advice/help on excessive idle speed on 88 ford 2.9l v-6

[mpierce]

I am in Phoenix, Arizona. I recently acquired an 88 Ford 4x4 Ranger 2.9l v-6 engine 5 spd manual tranny. Saturday it was very damp/cold (for Arizona that is!!!!) It was then that the engine idle speed accelerated from its set 1100 rpm's to 2,000+ rpms, and would not kick down. I checked for stuck/frayed throttle cable etc, vacuum connections, all good. My Haynes manual research points out to a possible malfunction, something wrong with the Idle Air control (IAC) bypass air idle speed control (BPA-ISC) solenoid. Does anyone have any experience with this??? I know that this solenoid is responsible for idle speed, and wondering absent the other factors that I trouble shooted, that this could be the problem???:headbang

 

[allnpt0]

Check your throttle position sensor. Thats what I normally see as the culprit.

Pete

 

[mpierce]

thanks for that suggestion. It makes a lot of sense, in addition to the IAC. it's somewhere in that system!!!

 

[racsan]

i dont know alot about the 2.9 but once i had a high idle with my '93 4.0 and it ended up being a failed gasket on the fuel rail, dont know if the 2.9 uses the same design, but its a possibility. i too couldnt find any vaccum leaks and replaced almost every sensor on the motor before pulling the intake down and finding the gasket on the fuel rail has pulled in at the front and rear of the manifold.

 

[mpierce]

thanks for the help!!!!! before I begin replacing all the sensors, I'lll check out the gasket on the fuel rail, that could be the thing!!!! It's not that the idle is eratic and going all over the place it just sticks now at 2000 rpm's and won't kick down to it's normal 1100 rpm's. thanks for the help. best regards, Michael

 

[racing83x]

the IAC went out on a 3.8 t-bird sc i know of( crazy ex's) and it did the same thing you are talking about just go buy a new on and its on the throttle body i do believe

 

[Duane867]

Actually the IAC is the most common culprit on a 2.9L for high idle condition.
That and the accelerator cable.
I would start 1st by cleaning the IAC.

 

[4.0B2]

yes.. iac usually. dang thing never seems to do right lol.. i even tried to shorten the shaft on one- and lengthen it on a different one.. neither helped lol