2009 Pontiac G5 drops RPM and won't accelerate on highway when low on gas

I took my car in to a GM dealer and they replaced the fuel tank due to a leak. The cost was under covered under a special recall via GM. Now when the car is low on gas … (Say about 50-60 miles left on a tank, or lesss) and I’m on the highway the car will not accelerate. When I try to speed up the RPM’s drop and it seems like the engine isn’t getting gas? almost like i’m running out of gas. I can still drive on residential streets going up to 40-45 mph but when i get on the highway it won’t continuously drops and won’t let me get up to speed.

Brought it back in , they replaced the fuel sensor… but that still is not fixing the problem.

Below is link to a video of what it does.

Notice the RPM dropping…the whole time im trying to accelerate and pressing down on the gas pedal

Take it back to the dealer, or a different dealer.

I would quickly recognize when to get fuel to avoid the problem if it was mine. Maybe if you consider the tank will be empty at the 1/4 mark life would be good. Of course, if there’s some worthwhile satisfaction in demanding that the gauge and miles to empty indicator be totally accurate then continue with taking the time to force GM to get it right. How much are you willing to spend in time and money to have the gauge working to a 1 mile till empty accuracy?

Personally I wouldn’t care if a fuel gauge didn’t work at all. I don’t trust any of them. I fill up based on mileage.

I agree Rod Knox, but we are selling the car to a close family friend and I don’t want to give it to him with this issue. If i were keeping the car myself, I would have never put this much effort into all this.

Selling a vehicle to a close family friend is a fantastic way to reduce the number of close family friends.

It’s a real pain and it’s unlikely that any dealership mechanic will do it but just bending the swing arm on the tank sensor to raise the float 1 inch will significantly shift the gauge reading toward empty.

And when operating with the fuel level so low that the engine loses power the fuel pump is overheating and it will fail due to overheating sooner or later.

Are we to understand that the car operates as it should with a tank 1/2 full. If so most of the low fuel lights we have had light up before we reach the 50 miles left to empty warning. I refuel our vehicles just as soon as they get below 1/2 mark.

Yes, car runs normal until I get to about 50 miles left or so … Which is usually just before the gas light comes on.

Problem solved

Agreed, but it wasn’t doing this before we took it in to the dealership, so they screwed something up. And again hate to sell it with lingering issue. Just frustrating.

It is likely that when the tank was repaired the sensor float arm was bent downward somewhat and skewed the gauge reading. I am not aware of any manufacturer giving a specification for setting the swing arm but the situation @mytjo is having is one I have struggled with a few times and found it safest to always move the float to be pessimistic. And I once dealt with a car that had 2 fuel level sensors wired in series in a stepped tank that would drive a man to drink. Lucky for me I already did.

Just curious - how many gallons does it take to fill it when it gets to the point when the problems occur?

The next time you have this problem, open the gas cap in a quiet location and listen for a whoosh of air being sucked into the tank as you’re opening the cap. If you hear this, see if the problem is fixed after putting the cap back on. If so, come back and tell us.

Have everyone pretend 100 miles to empty is 0 miles to empty. Is that so hard? Why you depend on computers so heavily and defy an easy common sense solution is not the world I grew up in, everything is not always perfect and I think I am on workaround 3 million or so. 50 miles till empty, I fill up when I get to half a tank. Putting that much faith in the system is beyond my comprehension, so how many hairs above e on the gauge is 50 miles till empty?

Maybe my cars do the same thing but I’d never know because I never get below 1/2 tank. Agree though that’s a good way to burn the pump up.

This thread reminds me of the moron a few months ago that was upset because he would run out of fuel when his onboard readout said he could still go 13 miles.

I think everyone is lecturing the wrong person here. Why not tell them to just put tape over the gas gauge.

I think the dealer should fix this on their dime. They are the one’s who replaced the tank on a recall. The way they have it installed, anyone going by the gauge is in reality running on fumes.
And as pointed out, that is not good for the pump.

I really don’t think that the owners should always be relying on the odometer…that’s what the gas gauge was put there for.
Plus, they should not have to worry if they borrow their car to a friend, and having to explain the backwards way of figuring out when you’re about to run out of gas.
Then there is the problem of being on a trip, and it’s 40 miles to the next station and you only have 5 miles worth of gas.

The mechanic didn’t do anything wrong, it’s just one of those unforeseen problems.
Even if the dealer would redo the tank for an hour’s labor, I’d be happy.

It wouldn’t take that much to drop the tank and pull the pump assembly out and bend the float arm a little.

If it read empty and you still had 1/4 tank, that would be different, I wouldn’t do a thing.


My guess is that the fuel pump is either struggling due to an obstruction created during the pump change or failing, possibly due to an inability to breath in, possibly created by an EVAP system obstruction created when the tank was changed.

The pump obstruction and/or weakness guess is because the pump appears to be using “head pressure”, which is the pressure created on the pickup tube by the weight of the gas itself, to assist it. Ergo, when the gas gets low, the “head pressure” drops below the pump’s need and the pump has trouble feeding sufficient fuel to the motor. The best way to test for this is to test the pump pressure at the motor’s feed line when the vehicle is exhibiting the symptoms.

The second guess is because if the EVAP system is malfunctioning and the tank cannot breath in as the fuel is pumped out, it creates a vacuum in the air space that opposes the pump’s efforts and make pumping the fuel difficult. The pump is trying to pump against a vacuum. The check this, remove the gas cap when the vehicle is exhibiting the symptoms and allow the tank to breath in. If the symptoms disappear, suspect a vacuum buildup.

Post back with the results. We do care.

PostScript: I hadn’t seen Rod’s post when I wrote this. I’ll leave my suggestions, as they are still valid, but Rod’s theory bears serious looking into as well.

@Barkydog - what the hell does depending on computers have anything to do with this? Thats like saying you have to look out the window to judge how fast your going. Hell all cars now are big computers.

Some of these comments are incredible. Someone needs help not chastising.