New to this brand of car, 2000 s40, I really like it. Running like crap, changed the plugs and coils/wires. runs great now except the idle surges terribly , 1000 rpm to 2500 , where should I start? Thanks Todd

 

I'd check vacuum lines. There isn't much that will cause that sort of behavior, and vacuum lines are at the top of the list.

There are a number of vacuum lines that run from the throttle body area. If it looks like there's a line connected to each of them I'd remove them one by one and plug them with my finger and see if the surging goes away. (Warning: Be careful when removing as you can cause the aged vacuum lines to start leaking... even if they aren't already...) The line that when capped at the throttle body causes the surging to stop is the one that is leaking. Replace as necessary.

 

Idle Air Control motor dirty or defective. MAF needs cleaning. Just guesses.

 

Of its turbo's check the hose from the intercooler to the intake. That's known to break

 

Thanks for the tips I will let you know what I find.

 

I checked for any vacuum leaks with carb spray, nothing found. I removed the idle air control valve , soaked it with carb cleaner then lubed it up, cleaned the connections on the 2 wire plug put it back on and it runs perfect, no more surging. I don't know whether it was mechanical ,cleaning it or electrical since the plug was really corroded but it runs as it should now. 5 minute fix. Thanks.

 

I thought I had this fixed but it started surging again. I removed the idle air controller again and soaked it for a few hours and it ran fine again for a hour or so and started acting up again. So at least I narrowed it down to that part. Next I got some gasket material and made a new gasket with just the bolt holes essentially blocking it off. Reinstalled the iac left it plugged in,turned up the idle manually and it runs great. No issues hot or cold start idles about 7~800 nice and smooth. Thanks.

 

I went thru about 3 IAC units when i had mine. Finally occurred to me on the third one what the problem was...it said "Ford" on the part.