Need a bit of help from experienced 3geez mechanics re:an idle problem.

[KaMiKaZeE]

Well this is dealing with the LX-i hatch, and it has the surging idle thing going on where while sitting still the idle just goes up and down, up and down between almost stalling and about 1500-2000 RPM. I know that others have had this same thing, and I know that everyone says it is probably the fast-idle air valve, or a vaccum leak, or the PCV valve, or a fuel pressure regulator problem, or one of the many parts of the emmissions control system. Anyway, my question is, without replacing half my car unnecessarily, how do I pinpoint the exact cause so I will know what thing to mess with? I do work on my cars quite a bit so I'm not a total noob, but I get tired of replacing a bunch of stuff I didn't have to so if you guys can give me a simple testing procedure for the obvious stuff like the FIAV it would be greatly appreciated. Thanks!

[Justin86]

Well is the ECU throwing out ant codes. My was throwing a code 12 EGR and I took it off and cleaned it up, then my car ran fine. Before it would surge and then it would die.

[KaMiKaZeE]

Hey thanks justin I didn't even think to check for error codes. I've never tried to check any codes on a 3g though, and I don't have a code reader, so what do i need to get/do to check it?

[bigpoppa88]

Don't you read the codes on your ecu? It's under your seat, open the little door on it, you see it under the drivers seat from behind the seat....

[speedr409]

Codes aren't a lot of help sometimes anyway. I 'bout guarantee you its the fast idle valve though, have fixed 2 LXI's with the exact same problem, one my ex-GF's, by replacing it. Also make sure the car is completely full of coolant, thats an easy fix sometimes, but since the fast idle valve is higher than the rest of the cooling system, sometimes you'll get an air bubble in there. If you yank it (its on the back of the intake, pass side) and it doesnt look like it was full, then try filling it as much as you can and slapping it back on before much leaks out. Good luck!