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Pontiac Grand Prix Fuel System

dribs15dribs15 Member Posts: 6
edited March 2014 in Pontiac
well my heavy foot city mpg is up to 13.2 at 1100miles-would love to end up getting 15+...maybe in time.

also, i travel on rte 295 in s. jersey same stretch every day when i go to work and few times i've tried cruise control at 80mph (b/c of the posts seen here), sometimes DOD has definitely kicked in b/c i'm getting at least the upper 20's and maybe higher (can't remember) mpg, while other times it's lower, but i've noticed more wind resistance.

chats1 sorry about your hum, but mine is not loud and goes off as soon as you turn the car on too...maybe it is onstar.
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Comments

  • rayainswrayainsw Member Posts: 3,192
    “also, i travel on rte 295 in s. jersey same stretch every day when i go to work and few times i've tried cruise control at 80mph (b/c of the posts seen here), sometimes DOD has definitely kicked in b/c i'm getting at least the upper 20's and maybe higher (can't remember) mpg, while other times it's lower, but i've noticed more wind resistance.”

    In the interest of science (ahem) I tried an experiment this AM on the way in to work.

    Since the traffic was (much) lighter than usual, I was able to set the cruise at 80 for a few minutes. Twice.

    Although there is no “DoD On” indication like there is in the Impala SS, my observations are that even the slightest incline \ upslope (Interstate upslope on I85 just north of I285 and just south is likely less than 1%) will dramatically reduce the instant MPG – from 28 – 30 on level or (very) slight downslope to below 20 MPG.

    As always, YMMV.
    - Ray
    Wishing my every commute could be this light, traffic-wise . .
    2022 X3 M40i
  • tjrgxptjrgxp Member Posts: 2
    Also drive 295. New GXP 2006. Have gotten 25 mpg on 295. Have averaged near 23 in a week with mixed hwy/city driving. Have gotten as low as 18 mpg also. Car is black and is very hot looking. Two problems so far - 1) Thermostat bypass hose on top of engine was gashed open by the pulley (maybe a poor factory installation). Dealer fixed and repositioned. Hose was hard to get. Came from lansing Michigan. Was without car for three days with onlt 1000 miles on engine. 2) No automatic dimming rearview mirror is a disappointment and a downgrade from my 1999 GTP. Owners manual says it is an option. Well, what model do they put it on, if not the GXP? No mention of that option in the book. Nevertheless, my GXP is all that they say it would be. Love it. Too bad GM is cheaping out without telling the buyer. Watch out for your bypass hose.
    Tjr GXP :shades:
  • bob97bob97 Member Posts: 16
    I also miss the auto-dimming feature – my guess is that it interfered with the microphone pickup for Onstar. But my biggest problem with the rearview mirror is how much of the front view it blocks.
  • sigfulsigsigfulsig Member Posts: 2
    The good news about the rear view mirror is that it takes up so much of the view that when I mount my GPS (Garmin Nuvi 350) under it, I hardly notice the difference. ;)
  • smallegansmallegan Member Posts: 10
    Does anyone know if there is a way to verify that your DOD is activating? I drive the GXP pretty hard and I am just wondering at what point it activates?

    -Ryan
  • dblducedblduce Member Posts: 58
    Ryan,

    I read that a good way to verify when the DOD turns on is to put your information display on 'Instant MPG'. That way, you can watch your actual miles per gallon usage as you drive. I have tried this on the highway. Normally it is around 19-24, but after a few minutes if the road stays level you can tell it has turned on because the MPG starts going up to around 30 or more. I think it has to be running at a constant speed for a set amount of time before it kicks on.
  • rmozolrmozol Member Posts: 124
    That's good to know. I always watch that screen, but probably not for long enough.
  • gxpjoeypgxpjoeyp Member Posts: 38
    I would like to know too,on the Impala ss and the monte carlo ss there is a dummy light that comes on the dash when it is running 4 or 8 cyl. why did gm put that light on those 2 models and not the gp gxp,after all they are the same engines.
  • rmozolrmozol Member Posts: 124
    I'm guessing because they made the GXP in 2005, and not the others, and didn't want to change the GXP's design.
  • pckeenanpckeenan Member Posts: 3
    I have a 2000 Grand Prix GT and have noticed a high pitched whining noise that increases at low speed accelerations. I've also noticed that when accelerating at low speeds, the engine drags/shutters.

