charcoal canister and EGR carbon build up fix?

[ARCHINSTL]

dlb - the pintle shaft can, of course, wear on our youthful cars, even though it does not move that much or that often, compared to head valves - maybe wear is more likely due to less-than-perfect material used.

Anyway - my EGR valve was, literally, a solid chunk of carbon inside at 170K miles when I got Goldie. Following the procedures in my link, I was totally successful in clearing it (note my ho-made vacuum tester in the photo). When I did it a second time (after flunking the emissions test yet again), I used the referenced oven cleaner and had by then gotten a vac gauge/pump and it held a vac totally, which did surprise me.
The oven cleaner was part of my desperation ploy - but I think I passed because of other stuff I did.
Tom M.

[dlb]

right, but i'm not questioning that, tom. i'm seeking a clarification of terms.

my question is when we talk about worn pintle shafts, are we talking about the SHAFT itself or the END of the shaft? when i hear shaft, i think of the long slender area that doesn't seal anything--like a valve stem, as 4WDC said, as opposed to the end of the shaft which is the part that acts as a valve. i want to clarify because i don't see how the 'stem' could be worn since it doesn't contact anything.

the EGR i played with yesterday wasn't really too badly carbon'd up. i was able to scrape it out quite easily. haven't messed with the charcoal canister yet, though i spoke with an old mechanic friend who said that i might be able to cut to canister open, dump the old charcoal out, fill it with charcoal from water filters, and then JB weld the canister back together. i thought that was a neat idea but i'll try cleaning it first.

[4wdchico]

hells bells, i was hoping you were going to chime in on this. i think you must lurk here far more than you post, 4WDC.

that is great info. what i now want to clarify with you is where the vacuum leak is occurring, exactly: you said that the pintle shaft is similar to the stem of a valve, but it doesn't seem like the shaft of the EGR valve would see much wear. i think that between the face of the valve and the body of the EGR is where a leak would occur, due to both physical wear of the two surfaces and carbon buildup on them as well. am i on the right track there?

next question: knowing your savvy nature when it comes to emissions stuff, what have you done in the instance of a leaky EGR? have you bought a new one for $185? if it was leaking due to carbon buildup it could be cleaned up some by applying vacuum to the diaphragm to hold the valve open while you scrape it, albeit blindly. if it's worn out though, you'd be SOL and have to either bypass or replace it--presumably with a brand new one.

First, yes, the most common failure mode for an EGR valve is a vac leak of atmospheric air into the intake via a worn pintle shaft/EGR body interface. Yes, this is by far and away why most EGR valves are replaced. I think that you are possibly confusing the different types of leaks that can happen involving an EGR valve.

First, and most common, is a vac leak of atmospheric air into the intake via a worn pintle shaft/EGR body interface. Yes, it is inevitable with enough miles driven. Remember this is a sliding interface that is not lubed by engine oil like the trace amount of oil that gets past the valve stem seals and lubes the valve stems in the valve guides.

Second would be the EGR diaphragm leaking. This would create a vac leak thru the vac system, unlike a direct leakage of ambient air right into the intake manifold like the pintle/body leak. This is a bit of a remote possibility & the one that almost all shade tree mechanics tend to obsess on. However, this leak must be ruled out before applying raw, unmixed propane to the openings in the underside of the EGR diaphragm canister to check for a pintle leak, or a misdiagnosis may happen.

Third would be the actual EGR valve leaking exhaust gas into the intake manifold when no vac is applied to the diaphragm. Yes, this does happen once in a while, sometimes they respond to cleaning.

The fourth kind of EGR valve leak would simply be leakage where the valve is attached to the supply of exhaust gas or on the intake manifold connection.

Actually a very common problem with EGR systems is no EG supplied to the valve due to a carbon blockage in the EG supply.

i have replaced many EGR valves for the pintle leak issue & none for any other reason on my own vehicles. I actually got really lucky last time I needed an EGR valve and found an almost new one for my t4wd on a scrapped car in a JY.

[dlb]

an update: i managed to save one of my charcoal canisters by trying petros' suggestion of soaking it in dish soap and water. i blew it out with compressed air and it then passed the FSM test but clogged a few days later when i noticed a gas smell around and in the car. i removed it again and it failed the FSM test so i shot carb cleaner in each of the ports and blew it out again a few times. it's been working well for a few days now.

despite a thorough cleaning, the EGR must have a pintle shaft leak because the engine was a little rough at part throttle until i disconnected the EGR. i would get another but think they're cost prohibitive. i think emissions control parts should be more affordably priced to encourage people to keep those systems functioning properly. in the meantime, this EGR will remain disconnected.