High idle issue and leaking after running.

[PHoffman]

Hello everyone! New to forums or threads. I have a 1987 Ford Mustang 5.0. I bought it a couple years ago and have only fixed the convertible top. The car starts up every time and runs smooth. As of lately, the stang starts up high idle RPMs over 1000 and after 15 to 20 seconds it drops to about 700 and jumps to 900 and keeps jumping aka struggling. Sometimes it will even out and find the correct idle but seems to struggle. My brother and I started doing research and started working on it (No car expert by any means). First thing we did was test the TPS voltage and it was at .6 to .7. Which I believe is low. Next thing we did was replace the throttle position sensor and was still idling high and RPMs were jumping up and down. After that, we got some carb cleaner and took off and cleaned the idle air control valve. It was pretty dirty so thought it would solve the issue. Put it back on and still the same issues. I went and got a brand new idle air control valve (with no harness) and replaced it but still idling high and RPMs jumping. After letting it run and driving it so the computer reads the new part. The car was struggling more and wanted to die when started it up. Pulled it in the garage and it was leaking something possible coolant (That’s what it looked and smelled like). I couldn’t tell where it was coming from but saw a lot on the bottom rail of the alternator. I went under and looked and it looks gunky but the oil filter but couldn’t tell where the leak was coming. I am no expert and I am learning. I could use some help on the next steps or where to go from hear. After research, I am reading it could be vacuum hoses or EGR. The original issue is the high idle but after the car was running seemed like it was running hot and little white smoke out the exhaust with some leaking. I can post pictures but everything would look clean besides under it. Willing to try and fix some stuff myself and can use help. This is my first forum and post. Thank you!

 

[General karthief]

Welcome to
There is a lot of info in the tech/how to thread here, I'll link a thread that has the info you need to help locate and fix surging/high idle:

Help me create the "Surging Idle Checklist"

Updated 05 July 2022 to add rough idle when cold and smooth idle when up to normal operating temperature. See the EGR tech information, section #15 for more help. Many of you are familiar with the "Cranks OK, but No Start Checklist for Fuel Injected Mustangs" checklist and the No Crank...

www.stangnet.com

Follow the directions and if you have any issues spacific questions ask in this thread, that said, most idle issues are vacuum leaks so go over the vacuum lines, most common oil leaks are valve covers and the intake at the front or rear wall.
Hey, lets see some pics of what you're working on