Series 2 3800NA Grand Prix GT fuel question (Page 1/1)
Rallaster OCT 04, 10:44 AM
I just recently bought a 2002 Grand Prix GT with the 3800NA and the fuel gauge seems to be stuck in the full position. I plugged in my OBD2 scanner on my way to work this morning and attempted to pull the fuel level off of the ECM, but the scanner I have doesn't see that information. It does, however, see the fuel flow rate(in Gallons per Hour) and what I saw confused me a bit. According to my scanner, the fuel flow rate, with the cruise set at 65 on flat, smooth roadway, is between .7 and 1.1 GPH. I don't have an option for a 'per cylinder' break down, so I'm assuming that is a total system flow rate. If my math is right, that's around 60MPG, and that seems REALLY high to me. What am I missing, because that can't be right.
Xyster OCT 04, 11:13 PM
Could you have been coasting down hill and not realized it? CC closed the throttle plate, decreased demand etc etc and it just happened to be when you were sampling the computer?
Rallaster OCT 04, 11:29 PM
No, it was on level roadway. WOT pulling a hill only peaked at 3-ish at 75. Going down hill it reports flow at around .3.

[This message has been edited by Rallaster (edited 10-05-2012).]

phonedawgz OCT 14, 12:44 AM
The way your scanner/computer figures fuel flow is by estimating it from the injector pulse with (duration) and the number of injector pulses per second. Don't get too excited about your calculated MPG. You can however use it for a comparison to other flow calculations while driving.
Rallaster OCT 14, 09:04 PM
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Reading from today. 3 mile stretch of straight, level highway, cruise set at 60MPH. If my math is right, that's 26 MPG. Right? I'm going to log my trips this week and see if I can get some consistency and verify on the next fill up.
86SE4ME OCT 20, 04:41 PM
Check into the fuel pump. I had a 2000 Grand Prix that the fuel gauge cut out on and that ended up being the problem in mine. not 100% sure that's the problem with yours but its something to look into.
86soon3.4 OCT 21, 10:09 PM
My wifes 2001 Gran Prix GT 3800 NA gets 24-27 on the highway. She did get 32 MPG on her trip to NY this past summer thou.

Steve
Rallaster OCT 23, 01:36 PM
I just did my 3rd fill up and fill up 1 averaged 21.8 MPG, fill up 2 (exact same route, driving style, etc) 24.7, and 3rd fill up(mild variation in route) 25.6. I'm very happy with my economy.