imDementeD

iTrader: (7)

Ok so i have a 92 sc300 that has had an idle issue for over a year now, sometimes itll run fine other times the idle is very rough sounding like a cammed out v8..
also at this same time the heater did not work..

talked to my boss about it he wanted to take a look, the valve it self seemed like it was still good but wasn't working..so removed the vacuum hose to find no vacuum??...not sure why tried to follow it back but couldnt really reach further down the engine(it was hot) so he just removed the vacuum line from the charcoal canister inserted heater valve vacuum line and it worked great...heater works perfectly ..but also my idle issue is gone?..car starts right up and idles perfectly


so..my question is..why is having the charcoal canister hooked up to the manifold causing this issue?..is the canister bad? ..any help is appreciated! Thanks!!

Ali SC3

iTrader: (10)

that vacuum hose does not always have vacuum. During cruise or whenever the vsv goes off, it puts vacuum on the canister to relieve the pressure in the tank. your canister was probably not being released for some reason, likely a faulty valve on the canister or faulty vsv (next to the intake manifold if you follow the hoses to it).

Now you have vacuum all the time on your gas tank which is not ideal, you may want to fix the original problem.
When the canister builds up pressure, the gas tank builds up pressure which is not good at all.
The fuel system gets affected and if you had a wideband you would see a very lean condition from the pressure in the tank, and it makes the car idle horribly with popping and general roughness.

you may also notice a really bad smell every once in a while, especially if you have the a/c on.
when the canister builds up too much pressure, there is a safety valve that comes out the side and it dumps all the pressure (and vapor) into your engine bay more or less.

So if thats the case you likely have a bad canister, or vsv, or maybe a leak so double check the vacuum hoses for cracks.

imDementeD

iTrader: (7)

thanks for a response, I didnt mean that the canister is suppose to have vacuum all the time, what i was saying is the vacuum to the heater valve did not have any vacuum. So i removed the canister vacuum and left it unplugged and plugged in the heater valve so now i have heat . However i was trying to figure out why the canister would cause that horrible idle. So you are suggesting a possibly faulty valve on the canister..which would probably explain the issue something with the canister is definitely causing the problem. When its disconnected the car starts and runs beautifully, however when its connected it runs horribly. So maybe just grabbing another canister would fix it? or can i just replace the valve? Thanks for taking time to help figure this out.

Ali SC3

iTrader: (10)

mine would do something similar is the only reason I know that it can affect your A/FR's so much.
thanks for clarifying the vacuum issue. I get the problem now.
Since it idles fine when there is no vacuum on the canister, I would think the canister is bad because it should actually become worse if there is no vacuum on the canister as pressure builds up.
So if pressure isnt building up you may have a busted canister or the check valve is broken but its hard to say without playing around with it.
alternatively you could have a canister thats gotten filled with fuel, and when it has vacuum on it it sucks the fuel into the intake and it runs bad as well. even with the vacuum line off and pressure building up, it may appear to be running alot better than when it was dumping fuel.

best part is all 3 can be addressed by removing the canister and venting the fuel tank, or replacing the canister and the vsv's, the charcoal system doesn't have many parts.

imDementeD

iTrader: (7)

yea since i have tomorrow off i believe im going to tinker with it a bit and see what i can discover and clean my motor up a bit so i can take it to a local shop and have them do a comp check/leak down test/pressurize the coolant system and check a oil leak(i believe valve cover gasket and/or dist gasket)