Reply To: Might stump ya! 08 suburban 5.3l rich and evap

[Will Parker]

Well we FINALLY seemed to.manage to dig up the culprit!! I mentioned i replaced the purge valve solenoid about 6 years back. Well over the past year I’ve taken the truck in a few different times for this rich issue and each time we found other problems like my cats were plugging up, o2 sensors going bad, leaking injectors etc which would obviously contribute to those codes but never seemed to fix the issue. Now the vent valve was done in January (had em look it up today) I said previously about 6 months ago so a bit longer. But no other evap codes til this newest p0455 large leak. So I let it sit til I brought it back in and we finally uncovered the issue. The purge valve was sticking open. Not all the time as it tested ok on previous checks but this time it had gotten bad enough to show its ugly face and they had me go into the bay to talk to the tech (he is the only 1 who works on my stuff there and he knows me and my vehicles we got a good relationship) and showed me with the smoke machine he had the rest of the evap system closed off and all that tested out just fine but this would stick open. It would close randomly when not supposed to then go back to wide open and that can easily cause a really rich running condition as the unmetered vapor flowing in is at odds with the rest of the readings and the o2 sensors are saying its too much gas. Since it technically didn’t fail it didn’t set its own code like it did before. I got about 50k miles out of it. Got to thinking that even though my LC9 is a flex engine I’ve never run e85, BUT regular gas (and I only ever use top tier rated gas) is still up to 10% ethanol. Gas dont absorb water but alcohol does. And flowing thru there as a vapor that can cause ut to gum up and cause corrosion. Jason confirmed this actually as he pointed out that over the past year he has noticed more and more of these failing on various vehicles. Ive thought about adding some water remover to my gas now n then to try and combat the issue. But gonna out the one on here in a bit and drive her around awhile see how she does. I do appreciate the input Richard it did help!