[s-cars] I want my MPG

[Theodore Chen]

thanks.  mark suggested using vag-com to see what the ECU thinks the coolant temp is.  i have a vag-com, but didn't think of using it.  duh!

from your post at the link you gave:
If the AAN G62 coolant temperature sender is broken, the AAN ECU may
"think" its cold out all the time, leading to higher duty cycles on the
injectors and, therefore, rich runnng conditions (which, by the way,
can burn out the catalytic convertors) and poor fuel economy.

that's exactly what i'm thinking.  the shop thinks it's my MTM software or the turbo, but i'm doubtful.  the car has had the MTM software for at least 8 years and passed smog easily.  the GT2871 is new since the last smog check, so it's possible, but the test is at idle and 2500 rpm, no-load conditions.  i highly doubt the software is calling for boost at 2500 rpm with no load.

shop says spark plugs have been changed, oil has been changed, timing has been checked, coils checked, cats replaced, and it's just barely not passing.  could be oil leaking from the turbo, but oil consumption is about 1 quart in 3000-3500 miles, which doesn't strike me as being particularly high - especially since i know the oil drain nipple on the bottom of the turbo is leaking (i can't get a wrench on it to tighten without taking the turbo out so i've just let it keep leaking slightly).

other possibilities i'm considering:
leaking fuel injectors
leaking fuel pressure regulator
bad throttle position sensor (but wouldn't this cause roughness?)
stuck cold start valve (but wouldn't this cause roughness/stumble?)
ignition coils (even though the shop said they're OK) or POS
evap canister purge solenoid (would this set a code?)

idle in my car is smooth, and there's no stumble.

-teddy


----- Original Message ----
From: David Forgie <forgied at shaw.ca>
To: s-car-list <s-car-list at audifans.com>
Cc: tedebearp at yahoo.com
Sent: Wednesday, June 11, 2008 8:16:45 PM
Subject: [s-cars] I want my MPG


Teddy:  It could be the G62 temp sensor at the back of the head, not the temp sensor in the heater-hose T (that one is for the climate control).  Info about the G62 is available at:
 
http://forums.audiworld.com/s4s6/msgs/148742.phtml
 
Dave F.