2002 Hyundai Elantra idling rough

hyundai
elantra

#1

Dear Car Talk
My mother in law has a 2002 Hyundai Elantra that she bought new. It has just over 40,000 miles, mostly local driving with very few road miles. She has been sick and the car hasn’t been driven for several months until recently when she moved to my house and I drove the car here. At that time the service engine light came on and it is idling rough in drive and runs about 3500 rpms in park .A friend did an analysis and it showed a throttle position sensor problem.We replaced the sensor but that didn’t correct the problem. A second analysis didn’t show the sensor problem but showed misfires on two cylinders . My friend thinks the problem is a clogged fuel system and suggest that I drive the car for a while and use a fuel cleaning additive. Does this sound logical to you. I would hate to drive the car and ruin the engine.
Tommy


#2

Unless the throttle is open and making the engine idle at 3500 RPM, I would suspect the Idle Air Control valve is open too far, letting in too much air, and the computer is making the fuel system deliver too much fuel.

The car has low miles for its age and there could be some deposits in the injectors, but that wouldn’t cause this problem.


#3

I think you should make sure there’s enough oil in the engine, enough coolant in the system, enough air in the tires, and then fill the tank with fresh regular fuel, add the appropriate few ounces of something like Seafoam, an additive you can buy at a car parts store, and take a ride. Or several rides. The car needs to be run and it will be better. If it will go a few hundred miles in longer trips it will probably run better.


#4

shanonia

    June 1

Unless the throttle is open and making the engine idle at 3500 RPM, I would suspect the Idle Air Control valve is open too far, letting in too much air, and the computer is making the fuel system deliver too much fuel.

The car has low miles for its age and there could be some deposits in the injectors, but that wouldn’t cause this problem.


#5

If the car was not driven for months,I suggest draining the old fuel and adding fresh gasoline. Fuel stabilizer should have been use to prevent fuel from going stale and gumming out the fuel system.


#6

Fuel won’t get stale in a month. It takes more than 6 months, perhaps over a year.


#7

Several months is what the OP said.Could be more than 6 months,we don’t know.


#8

Bill

Just for informational purposes, I drove it to and from the dealer's service department and the problem seems to be fixed.  I am going to start driving it so old gas, if that was the problem, won't be a problem now.   As of this minute it has 41, 014 miles, roughly 2500 a year.    During the earlier years she was still active but even then most of her driving was less than 5 miles a trip.  I would be surprised if she were driving 100 miles a month over the last year or two.  She told me that her son took it for gas once a month.  She always gave him $15 and he came back with a full tank.

Tommy


#9

My opinion only, but I think asking people to scroll to read a post is rude.


#10

Do you think this fairly new user did this on purpose???

Cut them some slack, @VOLVO_V70
or perhaps offer some constructive advice on how to fix their post.


#11

I would suspect an Idle Air Valve problem or a vacuum leak; the latter caused by aged rubber or rodents gnawing through a vacuum line.


#12

If driving the car seems to help, good chance there’s some gunk in the fuel system or spark plug tips. Once the engine warms up, try to run the car at freeway speeds for 3-4 miles a couple of times a week.