Excessive vacuum leak
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Excessive vacuum leak
Engine light came on (horror) I took it to Advanced Auto for the free diagnostic.. machine said "Excessive vacuum leak" And there you have it. I figured it to be under the hood so I checked every hose on the thing and found nothing. So where else might I check? Or has anyone else experienced and cured this problem? 1997 F-150 V-6
Tuned
Joined: Feb 2009
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From: New Lisbon NJ USA
Check the hose that runs from the front underside of the intake manifold to the EVAP which is next to the master cylinder, on my truck(97 V6) that hose looked ok but when examined closely was very porous and was allowing vacuum leakage, also the rubber elbow that connects the PCV hose to the manifold needed replacing on my same truck as that had cracked and was leaking, After replacing both of these the truck ran and idled much smoother, I would go back over all the vacuum lines and recheck them just to rule them out as a source of the problem.
Val
Val
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p0455 specifies evap emissions, check the canister and all lines. hopefully you can find it since its large, if not you may have to have a shop fog it
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Posting Guru
Joined: Oct 2005
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From: Louisville, Kentucky
This is from the service manual on my 2002 F-150. It explains the EVAP system. Good luck! 
1 Check for the presence of a fuel filler cap. Tighten and check for correct installation.
2 Check the input port vacuum and EVAP return tube are connected to the EVAP canister purge valve.
3 Check that the canister vent solenoid is correctly attached to the EVAP canister.
4 Check for disconnected or cracked fuel vapor hoses or tubes between the intake manifold and following components:
- EVAP canister purge valve
- EVAP canister
- fuel vapor vent valve assembly
5 Check for damaged fuel tank or fuel filler pipe.
1 Check for the presence of a fuel filler cap. Tighten and check for correct installation.
2 Check the input port vacuum and EVAP return tube are connected to the EVAP canister purge valve.
3 Check that the canister vent solenoid is correctly attached to the EVAP canister.
4 Check for disconnected or cracked fuel vapor hoses or tubes between the intake manifold and following components:
- EVAP canister purge valve
- EVAP canister
- fuel vapor vent valve assembly
5 Check for damaged fuel tank or fuel filler pipe.
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Thanks KingRanchMan02 I will check all of that out. I did notice one thing different. On my 93 F-150 the gas cap clicks around even after I tighten it. On my 97 F-150 it only clicks once and is tight, and that's it, won't turn anymore doesn't click anymore. Does your gas cap only click once?
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Okay I put a new fuel cap on, will the light go out by itself? Also when I checked the big hose that went from the vapor management valve to the intake it turned my hands black. When you say EVAP... do you mean the vapor management valve?
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Okay I guess I'll go to the dealer tomorrow because NAPA, Advanced, and Parts + don't carry hose that big. I thought I could get away with gas line but it wouldn't stretch over the end of the tube. Same with that elbow, the gas line just wouldn't stretch over the tube. Believe me they all tried to sell me on the gas line. Well at least I have two feet of gas line for my next emergency (laughing)
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Hi, I know i'm posting to an older thread... but does anyone know if you can get a hose for the EVAP return... except the dealer. Not sure how much they charge, but I'm guessing its too much for a piece of hose. Mine is about in the same condition as the others posting to this thread. If you know a type/size of hose I could use instead, I'd really appreciate it. I see that autozone sells a set of 1/4, 3/16, and 3/8 red silicone vac hose... wonder if that would work.