    Not sure if these two are related or separate problems.
  • dsnowsdsnows Member Posts: 1
    I had a similar problem with a high-pitched whining noise when accelerating and worse when turning. My power steering fluid was low. I had the dealer add fluid and the noise has stopped. Good luck.
  • lilbkrboy89lilbkrboy89 Member Posts: 1
    my car is choking really bad when i floor it my car sounds like its dieing out and the rpms are jumping up and down and it kind of shakes a little its a 98 pontiac grand prix sc
  • pontiacwolfpontiacwolf Member Posts: 1
    I need a new MAF sensor. I was thinking with going with a Granatelli. Does anyone know any other performance brands that are good for a GTP?
  • ljm1667ljm1667 Member Posts: 1
    I recently have been having a problem with my grand prix that no one can figure out. about a month ago i started up my grand prix and it stalled out after about 7 seconds, it kept doing this so I had it towed to a local service center. I was told it was my fuel injector and regulator. Both were replaced and the car started. I took my car home and about an hour later I started it up and it again stalled out after a couple of seconds. At this time I now had the car towed to a dealer who had it for two weeks. They told me that my fuse box was bad and they replaced it. They guaranteed me that this was the problem. $1400.00 dollars later I got my car back. I was able to drive it for two days with no issues. Again I got in my car to go to work and it started up for a couple of seconds and stalled. I was thinking there was an issue w/ my security system but the dealer said that was not it. Does anyone know what could be wrong with my car. I have had no problems with this car until now. My pocket book is getting slimmer everytime it is at the dealer. Any suggestions on what is wrong with it would be greatly appreciated.

    thanks !
  • wufidowufido Member Posts: 3
    I need desperate help!!! 12.2MPG (yea some people think they got it bad with (20MPG) It was at 11.0 MPG before everything I'ved replaced, heres the list.
    1.Rebuilt SuperCharger
    2.ACDelco SparkPlugs
    3.Wire Set (spark plug)
    4.oil change every 3K (oil filter too)
    5.New PCV Valve
    6.New O2 sensor (before catylic)
    7.New Fuel Filter
    8.K&N filter and intake

