Vacuum leaks
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5th Wheeling
Joined: Aug 2019
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Vacuum leaks
So I recently acquired a 93 f150 with 4.9 e4od. Truck has been a nightmare getting it to drive right. Finally got it road ready. Drove truck on highway for about 30 miles and half way through engine light would come on and off but not stay on. Light never comes on driving through the city. Got home and checked codes with engine off. Had no active codes but had code 172 in memory. Read it's saying o2 sensor lean. I was checking for vacuum leaks last night using a homemade smoke test. I had smoke coming from charcoal canister caps and egr valve. Is charcoal canister supposed to vent or does it need replaced?
Lead Driver
Joined: Oct 2016
Posts: 6,185
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From: Houston/Sugar Land
If the O2 sensor is bad it is sending a lean condition to the computer. In turn the computer adds more fuel to compensate. Since your code is in memory that could cause your rich smell. I suggest you get the truck to operating temperature and do a KOER running test. Different codes can be in the different test. Sandy
Lead Driver
Joined: Oct 2016
Posts: 6,185
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From: Houston/Sugar Land
Sounds like you probably need one even if it doesn't fix it. GL Sandy
Super Moderator
Joined: Apr 2004
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Is it missing, causing unburned fuel to give you that rich smell while in fact it's too lean to fire?
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5th Wheeling
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It actually runs good. Doesn't seem like it's missing. Only problem is, it is getting like 10mpg
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My charcoal canister blows smoke introduced with air pressure but holds a vacuum with a pump. These valves are supposed to release pressure so I think if you wouldn't see smoke they would be bad. At least that's what I came up with by myself. I might be wrong though.
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5th Wheeling
Joined: Aug 2019
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I think you may be right. I tried to spray carb cleaner where I believed it was leaking from but idle speed did not change. Also tried spraying the egr and no change as well.
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5th Wheeling
Joined: Aug 2019
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I didnt find one for $20. Was looking online at the time and first one that showed up was $20 but it was for a different vehicle. Ended up paying $40 at local parts store and only reason I got it for that cheap is because I have a business account with them
Fleet Mechanic
Joined: Feb 2007
Posts: 1,652
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From: Mooresville, NC
As for smoke leaking out of the canister, it has no moving parts, nothing to wear out so you probably just have cracks in the vapor purge connectors, lines...........you might also check the Canister Purge Regulator Valve.............I check this valve this way
Apply vacuum source to the side opposite the canister (5 in Hg) .........valve should not pass air if working, if it passes air it's bad
Apply 9V-14V DC to valve (I use a portable power supply) , valve should open once it gets the V, if not it's bad
Apply vacuum source to the side opposite the canister (5 in Hg) .........valve should not pass air if working, if it passes air it's bad
Apply 9V-14V DC to valve (I use a portable power supply) , valve should open once it gets the V, if not it's bad
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5th Wheeling
Joined: Aug 2019
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As for smoke leaking out of the canister, it has no moving parts, nothing to wear out so you probably just have cracks in the vapor purge connectors, lines...........you might also check the Canister Purge Regulator Valve.............I check this valve this way
Apply vacuum source to the side opposite the canister (5 in Hg) .........valve should not pass air if working, if it passes air it's bad
Apply 9V-14V DC to valve (I use a portable power supply) , valve should open once it gets the V, if not it's bad
Apply vacuum source to the side opposite the canister (5 in Hg) .........valve should not pass air if working, if it passes air it's bad
Apply 9V-14V DC to valve (I use a portable power supply) , valve should open once it gets the V, if not it's bad
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5th Wheeling
Joined: Aug 2019
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An another note I replaced o2 sensor. Drove it and still coming up with code 172 and also 411 which I have never had. Tried unplugging iac and it didn't change anything. Read somewhere it was supposed to kill the engine or almost kill it