Hey guys. I have owned my 2004 Cavalier since Jan of 2008 and things have been going pretty well till about now.

A few months ago I did a full tune up on the car which included:

Spark plugs, fuel filter, o2 sensor, coolant, stat, oil & filter, etc.

The car was running at its best after completing that work.

Well i just started noticing that the car felt like it has a slight misfire or bucking feeling the lower my gas became in my tank. It becomes really bad AS SOON as my needle is pointing at a quarter of a tank of gas left. If I was to give my car enough gas to get going (merging onto a highway as an example) it cannot get out on its own way which isn't safe. The thing misfires like crazy and feels like its running out of gas however never stalls.

However oddly enough as soon as I fill the tank bank up to full, its like the problem just vanishes completely until the gas starts being used up. For now I have been keeping the car over a 1/2 tank of gas just so I don't run into any issue's hopefully... I can still notice a slight misfire from time to time. The car just doesn't seem like it has the spunk like it used too anymore.

This issue has me completely stumped because I have never seen something like this before in my life. I did a full tune up like 2 months ago and it was running fine till about now. Also the problem seems to go completely away as soon as I fill up the tank? I could see if it was a sensor problem if it was doing it all the time. But it only seems to get worse as the gas gets lower in the tank.

Could this be a sign of a weak or failing fuel pump? My car just turned over 100K not too long ago. That really is the only thing I could think of.

One thing I have noticed the last few week is when I fill up my gas tank, it does something funky with the gas pump. Pretty much if I try to pump the gas out of the pump at full speed, it shuts the pump off almost like my tank is full? It will keep doing this unless i hold back the handle a little bit. Its almost like the gas tank is full of gas or pressure preventing me from filling the tank up at full speed?

Any suggestions guys? I do not get any check engine lights either.


2000 Buick Regal GSE - "Gods Grocery Getter is powered by an L67 3800" - 333WHP
12.900 @ 109.91mph 2.166 60Ft (Fastest 1/4)
13.374 @ 110.01mph 2.467 60Ft (Fastest Trap)

2004 Chevy Cavalier - 15.7 @ 90mph (Semi-Modded)

So no one has had this issue before in there car?


2000 Buick Regal GSE - "Gods Grocery Getter is powered by an L67 3800" - 333WHP
12.900 @ 109.91mph 2.166 60Ft (Fastest 1/4)
13.374 @ 110.01mph 2.467 60Ft (Fastest Trap)

2004 Chevy Cavalier - 15.7 @ 90mph (Semi-Modded)

i have a misfireing problem as well except mine does it when it first starts up after sitting in the garage all night and when i gun it. I have yet to figure out the problem.


-00Cav-

Sounds like some of the issues my wife's Cav had....


Yes, your gut is right. The fuel pumps were never great from 03-05 (just be glad you don't have an 03), so they don't tend to last very long.


Our 03's FP barely made it to 50k. My 04's is still going...lucky for me, I guess.


The FP tends to die without any notice, though little signs like that tend to be your warning..


It's a pricey fix, so be prepared.

Mine lasted till 98k miles, and never had any misfires leading up to it dying.
Mine is an 03...


My wife's 2003 Ecotec 2.2 liter Sunfire:
* 2 1/4 inch in and dual 2 inch out muffler Trans Am muffler
* 2 1/4 piping to a very long 2 1/4 inch resonator
* 2 1/4 inch catalytic converter
* an AEM true cold air intake NOPI edition
* 8 gauge ground wire kit
* Toyz front strut brace
* Russell stainless steel brake lines all around.

Mike85220 wrote:Mine lasted till 98k miles, and never had any misfires leading up to it dying.
Mine is an 03...

Lucky, I guess.


My wife does a bunch of city driving....

Your fuel pump is failing


- 2004 Cavalier - 124k, owned since new

Thanks for the replies guys. I been reading up on this issue and it looks like the 2003's had ALOT of issue's with the fuel pumps going bad as early as 50,000 miles!

Being I am around 100K sounds like a weak/failing fuel pump is my issue.

It seems that most of the replacement fuel pumps come with the complete sending unit so most likely will just get a whole new AC Delco kit

Unless someone suggestions another company besides AC Delco to go with?


2000 Buick Regal GSE - "Gods Grocery Getter is powered by an L67 3800" - 333WHP
12.900 @ 109.91mph 2.166 60Ft (Fastest 1/4)
13.374 @ 110.01mph 2.467 60Ft (Fastest Trap)

2004 Chevy Cavalier - 15.7 @ 90mph (Semi-Modded)