i cant figure out whats wrong with this damn van...

[Fire It Up]

My mom has a 2000 Honda Odyssey that threw a CEL recently. Checked it out with my friends OBD II, it was a P0505: idle air control. Indeed, the car would rev and cut the throttle a little bit when sitting at idle. Didnt have time to fix it myself since I was going to Canada in a day, so I took it to the dealership. They tested to see if a loose power steering cable was the source instead (apparently it can throw that code), which wasnt the problem, and after a bit they said it was indeed the idle air control motor. So my rents shelled out the $400 for the part (and some more for the labor), and since then, the problem has gotten obviously worse. The CEL has tripped again, same code. When you turn the van on, it idles normally with the CEL on. But as soon as you touch the throttle, the engine will start to rev from 700-1500-700-1500 RPMS over and over again. Eventually, the revs stop cutting and the engine idles at 1500, and as soon as this happpens, the TCS light comes on. And I checked, its not just a light, the TCS wont work after the revs stop cutting. Any ideas what the hell this could be? I'm guessing now its electronic...

[giant_mtb]

Take it back to the damn dealership.

[Secret Chimp]

Try disconnecting the IACV motor and see if it still acts goofy. It will idle low since the IACV isn't there to modulate the idle, but it would be interesting to see if the other behaviors or codes still pop up.