Thanks for the very good write up. Your findings are the same as mine.

 

As long as the STFTs are still working you are fine. I capped mine off this morning to see if it helps my issue I have. It is acting a little like it has a vacuum leak but I have triple checked everything and cannot find any leaks. I even washed the whole car yesterday and water got all over the areas that would be leaking. I started the car and I popped the hood and I could not hear any sucking sounds like you would normally get with a vacuum leak with water around it. Worth a try. I hope it helps.

 

I just threw the Low Purge Flow code yesterday just daily driving the car, not ragging on it or anything. And I twisted that little black cap just a little bit (less than 1/2 of a turn), but I'm going up to the dealer Monday to have them check it out/replace the solenoid for me hopefully.

 

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okay, so i get the capping part on the soleniod. but what about capping the line? doesn't the engine need to vent to pressure off? if you cap the line, wouldn't it be bad for our car?

p.s. should we also remove the charcoal canistor too?

 

I put a cap in the line too, though you can't see it in that pic. I later removed that section of line you see there and plugged the other section leading to it.

There is a vent solenoid for the fuel tank connected to the charcoal canister. Any pressure should be equalized through the vent, like it normally does.

As far as removal of the whole canister, that's something I'm interested in looking into, but haven't much yet. I'm thinking right now that it may not be easily feasible due to the fact that that vent solenoid is connected to it. You'd basically have to remove the canister and relocate the vent hose/solenoid directly off of the tank somehow.

I spoke with Vince today about possibly bypassing the Evap System check coding, so you won't throw a CEL and keep LTFTs. I'd like to test it and play with it a bit more to know what the best long-term option would be versus the benefits gained, as well as if there were any other issues with the evap system that were originally causing my issues in the beginning.


Just speculation:
I thought about it and I'm not so sure right now some of my reliability issues weren't caused by an issue with this system. When my original AFRs would initially swing rich, the ECU would pull fuel, and then it would swing very lean at times and stumble. If I happened to hit the throttle during that lean period (unknowingly) I'm not so sure it wasn't causing some of the bad knock that may have been the beginning of the end of my #1 piston. I remember hearing some bad knocking come from that side of the engine on one particular occasion. There was no other reason for knock that particular time, as I wasn't even at WOT, but I did suddenly start adding throttle to pass a truck (medium throttle at the time of knock). It sounded really bad and I immediately let off. I may be completely wrong about the cause of the knock though. It just seems like a very opportune time for knock to happen, and it's knocked on its own during some of those lean stumble times too at light throttle. That's part of why this mod makes me feel so much safer as far as engine reliability. It feels so much happier and the AFRs have been great, with no erratic swinging like it used to.

 

^so stamina, what you are saying is that i can safely cap the line too right? since there is another vent somewhere in the system for the gas tank.

 

Yup... that's what I'm saying. The canister/fuel tank is ventilated through a vent solenoid.

 

so when i disconnected the hose yesterday, the hose has this strong gas smell. so is it good that i disconnected the hose? since no more gas fume entering my intake manifold?

 

After about a week of the cap mod I finally got this code. It makes sense because the car is right, and it caught on to what was going on. I'm going to try getting logged to see if LTFTs are still functional with that code thrown.

I never smelled a super strong gas smell with mine, but air-gas vapor is what goes through that piping after all, so a gas smell makes sense.

Currently I've got the solenoid capped and zip tied, the evap line length going from around the battery's location to the solenoid disconnected, and the remainder of the evap line plugged with another cap. It shouldn't cause a problem unplugged, but I just don't like the idea of a line openly emitting fuel vapor beneath my hood like that, so I plugged it.

 

stamina, you got a code with the cap mod? that sucks, it means that i will get the code soon too.

 

Yup, definitely disabled that thing with hpt.

 

could we use a resistor to get rid of the code? actually, what is the ohm? so i can just hook up the soleniod with a resistor to get trid of the code.

 

You could dummy out the solenoid with a resistor I suppose, but you will still trip the low purge flow CEL unless you disable it with HPT, ect.

 

okay, mine car didn't throw any code yet. so i know stamina cap the line that goes to the soleniod, did you cap yours?

 

Yes, or you will have a vacuum leak every time the solenoid opens. I also covered the end of the purge line for now. Might remove the line later.

 

no no no, i did cap the soleniod, but just want to know if you cap the purge line. but i know you did now. mind to show me some pictures, please?

 

Nothing to see really, I put a cap on the solenoid like Stamina did and taped over the end of the line for now to keep dirt out. Also disabled the Low Purge Flow code with HP Tuners.

 

okay, when you say disable, is it the same to use my superchip to clear the code? would the cel come back on if i use my superchip to clear the code?

 

Clearing the code is not the same as disabling it. HP Tuners let you change the way each code is programmed. Once disabled it won't come back. Clearing it only resets it temporarily. It'll show up again.

 

okay, thanks i am broke. hope my cel doesn't come on.

 

I had an erratic idle and occasional power hiccups in WOT like for a few months now. I thought it was the winter gas or cheap gas. After I disconnected the solenoid yesterday it was like night and day. When i plug it back in at idle the engine makes a thud or knocking sound and vibrates more. I drove around some with it unplugged out to where I work and back to see if there where any differences I'd notice. When I first bought the car the coolant temp would stay around 199 while driving. For the last couple of months it has been hanging around 203-205. Yesterday with solenoid disconnected I noticed the temp was back down to 199 when the day prior driving to the same place the temp was 205. Weather was cooler yesterday than friday. Has anyone noticed a difference in coolant temp? I don't know alot about cars but the car didn't feel right the last few months and now it runs alot better. I am going to take it in to the dealer and try and get a new solenoid put it. Hopefully GM figures this out soon. The sound it made when i plugged it back was bad. I work in an electronics repair lab so I'm going to take the old solenoid and run it through a few tests save the data and compare it to a new one.

 

I took the solenoid into work and it seems to be working perfectly fine. It opens just above 6vdc and closes again around 4vdc. I read 22 ohms across it. It didn't seem to stick when i fluctuated the powere on and off. Whithout a new one to compare to this is the best I can do right now. If someone else wants to check theirs just hook a 9v battery to the solenoid and try and blow through it. Again I don't know a whole lot about cars but could there be something else wrong that disconnecting the evap purge solenoid would correct somewhat.

 

This is good information. Thanks for looking into it.

When we've been disabling the Purge Solenoid in whatever form, we're isolating the whole system from the engine. The Purge Solenoid is simply the "gate keeper". As you pointed out, there could be something happening somewhere else in the system that's causing this issue.

In my case, the new valve helped in some areas, but didn't completely solve it to my liking. A friend of mine had their purge solenoid replaced on a hunch from the tech and had no improvement at all though, so this compounds the mystery.

What's hard to tell is whether the problems are the same problem or if they are problems with different parts of the system that end up having similar effects. We at least know it's something to do with the Evap System... but what exactly is still yet to be found...

 

I have my solenoid dissconeted and now at idle I can smell gas coming from the hood so this is a bad thing but the car dosent act right with that damn solenoid plugged in

 

Did you unplug the evap hose and not cap the hose? I have not experienced any weird smells.