Q: Replaced the IAC on my 04 Xterra now idle surges

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Ok I got the 505 code a week ago I bought the iac and put it in replaced all hoses to the intake manifold clean the throttle body with carb cleaner off the manifold put a new tps on it's is adjusted to .50 in the specs said to adjust it to( .3 to .7) reclaimed every hose with new clams so there is no vac leeks everything is torked to specs mas was cleaned with electrical connection cleaner my problem is that now when I start it it idles @1500 rpms from cold start when at operational temperature idle surges between 15 up to 2000 RPMs as it reaches 2000 RPMs a bogs back down to 1500 in a continuous loop i rechecked all hoses and clamps no leeks and torque specs everything is on point the tps sensor is reading the correct adjustment on voltage meter mass air flow sensor is reading correct voltage on voltage meter can't figure out the problem if you can help it would be appreciated thank you

My car has 186000 miles.
My car has an automatic transmission.

Sounds like you have taken a lot of the right steps, but lets go back to the beginning. A P0505 code doesn’t necessarily mean the IAC is bad. Specifically it says that there is a malfunction in the idle control system. That could be anything from a bad IAC to a bad connector to a bad engine controller. You need to check carefully for bad connections at the IAC and throttle sensor and look for any ground wires that might be off. In most cases, the Idle air valve is normally open, and the ECU pulls it closed. So if it is not operating at all, you get what you have now. If your car is the type that has a hose going to the valve, you can pinch off the hose with blunt pliers and see if the idle drops down. If it doesn’t, you have an air leak somewhere else. If it does, that means the valve should have control so you need to keep working with the system that operates the valve. A proper scanner with activation features would be helpful at this point. To get help with this, contact YourMechanic. They can send a technician to your home or office to check out your high idle problem and let you know what is the solution.

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