Hi All,
Fairly new to the forum but I've been reading it for a couple of months now. Has anyone noticed carbon build up on at the exhaust tips, poor gas mileage, and a floating tach needle when the clutch activated?
My first tank of gas was 87 grade from the dealer and I got 28+ mpg. I filled up with 93 the next two tanks and my mpg has been 23.5-24 for each. I was rinsing the car off last Wednesday and noticed lots of carbon build up in the tips (looked like a stove pipe!). Sent an email off to the dealer today and will schedule a check up to see why she's running so rich. Has anyone experienced anything similar? I took delivery on my GXP on 15 Jan 2007, and haven't been hard on her at all. Broke in per GM's recommendations. I have around 950 miles currently.
I haven't had that particular problem with carbon build up but two months ago I did notice a rich fuel smell... (like in the old days when the carb's mix was off.) The dealer recommended that I have the fuel injectors cleaned. I was @ 20,000 miles.
Location: The avatar shows my motivation to work .... Work takes place in Houston, Republic of Texas .... Motivation takes place in CA, NV, UT, CO and similar locations.
I don't know if this would help, but I'm sure it won't hurt.
You could disconnect the negative cable to the battery and leave it off for at least half an hour, maybe an hour is better, but all night doesn't hurt either.
When you reconnect, you'll have to reset your clock and radio stations. But see if the car doesn't run a whole lot better. You might be pleasantly surprised. This resets the ECM to whatever the settings were from the last flash, which means factory settings if you have never had an ECM retune, or the retune settings if you have had a reflash.
Others on the Forum know which fuse(s) (?) to disconnect just the ECM.
.
__________________
Her name is MariSOL
VIN 6Y101319, delivered 10/15/05. 71,923 miles.
You did say GXP ... Right? So yes what you are seeing is normal and it is lovingly called turbo soot Not sure about the mileage but I get between 22 & 25 in mixed city driving ... more like 25 if I stay out of the boost and more like 22 when I am hitting it hard. See 28 or more for pure highway mileage. HTH
__________________ #118042 11/18/06 GXP Mean Darkside loaded wo On-Star
MODS: ED IC Pipes, Dejon IC, Magnaflow Catback
~~~~~~~~~~~~~~~~~~~ Pontiac builds excitement... Saturn has rethought it's image...
The time has come for the enthusiasts... NASSOA
Founding Member - Recording Secretary - Northeast ~~~~~~~~~~~~~~~~~~~
Hi Wamin,
Mike's putting you on the right track. Like it or not the sooting is characteristic of a turbo and caused quite a stir around here when the GXPs and RedLines were first delivered to folks unfamiliar with this fact. I haven't heard of any GM engineers being strung up lately, so I think it's fair to say that between the "soot" and the "ticking" (don't ask, but search if you must ) the lynch mobs have finally disbanded. Your report on mileage isn't typical at all however. Premium fuel (91 or better) is recommended and many of us use 93 if it's available with our GXPs and Redlines. The higher octane results in consistant reports of better mileage here generally. I'd be patient if I were you and continue to monitor your mileage to see if it improves with continued use of premium gas if you plan to use it. Otherwise it may require a check with the dealer 'cause it's at odds with others' performance and there may be a problem. Gizmo's idea can't hurt, I'm not aware of any empirical information to support improvements however many people anecdotally report them here after performing his routine. I did it and noted differences right away. Good luck with your car and with sorting things out.
Thanks to all for their reply, I feel better knowing the gas mileage is about where it should be. I'll still have the dealer take a look as the tach needle floats more than it used to and my driving habits haven't changed that much (most of my drive is 45 one way back and forth to work) Yes, my GXP is a commuter!, and I love it!!!
~~~~~~~~~~~~~~~~~~~ Pontiac builds excitement... Saturn has rethought it's image...
The time has come for the enthusiasts... NASSOA
Founding Member - Recording Secretary - Northeast ~~~~~~~~~~~~~~~~~~~
Location: Rosamond, CA - Home of Willow Springs Raceway
Actually the soot is not from running rich. The GXP runs lean. Direct injection allows that. But as a result, there is more soot. Beau had a better description, I'll try and find it.
__________________
2007 Cool GXP with Darkside Top, 5 spd, Ebony Cloth, Monsoon with Single CD, Sport Pedals, XM, A/C
Mods - Solo Street/Race Exhaust, K&N Drop-in Air Filter, EDAL
Location: Rosamond, CA - Home of Willow Springs Raceway
Here it is.
Quote:
The thing about the sooting actually isn't running too rich exactly, its running too rich for a direct injection application. Its weird but not the same.
For instance crusin around in the car, your likley to see 15:1 + A/F : O
Stoich for a Direct Injection car is ( Im wrong about this but I forget the Lambda value ) ~ 15.5:1 - 16.0:1 + that = port injections 14.5:1
So what happens is there is a weird line, and I read some info on this and it was a a concern of GM's. They had a choice of getting the motor to soot, or cylinder wash. So they went with sooting. Its not too rich, they just didn't want cylinder wash to occur, that would be catostophic for any motor. Fuel + oil = no motor :}
__________________
2007 Cool GXP with Darkside Top, 5 spd, Ebony Cloth, Monsoon with Single CD, Sport Pedals, XM, A/C
Mods - Solo Street/Race Exhaust, K&N Drop-in Air Filter, EDAL
Not sure about the mileage but I get between 22 & 25 in mixed city driving ... more like 25 if I stay out of the boost and more like 22 when I am hitting it hard. See 28 or more for pure highway mileage. HTH
) the lynch mobs have finally disbanded. Your report on mileage isn't typical at all however. Premium fuel (91 or better) is recommended and many of us use 93 if it's available with our GXPs and Redlines. The higher octane results in consistant reports of better mileage here generally. I'd be patient if I were you and continue to monitor your mileage to see if it improves with continued use of premium gas if you plan to use it. Otherwise it may require a check with the dealer 'cause it's at odds with others' performance and there may be a problem. Gizmo's idea can't hurt, I'm not aware of any empirical information to support improvements however many people anecdotally report them here after performing his routine. I did it and noted differences right away. Good luck with your car and with sorting things out.
Linear Mode
