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Thread: Chevy Cavalier sputtering/ stalling on CNG

  1. Default Chevy Cavalier sputtering/ stalling on CNG

    My Chevy Cavalier used one full tank of CNG perfectly, with no problems. When the CNG was empty, it automatically switched over to gas, but the console light on the dash was slow to switch, and blinked a red light to check guages or something like that. I drove on gas alone for 1000 + miles. The next time I filled the tank with CNG, the car drove about a block and then died. I got it started long enough to get the car off to the side of the road. It wouldn't start for 20 minutes. It started again, and I drove it a few blocks to a safer location, then I turned the car off and looked under the hood. It seemed overly hot under the hood.. I restarted it but it required me constantly pushing on the gas pedal to keep the fuel flowing. I drove it 70 miles on the freeway. As soon as I got off the freeway, it immediately died and would not restart for 20 minutes. I got it started again and drove it directly to a Chevrolet dealer service center. They kept it for 1 full day, it never died on them, and they said there was nothing wrong with it. We disconnected the CNG system so I could drive it on just gas because I didn't trust the CNG system. Drove it another 1000 + miles on just gas. Reconnected the CNG system, and have the same problem. It sputters or dies because of lack of CNG fuel making it to the engine. I have to rev the gas pedal constantly to keep the cng flowing. Does anyone have any insight on this problem. The Chevrolet Dealer is obviously incompetent.
    Last edited by luvbeefcakes; 08-03-2008 at 01:58 PM.

  2. #2
    Join Date
    Dec 2007
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    Cadillac, Mi. / Deland, Fl.
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    Default Re: Chevy Cavalier sputtering/ stalling on CNG

    The "check gauges" red light is normal. When the fuel level gets low, it reminds you to look at the gauges (fuel gauge in this case) so you don't run out of fuel. In a gasoline car it means something, in a CNG it is just letting you know that it is going to switch in a few miles. Your first sentence says the car used "one full tank perfectly". Is this car new to you and you have only used one tank or has it been running normally on CNG until now? The fact that it won't start for 20 minutes or so might be something other then the CNG system. Normally if the car won't start on CNG after 8 seconds, it should switch to gasoline and start. Where did you fill with CNG? Same place you filled before and is it a commercial fueling station? If so, did they have any problems with other customers who filled the same day you did? Did you happen to notice if the car was actually running on CNG when you were having your problems (red light off)? Do you have any check engine lights? Did the dealer who had the car for a day retrieve any stored codes when he scanned (I hope) the ECU's? What year is your Cavalier? Maybe we can lead you down the right road to fix this problem .

  3. Default Re: Chevy Cavalier sputtering/ stalling on CNG

    I just bought the vehicle. It is a 2001. It was running on gas when I bought it. It ran on CNG with no problems the first tank I put in it. Later, when the car would not start on CNG it would not automatically switch over to gas. In fact it has never switched over to gas except the one time when the full tank of CNG ran out. I had to disconnect the mixer plug under the hood to disengage the CNG system in order to force it to run on gas.
    I did fill the car at a commercial fueling station when the problem started. I have not contacted them to see if others have had problems. The problem is definitely with the CNG system. It runs fine on gas. The problem must be some component of the CNG system that controls the flow or mixture of fuel when it is running on CNG. There may be an additional problem of it not automatically transfering to gas if the CNG is not working properly, or it may be the same problem with two different results (not starting/running and not transfering to gas). This is my first Cavalier, I'm a BMW girl, but BMW doesn't make CNG vehicles for the US *heavy sigh*. Can you help? Thanks.
    Last edited by luvbeefcakes; 08-04-2008 at 12:14 AM.

  4. #4

    Default Re: Chevy Cavalier sputtering/ stalling on CNG

    Check out this thread...the gas mass sensor could be your problem. http://cngchat.com/forum/showthread....ht=mass+sensor

  5. Default Re: Chevy Cavalier sputtering/ stalling on CNG

    Thank you. I believe I have figured out the problem. The car started just fine for me today. While it was running, I shook the electrical connection on the side of the gas mass sensor, and the car immediately died. The electrical connection must be loose or have some contamination on it. I'll have a look at it, and let you know the conclusion. Thanks again.

  6. Default Re: Chevy Cavalier sputtering/ stalling on CNG

    We disassembled the entire gas mass sensor. It looked sparkling clean and as fresh as the day it was born in there. Absolutely nothing abnormal, dirty, wet, or corroded inside of the GMS. Put it all back together, started the car, and let it sit and idle for about an hour. It never died. Drove it several miles, It never sputtered or died. The electrical connection on the side seemed tighter and more connected after we put it back together, so my guess is that the electrical connection was not fully connected before. Maybe somewhere in the 1,000 mile drive the electrical connection got loosened. The car is working just fine now. Thanks for the tip.

  7. #7
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    Default Re: Chevy Cavalier sputtering/ stalling on CNG

    Glad you found the problem . Long distance troubleshooting is, well troublesome. If you have a problem in the future and need to disable the CNG system, rather then pulling connectors apart, there is a fuse in the fuse box on the drivers side of the car marked "CNG". Just remove it and the car will start and run on gasoline.

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