Lost power in an '04 XG350L
 

Recently the "Check Eng" light came on in our 2004 XG350L. It stayed on for
a couple of days, and went out. Right after that, the car would hesitate on
acceleration from a dead stop and sort of stumble as if it was not getting
any fuel. The car has 32,297Mi on the clock and has always been treated with
love and care. I only use Union 76 (Top Tier gas) or Conoco (same company)
87-octane and usually tank-up from the same service station. Service has
been done religiously by the dealership since the car was purchased. My wife
took the car in today and they found a diagnostic code of "P0446" - a code
that is NOT in the manual. The tech called the TECH LINE and was told to
clear the code and do EVAP test 2x. The car passed both times. He then
purged cylinder connectors - turned out OK at this time. No other codes
found. Then there was this sort of cryptic code at the end of the invoice -
"39466RPO .3 N15 C15". So, any thoughts?


--

Carl


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Jackson: Carl & Karen
E-Mail: cajo20@comcast.net
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Re: Lost power in an '04 XG350L
 

Your car's evaporative emissions system tests itself with engine vacuum.
There's a valve on the charcoal canister which closes and a purge solenoid
on the engine which cycles to vacuum the system. The code P0446 typically
means that there's too much vacuum in the system during non-test times.
This usually means that one of the following has occurred:

The close valve (the one on the canister) stuck closed, causing the system
to not be able to vent properly.

The purge valve stuck open, causing constant purge (and more vacuum than
intended).

There is a restriction in the venting of the canister. This could be in
the canister itself, in the vent filter, or a clogged hose.

The fuel tank pressure sensor was inaccurate, causing the computer to be
fooled into thinking there's too much vacuum in the system.

I've seen all of the above. What's worse, running the evap test may not
make the code reoccur. I'm surprised tech assistance advised him to
diagnose the problem in this fashion.

Basically, what he did, was check the system the way they requested as
well as check some of the connectors to verify good contact, and didn't
find any problems.

If there's a problem still there, you check engine lamp will likely come
back on within the week.

39466RP0....
 

That's a warranty labor operation code relating to the canister purge
valve.

There's a huge TSB pertaining to P0446 and a flowchart within to diagnose
it. I see it a lot at work (dealership) and usually it's a canister close
valve, purge valve, or tank pressure sensor that's kicked the bucket. Your
light will be back on soon since they didn't find and replace the faulty
component judging by the labor op code above. It can be tricky because the
various sensors and valves can intermittently glitch. If you head back with
a P0446 again, point them to TSB 04-30-001.