colter

On my 89, I pulled the throttle body. And the passenger side valley on the back of the throttle body was packed with black soot. That comes from the line that runs to a solenoid I believe that goes to the charcoal vapor canister.

I've noticed that valley on the back of the passenger side of the throttle body plugged up before with black soot.

I believe the charcoal canister sends fuel vapors to the back of the throttle body and release them into the intake.

What would be causing the black soot to be plugging up the back of the throttle body valley? Does that mean the charcoal canister needs to be replaced? Or could it be fine pieces of the rubber lines that carry the fuel vapors to the throttle body is falling apart and those fine pieces are clogging up the back of the throttle body?

I know those black vapor canister hoses are pretty deteriorated looking and you get black crap on your hands from touching the lines.

Anyone know what size and type of hoses those are?

aklim

I would have thought it would be more of the PCV that causes black deposits. Still, it isn't a bad idea to take apart the TB (Cover, IAC, IAC housing) once in awhile to clean it. Reassemble with new gaskets

Cliff Harris

I think you're looking at residue from the EGR valve. The EGR passages are routed to just behind the throttle plates.

colter

It's not the EGR or PVC lines/routes. The black powder is packed inside the passenger side channel on the back side of the throttle body. The line going to that channel comes from the charcoal vapor canister.

Here's a random pic of the back of the L98 throttle body I found off the net. It's the right side channel that runs to the center of the back of the throttle body. It's packed with black powder that I've cleaned out a few times:



I'm thinking that's from the rubber soft hoses connecting things on the vapor canister lines. As when I touch those rubber lines, I get a thick black coating on my hands. So I assume if that is going on inside the rubber hoses, then maybe that stuff is attaching to fuel vapor and collecting in that channel in the back of the throttle body. And I'd assume it's also getting burned in the engine.

Or is it possible that could be charcoal or whatever it is inside the charcoal vapor canister?

colter

From searching around. Looks like what is probably going on is I'm betting the foam in the charcoal canister has failed letting charcoal to pass along with the fuel vapor into the throttle body. And thus clogging up the channel in the back of the throttle body and probably going into the engine.

So looks like a bad charcoal canister. Would be nice if you could easily take these apart and put in new foam filters.

steven mack

My lines are also Old and powdery.I get a small puddle of black water on my garage floor after a drive.I would replace the hoses first and see what happens.Thats what i'm going to try on mine first.

aklim

Just dump it. Mine fell off from rust. Wisconsin dumps salt, salt rusts, canister fell off. That's my story and I'm sticking to it.

colter

It makes sense that it is probably charcoal getting sucked into the throttle body from a failed foam filter in the charcoal canister. I had thought it might of been the charcoal as I didn't think it sounded right that it was coming from rubber hoses. Then I looked around and saw it mentioned a failed foam filter could allow the charcoal to get sucked into the throttle body.

I went ahead and left the hard line going to the throttle body disconnected so I don't have to take the throttle body apart again to clean it. Plugged the port though so no vacuum leak. I'll probably look at replacing the canister as they say letting the gas tank release fumes into the atmosphere will be wasting gas. Though don't know how much gas you'd be losing if it matters much cost wise.

aklim

FWIW, I plugged up the hose and let it be. But even if you vented to atmosphere, what do you lose? I'd say not too much.

colter

What hose did you "plug" up and how?

I took the canister out and unplugged the hoses. Turned it upside down and black pellets came out the port that the tank hose connects to. I'm thinking the charcoal has broken down over the years and so smaller pieces or dust like pieces can make their way past the foam filter into the throttle body.

I think what I'll do is get a used replacement canister and probably go ahead and get new rubber lines just because the old lines have sludge caked onto them on the outside and are dirty.

And I may get a small inline fuel filter to connect into one of the large rubber lines part that go to the throttle body. Maybe between the canister and the solenoid as you also protect the solenoid. As from that solenoid it plums to the throttle body.

aklim

Purge control solenoid to TB. Take that hose off on the TB and put a vacuum cap.

Remove hose on TB and hook up the EGR (if you still have it) into that vacuum source. Mine fell off so I just capped everything.

Insert screw into the hose to the fuel tank and use a worm clamp to hold it in place.

colter

Mine is routed like in that diagram. I've seen pics of others who have slightly different connections.

I disconnected the "purge" line at the throttle body and plugged the vac nipple. The vac line at the bottom of the throttle body connected to the EGR solenoid was left in place. Also that same line was left plugged into the "Tank valve" and also on the valve on the canister to keep from getting a vacuum leak and to let the tank vapor valve to still open to vent fumes. Assuming those valves don't leak.

Also connected the "Tank" hose to the port on the canister so it will release fumes in that canister vs. just an open hose laying around.

I had already halfway cut open the canister and dumped out the charcoal to look inside before I read of someone else using an inline fuel filter to keep charcoal out of their carburetor. I probably would have tried that first.

But I'll end up getting a used canister and just in case it may be going bad. I'll go ahead and put an inline fuel filter in the purge line inbetween the canister and solenoid. I assume the fuel filter would stop any charcoal, but allow fuel vapor to pass.