Idle Surge

I’ve got a 1997 Honda Accord wagon with the 2.2 VTEC and an auto trans. About 160,000 miles. A couple of months ago I went on drive of a little over an hour. I exited the highway and was on a surface street doing about 40 MPH when I got a check engine light. The only way I can describe the behavior was the car started bucking. Taking off from a stop I had to really give it the gas or it would sputter and jerk until reaching above 25 MPH. Cruising at a steady speed was OK. Surging idle from about 1000 to 1500 RPM in park . I nurse it home and pull the code and it’s a P0505 Idle Air Control Valve (IACV). I clear the code. The next day I start the car and there are no signs of a problem. Smooth operation daily for the next 4 or 5 weeks until I go on another 1 hour drive. I get to my destination and when I put the car in park I get a check engine light and idle is surging. After three hours I get back in the car. Still a check engine light but no bucking or jerking. No apparent driving problems but still surging in park. I get home and pull another P0505. I cleared the code and again I drove the car daily for a week without incident. I thought it would be a good idea to just install a new IACV.

I installed a new IACV purchased from eBay. It was claimed to be new but it may have just been a reman. I bled the coolant and the car will surge at idle in park or in neutral. No check engine light. Drop the transmission into drive and the idle stops surging and the car seems to run OK. Idles a little high but drives good. Maybe it’s a bad one so I ordered a brand new IACV from Autozone. Today I installed the new IACV, bled the coolant again the exact same symptoms. I could not stop the car from surging at idle in park or neutral. No check engine light. Runs fine while driving. I removed the new IACV and cleaned and reinstalled the original IACV. No surging and so far no check engine light. I can’t buy 2 defectives in a row. Why would a new IACV create a surging idle?