Beware charcoal canister breakdown!

[AustinJohn]

I realize this is an old, old thread but having been chasing a "rough idle" in my '94 coupe (not the ZR-1) just ran across this and it was the silver bullet or at least one of three; the canister was bad, the line was clogged with charcoal pellets (blew those out with compressed air) and I replaced the purge solenoid while I was at it not knowing what was in it. All runs as it should now.

Many, many thanks! John PS The car gave me a BIG clue at the start of my hunt as opening the gas cap after a drive of any length (especially when it was a hot day) would release a tremendous "WHOOSH" sound but checking the Corvette Forum I found threads suggesting that was normal. In fact, it's not, just a symptom of a defective canister.

[gbrtng]

The canister on my 91 leaked enough fumes to cause the vehicle to flunk the Illinois emissions test in 2002 - the test used a pickup hose at each exhaust pipe and the RH hose detected the unburned HC content. Many dollars were spent trying to pass the test until the defective canister was discovered. What I'd like to know is which hose(s) do you inspect for carbon granules - I read the whole thread and nobody really answered that question ...

[AustinJohn]

I have not looked at the FSM for my ZR-1 but on my '94 the hose that can become plugged with carbon granules is the one that runs from the canister to the engine (the vacuum pulls the granules from a defective canister). The other hose, from the tank to the canister, is not subject to the problem as the vacuum is pulling the fumes from the tank to the canister. John

[Fully Vetted]

Hey, John. Good to see you hangin' around.

Thanks for digging this old thread up. After seeing it I was reminded that the PO of my car had mentioned something about replacing the canister back by the right rear wheel. I didn't have a clue what he was talking about so I just filed it somewhere in my brain. So, after going through all the parts I got with the car there it was. A brand new canister still in the box. I might as well put it on since I have it and it is 20 years old now.

Many thanks, my friend!

[PhillipsLT5]

I had trouble with mine, no longer, its gone, most of our cars experience the same problems

[Fully Vetted]

You "kludged" it? I didn't realize you could do that. What's the work around? It doesn't throw any codes?

[PhillipsLT5]

That's a ? for Marc, no emissions needed here

[AustinJohn]

Originally Posted by Fully Vetted

Hey, John. Good to see you hangin' around.

Thanks for digging this old thread up. After seeing it I was reminded that the PO of my car had mentioned something about replacing the canister back by the right rear wheel. I didn't have a clue what he was talking about so I just filed it somewhere in my brain. So, after going through all the parts I got with the car there it was. A brand new canister still in the box. I might as well put it on since I have it and it is 20 years old now.

Many thanks, my friend!

Hi David - Hadn't seen your dyno numbers before (430 RWHP/392 RWTQ). Very impressive. John

[We Gone]

Just a Question, I know this is after the fact but would be insurance to keep the charcoal bits out of the line could you add a small filter on the out going line? solid rock one like you use on an aquarium or paper fuel line filter?

[batchman]

Originally Posted by We Gone

Just a Question, I know this is after the fact but would be insurance to keep the charcoal bits out of the line could you add a small filter on the out going line? solid rock one like you use on an aquarium or paper fuel line filter?

Interestingly RockAuto lists a Vapor Canister Filter (Standard Auto #CF1) for use with 4 1/2" Filter, which sort of sounds like it belongs inside the canister... At $1.50 I'll buy it and see if there's a place to put it.

I've noticed a fuel smell at the rear before and I've been fighting an odd up-idle for a long time. Me thinks I'm in this club too, but it sounds like the purge valve is under the plenum?? I was really hoping it'd be easy to get at so as to blow out any crud.

Yikes,
- Jeff