Intake Question

[Koolhand]

On a 2002 Explorer 4.0 SOHC where it is written, "4.0L SOHC" on top of the engine, I am pretty sure that is the upper intake manifold. It looks like that piece is actually 2 plastic pieces joined together. If it is, is there a way to make sure they are joined securely? Reason I ask is because I believe I have a severe leak at this seam. I know it is common for these plastic intakes to leak, but this one seems to be a little worse than normal. Turn the truck off and there is a loud squeel coming from the upper intake and it appears to be coming from this seam. I have already been to 3 dealers, all say Ford says "vacuum leak type noise coming from the intake" is normal. You can hear this squeel from several feet away. Any insight would be appreciated.

 

[Billy177]

if you have a severe leak the ecu will throw a both banks lean code do you have a check engine light. i know on my 99 there was a recall for teh intake manifold gasket that was leaking

 

[Koolhand]

No codes. Everything sounds normal to me and 3 Ford techs until you shut the thing off. A second after you turn it off, a sound comes from the intake that sounds like air being forced out a small hole or crack. Only example I can come up with is letting the air out of a balloon while pulling the part you blow into tight.

 

[Billy177]

if you turn it off then press teh gas pedal to open the throttle body does the noise go away

 

[Koolhand]

I have'nt tried that. Good suggestion. If it does, could mean it's the intake leaking. If it does'nt could be something else. Do you know if that intake is actually 2 pieces? Thanks for the reply's.

 

[Billy177]

yes it is actually an upper and a lower i am thinking the throttle body adjustment screw may be off leaving the throttle body completly closed. have you tried cleaning your iac

 

[Koolhand]

I took it off and looked at it. Looked really clean. Engine idles good. May try spraying it down with an electric parts cleaner though. I've looked at the throttle body. Seems like when engine is off, butterfly is completely closed. I'll check it again in a minute.

 

[Billy177]

try adjusting the stop screw it should be open a little bit. the iac will compensate and the idle speed will be the same. i think the little holes in it are making the noise as air flows through them until the vaccum is gone

 

[Koolhand]

The way this one is set up, adjust the screw and it makes the butterfly hang open or close more. More open the butterfly, faster the engine idles, just as if you were putting your foot on the gas. I adjusted it a little, but it is not completely closed when engine is off. What RPM should this engine idle at I wonder? Thanks again for your help.

This is an edit:
Just did what you said. Turned engine off, squeel. Did this 3 times, squeeled everytime. Did it again but put put foot on the gas, no squeel. So now I think this noise is coming from the throttle body/butterfly. Problem is, the more I adjust the screw, the higher the engine idles. First time I did it it idled at 2500 rpm's. Got it backed down now to about 900. Actually think it should idle lower than that. I'm not sure if it is the IAC or not, but I may try cleaning it anyway.

 

[Billy177]

the iac should eventually correct the idle speed. try to get it running at 1000rpm it should then eventuallt correct itself to around 650 if it does not reset the computer and it should.

 

[Koolhand]

I'll adjust it again and disconnect the battery to reset the PCM. I've got it now to where it idles at 900 to 1000 RPM's, but that is where it stays. So what you are saying is I can adjust the throttle body adjustment screw, making the butterfly stay open more, just as if I had my foot on the gas and the IAC will compensate to correct idle? Probably a stupid question, but how does it do that?

 

[Billy177]

the iac is basically a throttle body bypass it is located directly under the cover that says sohc. i would highly reccomend cleaning it. there is a good chance that this is causing the wistling also

 

[Koolhand]

So I should be able to adjust the butterfly to stay open more and the IAC should compensate idle?

 

[Billy177]

i would clean the iac first and go from there, if it still wistles than try adjusting the throttle plate

 

[Koolhand]

Cleaned the IAC. It was really clean, but sprayed electrical parts cleaner in it and let it dry completely. Still squeels. Next I'll disconnect the battery, adjust the throttle screw 2 or 3 turns and go from there. Thanks again.

 

[Dr_Duke]

I've got a 93' X so I don't know if the IAC is the same on the SOHC, but I imagine its pretty close. A mech. I know told me that they cannot be cleaned. (well you can but it won't do much) Anyone heard of this?