I've been disappointed with my V6 Getrag gas mileage. Measured at 16.1 and 17.x on recent >200 mile runs. Very bad. CEL not on. Hooked up forscan and found really bad numbers, 99.22% on STFT for bank 1 and bank 2 sensor 2s. Also have 'error' on fuel system 2. Gotta run again and log O2 numbers on sensor 2s. Measured at idle only thus far. OBD2 shows only 1 DTC, P0442 but forscan shows 9 DTCs!?. The P0442 has been there for a couple years. It indicates an EVAP System Leak Detected (Small Leak). I've been unable to find this problem but car can pass CA emissions test with this indication so I stopped trying to fix it. Now gotta diag and fix this issue. Can't afford gas anymore. Any help is appreciated.
Poor gas mileage. Bad short term fuel trim
- Thread starter heyjewel
- Start date
So I ran it again and logged all the O2 sensors. All were good. Read a little and the 99.2% that is reported is a 'default value' if something's wrong. But what is that some3thing? Could be O2 sensors but they check out. Could be MAF? But I have problem only with one bank so that's probably out. Cat for bank 2 could be it but how to check? Other issues? Anyone have a feel for what might be wrong? Joegr?
FDR
Dedicated LVC Member
How long have you had the car? How's the exhaust smell? Any idea when the ignition coils were last replaced? For that 200 mile run, what kind of driving was it? One drive or multiple? 200 miles at 55mph (where the EPA figure comes from) is different than 200 miles at 80mph or 200 miles in hilly country roads. My V8 gets 25mpg at 70mph with no playing and the V8 is pretty closely rated to the V6 for highway. But if you did anything other than cruise at a steady legal speed, mpg takes a hard hit. For the cat, if the exhaust doesn't smell awful and neither turn bright red while driving, I don''t think there's much you can do to check them. If they were clogged, a cat inefficiency code should pop up soon enough. Are you sure the code is P0442 and not P0422?
I agree, may as well post the other 8 DTCs, but they should just be ABS/SRS/accessory type codes and irrelevant to the fuel economy. Forscan isn't going to find extra P codes since that's the whole point of OBDII - the B and C codes are just tagging along for convenience of the existing interface. There's a number of lingering B codes too, namely from battery disconnects or slightly weak charges.
I agree, may as well post the other 8 DTCs, but they should just be ABS/SRS/accessory type codes and irrelevant to the fuel economy. Forscan isn't going to find extra P codes since that's the whole point of OBDII - the B and C codes are just tagging along for convenience of the existing interface. There's a number of lingering B codes too, namely from battery disconnects or slightly weak charges.
I will post the others when I run it again today. Forscan did not save previous runs. I ordered the car new. Wanted the 5speed. Wish it was teamed with the V8. Exhaust smells like exhaust. Igniton coils replaced 10000 miles ago. The drives I took were 1/2 stop n go and half up/down highway hills.
So here's a couple screen shots of today's run:
Note the error on fuelsys2.obdII; the 99.22 on both O2S12.STFT.OBD and 02S22.STFT.OBD. The 'NO' for cat eval, ctr bottom. The 323dtc lists the dtcs. B1869; P1000; P0442; P0442-p; U2008; u2005; u2003.
milehighmikey
Dedicated LVC Member
Bank 2 is left side, correct?
Check your plugs in that case, look for one or more that are wet, just to rule out an overfueling issue.
It is starting to sound like possible O2 upstream sensor issues, if we do have them. If you have an infrared thermometer, check your cats for consistency.
If you need a parts car, mine could make it there, lol. I am done with mine. It is still registered until 30-jun.
Check your plugs in that case, look for one or more that are wet, just to rule out an overfueling issue.
It is starting to sound like possible O2 upstream sensor issues, if we do have them. If you have an infrared thermometer, check your cats for consistency.
If you need a parts car, mine could make it there, lol. I am done with mine. It is still registered until 30-jun.
ajv8
Well-Known LVC Member
those are secondary trims with a default value of 99.92. the ptec was capable of using downstreams to do sub-trims but it wasn’t used
on newer cars you’ll see p2096/97/98/99 associated with the downstream trim
on newer cars you’ll see p2096/97/98/99 associated with the downstream trim
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Yeah I looked that up and 99.2 is the default value. Means nothing. OK so I still have error in fuel sys 2 and no cat test on one side or the other. Thanks for info. What is ptec?
milehighmikey
Dedicated LVC Member
Good luck. How long have you been running the proper fuel now? Running regular would retard timing somewhat to prevent detonation, but I don't know how bad that would affect MPG efficiency.
I've run regular for a decade or more.
04_Sport_LS
Dedicated LVC Member
What 02 sensors are installed currently? A number of threads on this forum suggest NGK sensors. I have no issues with NGK.
Bosch are problematic. So are most others.
Bosch are problematic. So are most others.
Dunno. Next time I'm under there I'll look.
Some more mpg info. Cleaned the MAF sensor. Ran two tanks of Chevron Supreme instead of el cheapo regular. Took her on a 200+ mile round trip on highway. Got 21 mpg. That's about as good as she's ever gotten. Going to keep an eye of her mpg.