    Anyone out that can really help. with any Idea Please EMAIL ME at Sol9586yahoo.com as you can see there has been alot of money invested and im not seeing any progress. 12.2mpg city / and 12.5mpg hwy. HELP!!! HELP!!! HELP!!!
  • mkeilymkeily Member Posts: 1
    Any ideas what the problem was? My 98 Grand Prix is in the shop at this very moment and the mechanics are stumped.
  • toolnuttoolnut Member Posts: 1
    Check the fuel pump resistor, a common issue on supercharged engines. Most likely it will run if you hold it floored, but a common issue.
  • jeff65jeff65 Member Posts: 1
    I just got my 200 GP GT back from the dealer after the same issue. It turned out to be the Theft Deterrent Module $560. They said their is no way around it. GM had a bulletin out that said the wires were prone to chafing. I hope this helps.
  • 2000grandprix2000grandprix Member Posts: 1
    hey bud, well i dont know if this is much help but my buddie was having the same problem. next time this happens to you un hook your battery for about ten miutes then put back together and see if it still happens if this works them it has something to do with your security system . thats what happend to my buddy grand prix ( i know it sounds stupid buy hey its worth a try )
  • johnny69johnny69 Member Posts: 1
    i just replaced the fuel pump and fuel filter in my 00 Grand Prix GT and it still sputters every once in a while when i drive it even does it when i drive down the highway it sputters any idea whats up? :cry:
  • bowerdhbowerdh Member Posts: 1
    Has anyone delt with the level indicator going from full to empty and not reading anything in between? looking at the part (fuel pump) the sending unit is a part of the pump. I am currently going through the ignition switch replacement due to the heater fan and the console going out (thanks for the info. on this site) and was courious if some one else has had similar issues.
    2001 gtp
    :confuse:
  • bigskidoggbigskidogg Member Posts: 8
    2000 gtp error codes po203 (injector circuit open cylinder 3) and po303 (cylinder 3 misfire) i think i need to replace injector # 3 and was wondering if anyone has gone thru this procedure? looking at the chilton manual it seems possible to do on my own i am just a bit confused on if i need to remove the whole fuel rail assembly or can i just pull out injector # 3 by itself without taking off the fuel rail. if anyone has any info on this it would be greatly appreciated.
  • susy93susy93 Member Posts: 1
    I am having problems with my 2002 pontiac grand prix. I lose acceleration on hills when i push the gas pedal the rpms go up but i lose acceleration. Today coming home I slowed to turn on to my road off highway and it died. I got it started after a bit and got it almost home but had to slow down and it died again. I was thinking fuel pump or filter? Any suggestions?
    Thanks
  • billybillbillybill Member Posts: 2
    Hey man, I've had the same problem with my fuel gauge. When I start my 2000 Grand Prix GT, the fuel gauge shows completely full but with in a few minutes of it running, the gauge drops to empty & the low fuel warning comes on.
    I purchased & installed a OEM GM sending unit, but it still did the same thing. A few weeks after that my fuel pump went out so I replaced it with 1 from Auto Zone which come with a sending unit attached. I was really hoping this would fix my problem but it hasn't.
    So for months now I've been keeping up with my mileage so I dont run out of gas, but this is getting very difficult as HIGH as gas is now.
    If anyone can let me know what I need to do, PLEASE HELP ME OUT & DROP ME A LINE.
    PLEASEEEE HELP ME !!!!!
  • lennixandloulennixandlou Member Posts: 1
    My wife has a 99 GTP, she has the same symptoms as your 2002. To make a long story shorter, I used to have a GTP of my own and that thing had one incedent where it wouldn't start..... took it to the sercvce dept installed fuel pump, regulator and it still wouldn't start.... finally I spoke with a vetran GM mechanic and he said it was the FUEL PUMP RESISTOR...... Indeed it was. Now my wife's car will start but it will die on occaision (non electrical) It is the Resistor again. Here is the kicker, the resistor is only on the GTP models and it seems like no parts stores can find it..... .GO TO A GM DEALER AND TELL THEM YOU NEED A FUEL PUMP RESISTOR, should be around 50 bucks and it is located in one of the fender wells inside the engine compartment. Can almost garantee thats what it is
  • mkchickmkchick Member Posts: 1
    My 2002 Pontiac Grand Prix GTP Supercharge was having some problems while driving this past week. It would cut out at 70mph then just kick back on or die. I would pull over and did not have any problem starting the car back up. I turned the AC off and anything else I had on and put the windows down. I notice the smell of nasty eggs. I knew it was my catalytic converter going out. I got on the phone and my husband told me that since the car was under 80,000 miles I was still covered it was just a matter of getting the car back to the dealership. I hauled it in on Saturday and get a call on Tuesday that my car would not start so they checked it and the fuel pump is almost gone. They said they had the hit the fuel pump just to get my car to start. They replaced the converter and I told them to not touch anything else. They wanted $850.00 tor replace the fuel pump. Can this really happen? Can my car go from starting fine to not starting at all? I am going to pick the car up so any one that has any advice I would sure appreciate it.
  • heavyphdheavyphd Member Posts: 1
    I have a 2002 GP GT. At 82500 miles I had a similar issue (I also had random misfires on the OBD II). Mine turned out to be a 'clogged' Catalytic converter. I got that changed out, as well as a tune up, and the issue went away.
  • ragellaragella Member Posts: 3
    Afternoon all! I have a 01 GP GT. The problem i'm having is that the fuel guage sticks(works when it wants to). I work for autozone, so I went ahead and picked up myself a new wiring harness (was told that the GM ones go bad) After waiting for the tank to be near empty, I dropped it. Boy was that a fun task. And, here is the best part - I start removing the old harness from the pump, and realize the pump, and the new harness aren't the same. So, I go back to work and do some homework - GM stuck a GTP fuel pump on my car. . . Any ideas as to why? :confuse:
  • rialto88rialto88 Member Posts: 2
    I have an 04 GP 66k miles. My wife drives this car mostly. She told me it had a slight miss. I drove the car and it does have a slight miss and the check engine light came on. I replaced the front spark plugs. I could not get to the back three. The repair shop said the pigtail on #5 injector needed to be replaced. The code I get is P0205. The replaced pigtail did not fix the problem. So now it could be one of a few things. Plug wire on #5 Fuel injector, or coil. Any suggestions? I know at this point the most expensive fix will be replacing the fuel injector.
  • hugmynutzhugmynutz Member Posts: 1
    Dude or Dudet,

