2004 Hyundai XG350 • 185,000 miles

A month ago the car started dieing out of nowhere & would restart automatically. Then the car would die & after a waiting period it would restart. Now the car will start, idle for a few seconds & die and after hours it will restart. We checked the fuel pump & replace it, still no change. At times it will backfire. Sometimes when you start the car & touch the gas it will rev up but the second you let off the gas it dies. Other times you can start it & the minute you touch the gas it dies, Any help would be greatly appreciated!
October 5, 2011.

The first thing I would suggest is going to an Advance Auto or Auto Zone and they will usually run a trouble code check for free. You might have to go to a repair facility to get this done. But, It should not cost much.
There are a lot of possibilities. It does sound like a fuel system management problem. The fuel pump relay could be failing internitantly.
With the mileage on your car, there is a good possiblity that there is something that is dirty enough to effect fuel delivery. The injectors may be clogged or the Idle Air Control Valve, IACV, or emissions equipment such as the Exhaust Gas Return, EGR.
All you can do in these cases is take apart the intake up to and including the throttle body and the aforementioned parts, (which are located on the intake mainifold near the throttle boddy), and clean them.
Another possibility is the the catalytic converter is clogged.

Here is a link that walks through all general possiblities to diagnose the problem that is making your car stall.

I hope this information helps. Get back to us with the trouble codes if you need any help with that.

We have been told the fuel pump relay. However we are unable to locate it. Where is it exactly?

Oct 5, 2011.
The fuel pump relay is on the right side of the instrument panel in the center support under the radio.

I hope this information helps.

Hello, the problem description that ataylor72010 gave in the initial post is exactly the same as what happened to my 2004 xg350 with 120,000 miles. It has now been sitting at the dealership for over a month and they have not been able to fix it. Is there anyway to confirm with ataylor72010 that fixing the fuel pump relay remedied this issue? Thanks

Oct 28, 2012.
I sent a message to ataylor and he will get a notice of this post as well. So, hopefully he will respond and let us know if the fuel pump relay fixed the problem.

Problem solved---in my case it turned out to be a bad crankshaft position sensor. The car did finally throw that code in the end, P0335. It also had the ignition failure sensor code P0320. Ignition failure sensor was replaced first but the problem remained. When the crankshaft position sensor was replaced, problem went away. Car has been driven about 500 miles since then, with no sign of problem returning. Hope this helps somebody else.

Nov 8, 2012.
That is fantastic. I am always so glad to hear things turned out well and got fixed. Good diagnosis on your part. The information will help someone as I now have a little more as I always gain some everday that I work here. I learn information from customers all the time once the problem gets fixed. Diagnosis is hard enough in person. It is amazing that we get it done via texting each other.
So, I thanks you for letting me know how and what it was in the end so I can have that information to pass along in the future.
Information is golden as we say around here and I appreciate it.
Thanks much and take care.

Dr. C