Hyundai Repair: 2000 Sonata sputters after sitting at long traffic lights, 2000, Hyundai

Question
Hi Randall,

I have a 2000 Hyundai Sonata with 2.4L, manual.  The car runs pretty good however after sitting at a long light the car will start to sputter and when I try to accelerate it has no power.  I can nurse it up thru first and 2nd gear and it will finally grab somewhere in 2nd or 3rd gear and accelerate with full power.  This can happen any time I idle for a while.  It seems that it mostly occurs once the car has reached its running temp.  There seems to be a correlation between how full the tank is,  when the fuel is below 1/2 a tank it seems to happen more frequently but it really can happen any time it idles to long.  You usually can hear it coming, the engine will rev on its own or start to sputter but that isn't always the case.  The check engine light had been on for years but I unhooked the battery in January to get it to pass E-check and it hasn't come back on since.

I'm lean towards some sort of issue with the EGR system but before I start throwing money at it I wondered if you had heard of anything like this or had any ideas.

Thanks for your help

Mike T.


Answer
I believe that it has something to do with your fuel pump. If you notcie a difference as the gasoline reaches the half way point, you may be losing pressure, ro more commonly, the fuel pump may be overheating. Another sign of this is that it only does it as the car reaches full temperature. The reason the amount of gas will effect an overheat is due to the fact that on a full tank, the fuel pump is being cooled by the gasoline in the tank. As the gasoline depletes, the temperature of the pump rises and begins to act up more. Since it especially does it at an idle, it is another good sign of overheating, as when you are driving, more cool gasoline is flowing through the pump helping to cool it down again.

I would have run an engine diagnostics test on the vehicle when the check engine light was on to see which signal code had tripped that negative reaction. Now that the light has gone away, you may not be able to do that because your ECU (Engine Control Unit) has accepted this new way of driving.

There is going to be no positive way of saying, but since you think there is a correlation between the reaction and the amount of fuel you have, I would say it has to do with your fuel system.

The EGR is always a possibility, for if it is not functioning properly, at an idle, your vehicle will not have the intake mix that it is programmed to handle. Without the NOx flowing from your exhaust, it could throw your sensors off majorly.

I would call your local Hyundai dealer to see if they have had any issues with the EGR or fuel pump. Be sure to talk to them about past experiences they have had and describe what is happening to your vehicle in detail as you have here.

I hope that everything works out for you and that you are able to pinpoint the exact problem. If there is anything that I can answer for you, just let me know and I will do my best for you.