IAC Valve question
Fleet Owner
Joined: Oct 2005
Posts: 20,785
Likes: 1,751
From: Kentucky
The picture is not 100% accurate....the Canister Purge (CANP) solenoid is not a sensor, it's actuated by the computer to vent the stored fuel vapors from the fuel tank charcoal canister into the intake tract. Early EFI engines did not have the solenoid. If you are not getting a code for a CANP issue, yours does not have one.
Note: the above implies the port for the CANP is before the throttle blades, therefore even if it was not plugged it would not be a vacuum leak. I would verify it is capped off just to prevent unfiltered air into the intake.
Note: the above implies the port for the CANP is before the throttle blades, therefore even if it was not plugged it would not be a vacuum leak. I would verify it is capped off just to prevent unfiltered air into the intake.
Fleet Owner
Joined: Oct 2005
Posts: 20,785
Likes: 1,751
From: Kentucky
Yes...on my old 1992 F350 this reservoir was completely rusted out on the bottom. Definitely a leak to atmosphere.
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 12
From: Sand Lake, MI
The picture is not 100% accurate....the Canister Purge (CANP) solenoid is not a sensor, it's actuated by the computer to vent the stored fuel vapors from the fuel tank charcoal canister into the intake tract. Early EFI engines did not have the solenoid. If you are not getting a code for a CANP issue, yours does not have one.
Note: the above implies the port for the CANP is before the throttle blades, therefore even if it was not plugged it would not be a vacuum leak. I would verify it is capped off just to prevent unfiltered air into the intake.
Note: the above implies the port for the CANP is before the throttle blades, therefore even if it was not plugged it would not be a vacuum leak. I would verify it is capped off just to prevent unfiltered air into the intake.
Yea good eye, that port is forward of the blades on it so wouldn't be a "vac leak", only allow for a very small amount of unfiltered air if left uncapped.
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 12
From: Sand Lake, MI
Its possible it has a CANP but its hanging/laying down below someplace, if a 90 model year had one or not I couldn't say, if it does it only need to be electrically active to prevent throwing a code.
Looked into it briefly and based on claims made the 5.8L got it in 89, the 5.0L not until 92.
That must be true "I read it on the internet"!!
must be another one of them "light duty" "heavy duty" things.
Looked into it briefly and based on claims made the 5.8L got it in 89, the 5.0L not until 92.
That must be true "I read it on the internet"!!
must be another one of them "light duty" "heavy duty" things.
Thread Starter
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Elder User
Joined: Oct 2013
Posts: 505
Likes: 0
From: Independence
This truck had two owners b4 me the plus side is the first owner kept it in the garage evey day. I know the body paint on these years was crap! It only had surface rust for the longest time! Even the wheel wells weren't even rusted through until a year ago! But yes i know it can still rust, just might take longer especially in the humidity and salt capitol of the U.S. lol but i will do some checking this weekend, hopefully! And get back to you!!
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Elder User
Joined: Oct 2013
Posts: 505
Likes: 0
From: Independence
One other thing gentlemen have you guys seen the thread on the internet about running the pcv valve where the brake booster is on the intake tree and running the brake booster, to the back of the intake is this a good idea you think? I know sometimes that elbow on the pcv valve could be wore out that's why i asked
Fleet Owner
Joined: Oct 2005
Posts: 20,785
Likes: 1,751
From: Kentucky
I did that mod on my old '92. The theory behind it is sound IMHO. While I was at it I installed a new PCV and eliminated the rubber section between the PCV and the valve cover and the grommet on the cover itself. That rubber section was dry rotted and a source of a vacuum leak. Another item that would be difficult to find with the "spray" test or propane. It takes some good detective work to track these pesky items down.
While working on the PCV mod I found the gasket between the upper and lower intake was leaking at several manifold runners. Once again no amount of spraying carb. cleaner found that either. Others swear by that method, I swear at it...
While working on the PCV mod I found the gasket between the upper and lower intake was leaking at several manifold runners. Once again no amount of spraying carb. cleaner found that either. Others swear by that method, I swear at it...
