I have a stock 99 EX and recently it's developed the p0505 issue. I've seen this on many threads but none of them seem to come to a conclusion, so I'm looking for help!

At around approx 1500 rpm engine pulses erratically with throttle pressure, and releasing and reapplying pressure to the throttle while driving produces a violent jerk. The car will buck if you are in that 1500-1700 rpm range. This only happens when the car is at operating temperature. The car idles at 1400 when this is going on and doesn't drop unless you turn off car and restart or clear the code.

1. Sitting at a light, the idle will suddenly rise about 400
2. Cel will immediatly come on
3. What I described above will happen

If I clear the cel while driving the issue suddenly goes away but will come back a day or 2 later. So far I've checked for vacuum leaks and cleaned the iacv, but that only worked for a few days. Please help!!! I have a scanner that shows some live data if that helps!

Ps: car also has p0420 which is a cat code and is probably unrelated FYI

 

Clean the IACV.

 

As mentioned, I have already done this. Looking for other ideas/tests

 

Check idle screw?

 

Try bleeding the cooling system. As suggested by tony, there's a diagram in the FAQs sticky for adjusting the idle speed.

 

Check if the IACV is operating like it should

 

Do you have any precat exhaust leaks or broken exhaust manifold studs? Are there any exhaust cracks near your o2 sensor bung?

 

Hey did u ever figure out the solution back then? I have the exact same problem.

 

yes!! It was the air assist solenoid! Do no bother messing with the iacv! Looks like this.

 

Thank you for updating the thread with the solution so that others who come looking in the future can be informed.