replaced the engine and trans mounts.

I would appreciate any help, Thanks.

 

[Goodi]

I have the same "jerking" issue with my 97 hx, i can't seem to figure that one out either...

As far as the idling is concerned, i have done eveystep you have done, but for me it was just a simple vacuum leak. Try to doing a smoke test if you havent before. Check and double check your o2 sensors as well.

Good Luck

 

[drewzo]

I will check the 02 sensors. 2 of them are only a year old. I will also try the smoke test. I already tried looking for leaks with carb cleaner, but I'll try that too. I just don't know if its a leak though, because when I originally changed out the IACV the CEL went away. Then a few days later it came back. Thanks for the tip though. Let me know if you figure out the car jerking though.