Charcoal Canister

1992 4.0 AX15 NP242

I'm trying to figure out what problems rotted lines to the charcoal canister could cause. I've been hunting down a crappy idle and abnormally low MPG (10 to 12 city) for awhile now. I've narrowed it down to the wiring harness up until the other day. I was converting to a newer A/C system and noticed that the rubber hose going behind the block is pretty mushy. There's a metal tube that ends on the driver side firewall just before the valve cover and turns into a rubber hose. Would this have any effect on idle? I've tried to hunt down what exactly it does but aside from just dealing with fumes I couldn't figure anything out. Thanks

One of the vac lines to the canister goes directly to the intake manifold. If it of the canister has a leak, it will screw with the idle and fuel trim....

Ecomike said:

One of the vac lines to the canister goes directly to the intake manifold. If it of the canister has a leak, it will screw with the idle and fuel trim....

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Perfect thanks! Don't know if you remember my overheat issue I was having but found out the CSF radiator has a different neck than stock so I needed a new radiator cap. Gets here today but keeping my hopes high. If its not that than I'll be pulling the head to see if the jackets are clogged.