Thread Starter
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Elder User
Joined: Oct 2013
Posts: 505
Likes: 0
From: Independence
I did that mod on my old '92. The theory behind it is sound IMHO. While I was at it I installed a new PCV and eliminated the rubber section between the PCV and the valve cover and the grommet on the cover itself. That rubber section was dry rotted and a source of a vacuum leak. Another item that would be difficult to find with the "spray" test or propane. It takes some good detective work to track these pesky items down.
While working on the PCV mod I found the gasket between the upper and lower intake was leaking at several manifold runners. Once again no amount of spraying carb. cleaner found that either. Others swear by that method, I swear at it...
While working on the PCV mod I found the gasket between the upper and lower intake was leaking at several manifold runners. Once again no amount of spraying carb. cleaner found that either. Others swear by that method, I swear at it...
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Logistics Pro
Joined: Mar 2005
Posts: 4,698
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From: Mexico, Missouri
"Once again no amount of spraying carb. cleaner found that either. Others swear by that method, I swear at it..."
Totally agree with this. This worked to a point with Carbs, but I haven't seen it be of any use with EFI. I don't know why either.
I use a propane torch with a piece of clear poly tubing and use that to check for intake and vacumm leaks. Carburetor cleaner is the worst thing to use when rubber or a similar compound is used as a gasket between 2 surfaces. Either use MAF/Throttle body or Electrical Cleaner to check. These won't destroy gaskets.
Totally agree with this. This worked to a point with Carbs, but I haven't seen it be of any use with EFI. I don't know why either.
I use a propane torch with a piece of clear poly tubing and use that to check for intake and vacumm leaks. Carburetor cleaner is the worst thing to use when rubber or a similar compound is used as a gasket between 2 surfaces. Either use MAF/Throttle body or Electrical Cleaner to check. These won't destroy gaskets.
Thread Starter
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Elder User
Joined: Oct 2013
Posts: 505
Likes: 0
From: Independence
"Once again no amount of spraying carb. cleaner found that either. Others swear by that method, I swear at it..."
Totally agree with this. This worked to a point with Carbs, but I haven't seen it be of any use with EFI. I don't know why either.
I use a propane torch with a piece of clear poly tubing and use that to check for intake and vacumm leaks. Carburetor cleaner is the worst thing to use when rubber or a similar compound is used as a gasket between 2 surfaces. Either use MAF/Throttle body or Electrical Cleaner to check. These won't destroy gaskets.
Totally agree with this. This worked to a point with Carbs, but I haven't seen it be of any use with EFI. I don't know why either.
I use a propane torch with a piece of clear poly tubing and use that to check for intake and vacumm leaks. Carburetor cleaner is the worst thing to use when rubber or a similar compound is used as a gasket between 2 surfaces. Either use MAF/Throttle body or Electrical Cleaner to check. These won't destroy gaskets.
Thread Starter
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Elder User
Joined: Oct 2013
Posts: 505
Likes: 0
From: Independence
One of the only reasons im trying to get this problem solved is because, my daughter is getting ready to get her drivers license and she likes driving the ol' truck and i want it to run half way decent!! Im mean i just fixed the parking brake! It never worked til last week! Works good now though plus i got a utility trailer and i dont want all that weight on the trans. thanks again for the help!!!! Cant tell u that enough!!!!
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Elder User
Joined: Oct 2013
Posts: 505
Likes: 0
From: Independence
Ok, here's what is what I've done so far: looked at both VRES. I did see some rust but neither all all the way through. I pressurized them through manufold side didn't here any air through the, VRES. but it did blow back through the load side when reversed! Hope its supposed to do that! Im going to the TB, next! Thanks
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Elder User
Joined: Oct 2013
Posts: 505
Likes: 0
From: Independence
I also got rid of that TEE on the left side one to the intake manifold the other to the EGR vacuum solenoid like was suggested earlier since TAD and TAB solenoids are gone do to smog pump is gone.... Let me know what u think.... Thanks again Robert!!!
