[s-cars] I want my MPG

[Mark Strangways]

the TPS has an idle switch in it as well.
This would allow it to idle fine, yet once off the idle switch the ECU could 
think that the throttle plate is open fully or to a large percent.
The Bentley may have a test for it, which might be just as easy as testing 
the resistance throughout its operational range.

One thing the motronic manual suggests is that if the temp sensor fails, or 
the ecu thinks its failed, it will default the water temp at 70 C. This 
would still cause poor mileage, and an overly rich mixture but I am not sure 
it would be as dramatic of a change.

IMHO, even if something is supposed to throw a code, don't expect that it 
will. Test the part and don't rely on the ECU to point it out. I have solved 
more issues with sensors problem with out codes being tossed.

I will be eagerly anticipating your results :-)
BTW, I have a GT30R... so I really hope that the turbo is NOT the cause of 
our issues

Mark
----- Original Message ----- 
From: "Theodore Chen" <tedebearp at yahoo.com>
To: "David Forgie" <forgied at shaw.ca>; "s-car-list" <s-car-list at audifans.com>
Sent: Thursday, June 12, 2008 1:16 AM
Subject: Re: [s-cars] I want my MPG


> 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.
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