Intake manifold sucking air????

[gmoutdoorsman]

Keep getting a P0507 code for Idle air control system higher RPM than expected. Replaced the IAC with a good looking used unit. Idles around 1200 RPM, along with hesitation while cold.I can hear what sounds like an air leak near the rear of the upper intake manifold,could this be the root of my problem?

 

[tscherbi]

Yup spray back there with some carb cleaner or brake cleaner and if it fluctuates in rpm there is your problem

 

[Horns]

Most likely a vacuum leak.

 

[gmoutdoorsman]

checked all the vacuum points and its all good.i used starting fluid and when i spray around the CPI plug in the center of the upper intake manifold it choked the motor down to normal RPM.so im just guna replace the upper intake gasket as well as the CPI and TB gasket. I think that'll fix it

 

[SAATR]

checked all the vacuum points and its all good.i used starting fluid and when i spray around the CPI plug in the center of the upper intake manifold it choked the motor down to normal RPM.so im just guna replace the upper intake gasket as well as the CPI and TB gasket. I think that'll fix it

Sounds like that may be the culprit. Check the upper manifold for cracking while you have it off.

 

[gmoutdoorsman]

Ive had it off already and didnt seem to find any defects.I did notice the O ring seal for the CPI was stretched and hard to seat in the upper intake manifold

 

[SAATR]

Ive had it off already and didnt seem to find any defects.I did notice the O ring seal for the CPI was stretched and hard to seat in the upper intake manifold

They can be a pain to seat even when new and clean. Vaseline works well to grease everything up. Unless I had just installed it, I would not reuse the O-ring; they take a set and flatten out with heat cycling and pressure.

 

[gmoutdoorsman]

Ya thats my problem im sure. Just guna pick up an upper intake Gasket set ($25) comes with the upper intake,CPI,and T.B. gaskets.and Thanks for the tip,will use grease or something to help seat the Gasket in the upper intake