Intermittent high idle

[90MJ]

1990 2.5 is idling around 1200rpm on average. Sometimes as high as 1500, rarely idles at normal rpm. Has done it since I got it a few months ago. I was thinking IAC, any suggestions?

[90MJ]

Actually looking at this engine now, I don't see an IAC. Just fuel lines and what looks like a throttle position sensor? I don't know the 2.5 like I know the later 4.0's so any suggestion is appreciated. Its not extremely erratic but I would really prefer to get it idling at the correct rpms.

[Ωhm]

2.5L uses a stepper motor with Closed Throttle Switch (CTW) located in the tip of the actuator.

[grumpiebill]

1990 2.5 is idling around 1200rpm on average. Sometimes as high as 1500, rarely idles at normal rpm. Has done it since I got it a few months ago. I was thinking IAC, any suggestions?

What Ohm said...

Sent from my LG-M210 using Tapatalk

[90MJ]

So basically I need a new stepper motor it sounds like. Its fine as far as driving. Only an issue at idle. Do you think it will hurt anything if I push off replacing it for a while? What is the actual name of the part? When I looked up what you called it I had no results

[Ωhm]

17 minutes ago, 90MJ said:

What is the actual name of the part?

Idle Speed Activator Control Motor. This is just one of its many names.

 

Many things can cause high idle. Check for vacuum leaks, hung up throttle cable. Check basic things first.
 

[90MJ]

Only thing i didn't do is spray the intake and vac lines, I'm out of brake cleaner. I DID however find an oil soaked vac line a few min ago that was really loose between the rearward top port on the valve cover going to the lower nipple on the intake side of the throttle body base. Replaced that and in reduced the idle to about 900-1000 now. I think i am just going to replace all of the vac lines. The PO let the valve cover leak way too long and everything is soaked under the hood. I replaced the valve cover gasket but can't seem to find the correct grommets for the top of it so it still steams oil mist out. I aspire to make this engine leak free. The firewall and everything looks mint when its cleanes off. Guess all that oil under the hood prevented rust over the years haha

[cruiser54]

These are failure prone.

 

And so are loose intake manifold bolts. 

 

 

[90MJ]

I will check it out. Thanks! The lower one in the pic is the one i found leaking. 

[90MJ]

If I pinch the vacuum line going from the valve cover to the lower port on the TBI it idles perfect. Can I just cap that off and install a breather on the valve cover?

Update: I capped it and just drove to work. Idle is steady at about 850. Runs smoother than it ever has since I bought it. Screw it, if it works it works