For months i've been battling a lean code on my box. I thought it was my catch can set up, so I removed it. It came back, I thought it was the MAF, I replaced that (after cleaning didn't work), I thought it was the gaskets to my TB spacer, I replaced those, I thought when I pulled the intake manifold for paint I pinched the gasket, not it, I thought it was a leak in my braided hoses, I returned all hoses back to stock, not it. Today at my wits end, while staring at the engine, with scanner in hand (watching my fuel trim max out both long and short term), I was grasping at straws and started pinching hoses with pliers. When it came to the hose from the purge valve to the TB, all the readings went to normal. I have a damn EVAP system leak!!

Does anyone have the input test data for testing the EVAP system valves with a DMM?

 

P.S.
does anyone know if the EVAP will throw a CEL if I block off that line for a bit.. it appearently doesnt realize there is a problem now..

 

Start checking your fuel system - gas cap seal - all the junk under the trunk - left rear wheel well filler hose and vent hoses.

 

yeah.. I think its the canister 2 way valve or the vent shut valve.. I just want to do the check,
but I need the specs on what i'm looking for.. my car occasionally dies after fueling as well, I'm sure its all related.
On a side note, I just drove around for 40 miles with the hose disconnected
and the port capped. I lost my fluctating idle, and vibration I had before.
No CEL as of yet. I'm sure it's just a matter of time, but we'll see...

 

I'm assuming the code you are battling is a P0171. The EVAP purge valve, which I believe is the one you pinched the hose for, works on a duty cycle, it is either off or pulses (open/close) when ECM commands it. If your scanner can active test it, it should constantly click & system pressure will eventually drop to 762mmHg-a. And yes the EVAP system will generate a CEL depending on the malfunction, P0441 or P0446 more than likely in your situation. The lean code more indicates an air leak after the MAF where the ECM sees a lean reading but can't account for the air because its not passing the MAF.

 

The code is for system too lean, bank 1.. I forget the number. It is recieving air passed the MAF via the EVAP system. I just pinched the line at the EVAP canister, and again the leak dissapears. This does happen, fuel contamination takes out the valves, they get stuck open (my case) or closed. The system when requesting an EVAP purge event is purging, and not detecting a fault. I unplugged it yesterday (the purge line) and I got a CEL today for evap insuff. purge. This tells me it is working. The leak is either the bypass, two way, or close valve at the canister, I believe the purge valve is not completley closing, allowing the air through at all times. I think maybe I keep reseting the PCM before it can meet the criteria for an EVAP system code. These are usually multi trip DTC's. I just would think it would throw an EVAP specific code, rather than the system lean code. Either way it is at the canister, and possibly the purge valve. I emailed the service manager at my dealer about clearing me for warranty. My car has had alll systems modified in some way, but not the EVAP. Hopefully, they will fix me. That canister is pricey!

 

Is that system part of the 70-100k 7 year emmission system that is covered with longer coverage per government law like the cat etc.?

 

yes, but i'm throwing a lean code, the dealer sees I have a TB spacer, I have removed the intake, and etc.,. even though I showed up with a scanner and tools and showed the guy that the leak goes away when I take the canister out of the picture directly, they say I modified the system (again nothing I have done affects this system).. found one at a junk yard through a buddy for free, so I will be trying that out ..

 

anyone find a solution to this problem? my tc is having the same problem with its purge valve, causing me to run lean as per spark plugs being white.

 

one thing I have seen, is that when an intake is installed, sometimes the purge valve lines were put back on reversed
(the hoses reversed on the 2 "nipples")... it WILL throw a
lean code for this, and nothing else.. check that.. or a
vacuum leak elsewhere..

the purge valve is stuck open, or..

the evap canister has a leak (like me)..

 

have 06 xB with 122,000 miles on it. I'm running a consistant P0171 code along with the P0441 and P0455. cleaned MAF and spark plugs look little white. drives fine on highway with good gas mileage, but when I come to a stop sign or park it, idle drops and throws the code.