[s-cars] I want my MPG

[David Forgie]

Teddy:  The G62 isn't that expensive and it's failure causes the ECU to think the engine is cold,
leading to rich conditions, as you describe.  It's easy to change so I would say do it.  Can't hurt.

Certainly,  you could have a leaky injector or something else, but I would put money on the G62.
As for a cold start valve, AFAIK, we don't have one - I believe it's the ECU controlling the duty 
cycle on the injectors with the aid of  the G62 signal.

Good luck.

Dave F.
----- Original Message -----
From: Theodore Chen <tedebearp at yahoo.com>
Date: Wednesday, June 11, 2008 10:16 pm
Subject: Re: [s-cars] I want my MPG
To: David Forgie <forgied at shaw.ca>, s-car-list <s-car-list at audifans.com>

> 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.