Issue with Throttle sticking while driving

[mugsy86]

Hi everyone
I am new to the forum so any assistance would be greatly appreciated. I have a 1986 Mustang GT and I have been having an issue with my throttle sticking 15 minutes or so while driving. Tends to stick at 2K to 3K RPM. If I pull over and shut the call off and start again it will correct itself. Can anyone tell me what could be the issue? I could start off with replacing the throttle cable but to me it doesn't seem mechanical since I can correct it by shutting it off and starting it again. I could be wrong any help would be awesome.
Thanks

 

[broncojunkie]

Welcome!

There are a few issues that could cause that. I would start off by pulling your iac off and checking/cleaning it, along with the opening in the intake where it connects. When you remove it, you'll see what I'm talking about. They get carbon built up inside and it can cause problems.

Check for vacuum leaks, too. Spray some carb cleaner (or something similar) around the engine and see if the idle changes. That'll help you pinpoint leaks.

If those don't fix your problem, then do a search for "hanging idle". I believe there can be issues with the vss that could cause it, but I'm pretty rusty on efi cars. All of my foxes are older carbed models these days. I got pretty acquainted with these efi systems over the years, but it's been a while lol!

 

[mugsy86]

Thanks I'll give it a shot and let you know.

 

[mugsy86]

Hi just giving an update. Checked the iac and it was clean. I cleaned it anyway just in case. Next is to check for vacuum leaks. I did drive it last night and still have the issue. Was coming home from a buddies house and sure enough throttle was stuck again just driving around the corner after pushing it pretty hard. I pulled over shut the car off, started it and back to normal. Very odd.

 

[540Hotrod]

First..clean throttle bore and make sure the screws on the blade are tight and plate doesn't stick mechanically. I usually find it best to go through the full procedure. Unplug IAC and make sure it's idling at a low speed. Set the screw to hold maybe 500-600 RPM. The IAC should kick it up. If it idles at normal speeds without the IAC it can't control things. Then double ck the TPS voltage. I recently had one where the voltage would stick high when it was closed. Once I fixed that and set the base idle..the 200K mile IAC has worked perfectly. But as mentioned, ck vacuum leaks. Those two big hoses hidden under the upper plenum are often leakers.