Just bought a 1999 Ford escort with 2.0 sohc 102000 miles 5 speed. Came to me mechanically sound except for a high idle throwing a code for IAC duty cycle to high. It's idling around 1250 and when I push in c clutch coming to stop it revs to well over 2000 before settling again at 1250. New IAC valve no change. I've emptied 2 cans of starting fluid on every vacuum line I can find and no change in idle. Pcv valve in working order good vacuum. Where else can I look?
I would not use starter fluid to check for vacuum leaks. It is extremely combustible and could easily cause a fire. Use carb cleaner or WD40 or something less volatile.
I would replace the PCV valve.
Only other thing off hand is the pcv. I would do what YASER said and replace that. If that doesn't fix it, double check all vacuum lines are tightly secured. Get a scanner and look at live data. If it's running lean and you give gas and it goes to normal then you most likely have a vacuum leak. That can help norrow it down a little. I would still start with the pcv as said Earlier.
Copy that I will check pcv this evening or just replace it they're cheap as hell. I was going to ask what the fuel trim should read because I have no idea what normal would be. I'll get back to guys this evening thank u!
As close to 0 as possible. Check it when car is fully warm. Overall you want it under 10% combine. How to calculate fuel trim. Example stft +1.5 , ltft +2.5 mean your fuel trim is +4.0% . Another example stft +2.0, lftf - 3.0
fuel time is -1.0 .Your car is older so it isn't to big of a deal if there off a little, that is common with age.
Did you replace the gasket for the iac . Also check the wiring make sure you don't have short.
I did put new gasket on. Also cleaned throttle body and discovered very dry and cracked vacuum line going to bottom of throttle body and replaced it. Got the idle to drop 100 so now on at the 1100 range.
Maybe check the throttle cable pr throttle body.
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I did check the cable all is well there I even disconnected it from throttle body and started it to set if that would make a difference and sad to say no it didn't....
So I just went ahead and relaxed pcv valve and that was the issue! Thanks guys!