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helloall.. i got this truck hasnt run in 15 years. got her running. she was idling at 1800 . its missing air filter housing.and tubes. I blocked off the big tube coming out from where the iac goes. idle went down to 1500. the pcv is working good. i blocked off any open ports. the vacuum hose coming off the brake booster is cut off. Does anyone know where the port it connects to?? i unplugged the IAC but it didnt do anything.. Does that IAC vacuum hose have to be connected to intake hose or can i just block it off???

that big vacuum hose coming off the IAC. i know it goes into the intake pipe that i dont have. is there a check valve where it connects??? WHY WOULD vacuum just be sucked up into a the intake vacuum///????
 

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Idle air bypass hose is connected to the filtered portion of the air intake inlet. It bypasses air around the throttle blades to modulate idle speed.
There is a vacuum T in the rear on the intake depending on year. Search for a large vacuum leak.


SJ
used 2b RHP


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Discussion Starter #3
thanks. so that bypass hose has to be hooked up or it wont idle??? the truck is a 91 f350
 

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well i went outside. in back of the plenum there are 2 ports .one line goes to pcv other goes to map. then there is a vacuum tree to the right of thermostat housing. those are plugged up. I still dont know where the brake booster port is. ???? that's hose is missing on the truck.. maybe it goes to the top port on vacuum tree??? although i wouldn't think it would be shared and ran to front of engine.
 

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Not wanting to highjack this thread but what are these trucks supposed to idle at?My 94 idles around 1200 and 1500 when I pull off highway until I kick it down.Lowest I’ve seen is 1150.
 

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Not wanting to highjack this thread but what are these trucks supposed to idle at?My 94 idles around 1200 and 1500 when I pull off highway until I kick it down.Lowest I’ve seen is 1150.

Any check engine light or codes?



SJ
used 2b RHP


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Any check engine light or codes?



SJ
used 2b RHP


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Lights flickers on occasionly(on for hr off for hr).I am hopeing I can clear up that when my headers show up Wednesday.I have been constantly chaseing exhaust manifold leaks since I bought that truck.Maybe this solve that.
I haven’t looked at codes for a while.
How do I reset them?I am not sure which codes apply due to I’ve never cleared them.Truck runs smooth otherwise.
 

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If you do not have a scanner that allows you to clear codes you can clear codes by battery disconnect for a few minutes.

Check codes as they present.


SJ
used 2b RHP


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Discussion Starter #11
Great news. Where was the problem?


SJ
brake booster hose was broken and not connected.. finally found where it connects.man cant get back there unless you take plenum off. I have another question. I think my iac isnt working. I disconnected it and nothing happened. Also the bypass hose is sucking huge vacuum i had to plug it. I dont think there supposed to be vacuum unless maybe full throttle on highway??? Does the IAC control the air bypass????
 

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Discussion Starter #12
here was my problem. the two connection were off the tree. i cant see if there's a third. tight as a clam's vagina back there.



91062
 

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Lights flickers on occasionly(on for hr off for hr).I am hopeing I can clear up that when my headers show up Wednesday.I have been constantly chaseing exhaust manifold leaks since I bought that truck.Maybe this solve that.
I haven’t looked at codes for a while.
How do I reset them?I am not sure which codes apply due to I’ve never cleared them.Truck runs smooth otherwise.

you can plug up all your vacuum ports .then make sure your pvc and map is getting vacuum and not leaking. clear the code.see if it stays off. truck im working on has been sitting for about 20 years no floor left. i plugged up all lines except for map and pvc and i have codes. well light is off.
 
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