Help! My check engine light is flashing when I fill up with gas!?

Question

I have a 2004 Hyundai Accent that is doing really weird things. A couple months ago, the check engine light started to flash every time I fill up with gas. The car shudders at idle, almost like it's going to stall, but when driving is fine. The engine light flashes while the car is moving, is off when the car is shuddering in idle, and comes on solid when the car is idle and not shuddering.
I've taken it to the dealership and to AutoZone for diagnostic work, but I can't seem to be told what the problem is and I don't want to do $700 dollars of work that the dealership "thinks" might fix the problem.
I commute an hour to work and an hour home, and this is making me pretty nervous. I'm a stickler for maintenance on my car, so there's nothing that I've missed as far as service. The car is ready for it's 45,000 service soon, and it will go in, but I want to get this problem fixed first, so the dealership doens't try to work one over on me.

Thanks!

Maybe I should expand.

First off, my car is still under warranty, so the dealership hasn't washed their hands of me.

Second, I am perfectly willing to fix anything wrong with my car, and ensure that all the preventative maintenance is done to have my car in tip top shape. The problem is that no one (the three different mechanics that have looked at my car) can figure out what exactly the problem is, and what I am not willing to do is simply try replacing everything to see if something works.

For those who provided good, solid answers, thank you. I'll be taking your suggestions to the dealership again this week.

Answer 1

The check engine light flashing indicates a condition in the engine where unburned fuel is entering the exhaust system it is flashing to let you know that there is a pretty good chance that the catalytic converter is being damaged and since this is an expensive and important to emmissions part it requires more protection. the most likely cause of this is a misfire on one or more cylinders. the shuddering and almost stalling also would lead me to think of this. I would ask around for the name of a competent independent garage. and have them diagnose it. they should be able to come up with a likely cause.

Answer 2

I have a Mini Cooper, and it happened that the light for the GAS CAP being closed was on the same circuit as the warning light for 'Check Engine' that could signal major repairs. It turned out that you're not "supposed" to turn on the car while the gas cap is open, or remove the key from the ignition while pumping gas or something like that. Stupid.

While this doesn't explain the car stalling at idle and the other problems you describe, you might just make sure that the gas cap is closing properly and don't do two things at once the next time you are filling the car with gas.

I'd make sure the car has ENOUGH ENGINE OIL, by checking the dipstick (which a friend can easily do if you don't know how), and waiting for the service to have them check the electricals and figure out the stalling. The Mini dealer wanted $108 to check my circuits outside the normal maintenance time, the crooks. But that's the way of the world these days.

Anybody believe as I do that computer-chips in most cars are WAY more trouble than they're worth? Idiots driving anywhere near civilization with Ion-beam headlights designed for driving on the moon please abstain from comments. We already know where you're coming from, and up your tailpipes is all I have to say.

Answer 3

If its the yellow check engine light than hopefully its something simple like bad fuel to air mixture. You can un-hook the battery for a couple of minutes and then hook it back up and hope it will reset the computer. You also might try a grade of gas above what you normally use, it will burn a little hotter in case there was to much water in your tank for your engine to run properly. If its the red check engine light, you should have a good mechanic look at it soon.

Answer 4

If you have a good dealership in your area, they will not be trying to get one over on you. That would be the small shop guys. Your engine light could be something as simple as your oil needs changing or your coolant is not working. Always get your engine checked when your check engine light comes on. As far as gas goes, as you using the grade the manufacturer recommends? Sounds like trouble with the Injections, or carburetor, whatever you have. Maybe something simple like the gas filter. You need to take care of it now, before it causes problems for your engine.

Answer 5

OK, wild guess, but look for the EGR Valve (exhaust gas recirculation). It's a round vacuum valve about 2 in. wide somewhere on the intake manifold, with a little hose in it. When it's COMPLETELY cold put two fingers into the valve and move it back until it's seated properly, the take off the vacuum hose and plug it. If it runs OK at idle, that'it. They're not too expensive, prolly less than $50.

Answer 6

Auto Zone doesn't do maintenance and the dealership probably washed its hands of you when your warranty ran out. You want it to get you back and forth to work but you dont want to pay the price to Ensure the car will. Just take it to a garage and pay whatever for the mental freedom of knowing it has a clean bill of health. Do you have a choice?

Answer 7

what it sounds like to me is the fuel filter. its maybe a five dollar part get the clear one its easy to see if it gets pluged. when the fuel filter is pluged it sputters and the check engine light will come on because its not getting enough gas. or it could be the gas pump in the tank its a fuel pump. it maybe not bringing up enough gas but you should do the filter first that will tell you whats causing it. my mom had the same problem before is how i know.

Answer 8

you have to shut off your car when you getting gas!!
because when tank cab is open inside pressure changes given car comp. mix messages and it gets crazy !
sound like you have small wiring problem on your car. but wiring problems needs a lot of time to figure it out.
when you go for diagnose tell them a open the tank cab when car is run then scan it!!!
good luck.

Answer 9

can't guarantee an anser. their computers should give them a reading that tells exactly what is wrong with the car , but one common issue is the gas cap is not tight.

i generally run some injector cleaner every few thousand miels... it reduces some of this stuff...

Answer 10

Try replacing your gas cap, make sure you get the correct one, it might be a venting problem. Few people i know we having a problem similar, and that was it.