P0440, P0405/0404, MIL insconsitently on

[koine2002]

Hey there. I've done a search of the forums and I can't seem to find an answer. I have a 2001 Impala LS (3800, no mods). I've got just under 145k miles. I purchased it in 2008 at 87k miles from a family member who took excellent care of it. I've kept up with all of the scheduled maintenance.

Anyway, a few months ago my MIL came on and it pulled a p0401 (low EGR flow). I was prepared to take off the throttle body and clean the port. However, for good measure, I had my mechanic run his own scan (at nocost) when I had him replace the radiator a week later, and the 0401 was gone, but it was replaced by p0405/0404 (various EGR circuit/position malfunctions) along with a pending p0440. He suggested I start with a new EGR valve and replace the gas cap. He cleared the codes, I replaced the gas cap, and they stayed off for about a month until last week.

The MIL is not consistently on. It has shut itself off and on a few times between the last lighting and now. It was off for a few days until a week ago when a p0440 fault was detected with nothing else. It turned itself off a few ignitions later. It activated two days ago, and I scanned yet again today to verify my codes before I attempt repair this weekend and found p0404/0405 and a pending p0440 with the MIL set to on. I tightened the gas cap for good measure (it's a month old). I didn't clear the codes, but upon restart the MIL was off. The codes were still present in memory and the MIL was set to off. Now the EGR and EVAP systems went from ready to not ready (with all others being ready). I have inspection due at the end of May (Texas allows 1 not ready--and only in 7--out of 254--counties does this even matter) and want an idea of what to do next, both for inspection and ensuring that my car is in good working order.

As I'm getting a different commuter/errand vehicle (a 150cc scooter), this car will be largely pleasure/rainy day/pick people up status, but I'd hate to get caught by Dallas PD with an expired inspection.

[maxwedge]

When the codes are cleared some monitors can be slow to come online as there is a specific drive cycle to attain this, the evap system does not come into play unless you have between 1/4 to 3/4 tank. 440 is a vacuum leak somewhere in the sealed evap system, many things can cause this, a smoke test is the most common method for testing, unless a cracked hose or rusted tank filler is apparent.

[koine2002]

Thanks. I actually found at least one of the causes. The hose going from the fuel pressure regulator to the throttle body had a crack in an elbow. I discovered this in removing the hose to pull the throttle body (the egr ports were clean by the way). I also discovered that the rubber connector that connects the purge valve and the fuel pressure regulator hoses to to the throttle body had significant cracking. I've replaced the fuel regulator vacuum hose and have done a temporary fix on the rubber connector until I can find another. The EGR valve has been replaced so I'll see if any codes popup from that.