2.5 V6 Sport Idle issue, Please Help!

[geeman]

Hi all! I have a 2001 Galant V6 Sport which I love dearly! I have had various OBD errors and fixed them but the last one is driving me nuts. Car drives fine but when rolling in neutral, revs plummet from 1500 to 1000 and bounce around the 1000 mark. If I put on the brakes it settles. OBD code P0505 is coming up. Have removed and cleaned the IAC and throttle body. Checked resistance across the two IAC coils, 80 ohms on both. Bought 'similar' Troform IAC for £25, split it, put the old plunger on the new coils (they all tested at 80 ohms too) and problem persisted. I have done everything I can think of. Even stripped and checked the wiring back as far as I could. Car runs great apart from that one little niggle! Any ideas???

[MarkSanne]

Maybe some vacuum leak somewhere? Are all the hoses secure and no (hidden) tears / rips in the vacuum and airlines? Vacuum/unmeasured air can cause a whole range of issues... A few other ideas: on the throttle body there's a manual adjustment screw. One shouldn't actually touch it, but... if it was done before? Another idea: could it have something to do with the Throttle body valve sensor? Maybe the sensor is not set up correctly.

[geeman]

Thanks for the reply Mark! I know the screw you mean, when I cleaned the throttle body it looked pretty well set so I left well alone! However, the TPS looks like it has been removed at some point, there are paint marks on the screws but they are centered... Pretty sure the hoses etc are in good condition but I will have another look. Cheers pal.