    it's your mass air flow sensor. Trust me, i've repaired a million already. Easy test is to just unplug the mass air see if it runs fine, if so replace mass air.
  • lopez2362lopez2362 Member Posts: 1
    hey i am having same problem with my 2002 GP GT.just wondering if you have since fixed problem and what was problem hope to hear from you soon.anybody know how to fix this ??
  • billybillbillybill Member Posts: 2
    No luck yet with the problem......
  • ragellaragella Member Posts: 3
    No luck yet either on my end. After dropping the tank down the first time to swap out fuel pumps, and noticed I have the fuel pump for the GTP. Go figure, GM trying to save money by using overflow parts. I travel about 280 miles between fill ups. thats my guage.
  • Fast_Eddie18Fast_Eddie18 Member Posts: 2
    So Ragella you are still having the problem with your fuel gauge not reading correctly after replacing the, wiring harness for the fuel tank, fuel pump and sending unit assembly? I am reading the posts on the fuel gauge problem. I would have guessed the wiring harness would have fixed the problem?

    I have a 2000 Grandprix SE for my daughter.
    I am trying to trouble shoot the exact same problem with the fuel gauge reads full on engine startup and with a couple of minutes goes to empty with the low fuel light on! I even tried swapping out the tank fuel pump assembly with another good unit and still the same issue!
  • ragellaragella Member Posts: 3
    Fast Eddie.

    I gave up on the issue after the first time i dropped the tank down, to find out the fuel pumps are different. I work for Autozone, and I did some research. I have the same fuel pump, that goes with the GTP model. I picked up the unit for the GT. It was a pain in the royal, dropping the tank, to find this out. I use the odometer to keep an idea of how much fuel I have. I get roughly 280 miles on a tank. Let me know what you come up with.
  • Fast_Eddie18Fast_Eddie18 Member Posts: 2
    I just wanted to share this information with all the Grand Prix owners. To access the fuel pump assembly on a 2000 model year & (Other model years), you do not need to drop the tank. In the trunk behind the rear passenger seat there is an access cover for the fuel pump under the trunk carpeting.

    I stopped by my local dealership today and asked about other possible causes for the fuel gage reading incorrectly. The next step after replacing the fuel sender unit and still having the gauge read incorrectly is to trace the wiring up to the front car. Looking for burned spots or animal chew spots in the wiring. The service manager did say they have a special tool to flash the gauge cluster to test for functioning. Cost is $25.00 I would imagine there would be an additional labor charge too.
  • bigskidoggbigskidogg Member Posts: 8
  • brendadelbrendadel Member Posts: 1
    at times while driving my car when accelerating my car jerks before the gear is released and also I can be at a stop sign and my car turns off. It accelerates on its own and decelerates while driving and especially parked and when stopped at a stop sign and light to where it either turns off completely or feels like it will turn off. Could this be my fuel pump or crakshaft?? please help. thanks
  • kamlkaml Member Posts: 1
    i have a 1993 grand prix 3.1L and it's not getting power to the fuel pump relay when the rest of the relays(AC comp., primary & secondary cooling fans) are getting power. Is there a kill switch or a fuel pump resistor i need to know about?
  • gtp00gtp00 Member Posts: 1
    I HAVE A 2000 GRAND PRIX GTP WITH CODES P0203 AND P0303. I DO KNOW IF THE INJECTOR IS BAD OR THE WIRING HARNES IS BAD? I HAVE REPLACED ALL THE COILS AND THE IGNITION MODULE.
  • d588996pd588996p Member Posts: 5
    My fuel gauge is not working right. when I start the car it reads where it is, but when i drive it moves up and doesnt show me where it is until i start it again. it doesnt show if unless i keep turning it on to check. I thought it was the floater from the fuel pump but most floater issues have the needle stuck in one point not moving up and down, or moving up and returning down when stoppping. I dont want to replace the pump yet cause they are asking for 1000 Dollars. I think it might just be the gauge, other that the needle issue everything runs fine, no stalls no hard starts. turns on first try no problems,
  • d588996pd588996p Member Posts: 5
    did you ever find a solution the the gauge problem? I dont want to spend 1000 on a new tank if I dont need it.
  • erndog02erndog02 Member Posts: 1
    Hi I'm trying to help a bud replace his fuel filter on a 93 prand prix se. Here it be?
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