1999 Escort ZX2 idling rough & not shifting in to overdrive

Question edited for clarity.
Question moved to model category.

Probably the IAC (idle air control) valve.

https://www.google.com/search?q=2000+ford+escort+zx2+idle+control+valve

More here

https://www.google.com/search?q=2000+ford+escort+zx2+idle+surges+at+idle

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No. Here is a link to a picture of your IAC valve:

http://www.rockauto.com/catalog/moreinfo.php?pk=941883&cc=1420489&jnid=510&jpid=0

Good Luck!

PS If your XZ2 is stalling, clean the carbon off the throttle body air intake area around and on the throttle plate.

Clean throttle body,put some fuel cleaner,could be IAC sensor.

Top off ATF and re-test.

When you put in N - netural can you get full range of rpm?

I have the same problem with my ZX2. First you have to find out what engine you have to find out what emission control system you have. if you have a ERG valve clean it and your throttle body. Throttle body cleaner is under 10 bucks at autozone. If you don't have an ERG valve you might need a new idle air control it is 100 bucks at autozone and on the ztec engine it is bolted underneath the throttle body. you should also clean your mass air flow sensor which is located in your air cleaner right behind your air filter, after all of that check all your vacuum lines for leaks and if that does not fix it you might need a new PCV valve this one is pretty cheap about 5 dollars.

should be located on the upper intake by the throttle body locate your throttle linkage and it will be in that area

If you can find the IAC valve(idle air control) on the throttle body-it should be replaced or try to clean..If you put in new plugs and they turn soot black in a short time period, you have other issues-possible internal engine,such as valve train problems, or a partial exhaust blockage, or the fuel your buying is not good...

Your IAC may be defective, first check the canister purge valve by removing the large hose off the charcoal canster and plugging the hose with a bolt or something you can fit into it, then try it also check PCV valve and see if it's bad. there are more things to check like fuel filter fuel pump and or fuel strainer if fuel tank but would need to have more information to help.

Check your IAC,, Idle Air Control solenoid. It is attached to the throttle body and controls the air flow at idle by bleeding air into the throttle body.