DR. Gizmo Part IV

January 3, 2010

"Dr. Gizmo"

By Phil Arendt

Mechanical Problem Raises Engine Idle Speed

Question 1
My 2002 Hyundai Santa Fe with a 6-cylinder engine has a high idle and the check engine light is on.  I took the vehicle to my local mechanic who replaced the throttle position part.  The car ran better after the repair, but the engine still idles too fast and the check engine light turned back on.

I returned to the repair shop, but the mechanic cant find the trouble.  He did some tests that tell him the engine idle is too high but he does not know the cause.  He says that the trouble might be in the computer, but he doesnt want to replace it unless he knows for sure that it is the problem.  He says that the only trouble code in the computer is a high idle code and everything else is fine. 

Whats wrong?  B.R., email

Answer 1

Something out of the ordinary is causing this condition and needs attention. The code that tells your mechanic that the idle is too high is a clue he should contemplate.  He knows all the sensors are functioning correctly because there are no malfunction trouble codes indicating a circuit or sensor has a fault.  Since this is the case, ask him to consider a fault that is mechanical instead of electrical.  He may find that the gas pedal or one of the throttle cables is binding.  Maybe a throttle cable is not properly secured.  Maybe there is a problem with a cruise control cable. Once he looks into a possible mechanical fault, he likely will find the cause of this condition and make a lasting repair.

Symptom Points Toward Fuel Pump   

Question 2

Recently, I purchased a used 2002 Saturn Vue with 26,000 miles.  It looks and drives like new.  However, every once in a while I hear a buzzing sound in the rear.  I hear the sound every day as I drive to and from work.  My office is 18 miles away and I hear the buzzing sound once or twice during the drive.  The private party that sold the vehicle to me told me about the sound before I purchased it.  He said he did not know what causes the noise.

I took the vehicle to my local mechanic.  He drove it several times during the course of a day and to and from his home.  The buzzing noise never surfaced.  He said it is possible that the fuel pump is making the sound, but he will not replace it until he actually hears the noise.

I am concerned the fuel pump is making the sound.  I am worried it will fail and strand me on the road.  What do you think is causing the buzzing sound? L.T., email.

Answer 2

I understand your concern.  No one wants to be stranded on the side of the road.  A failed fuel pump could certainly stall your vehicle.  Be this as it may intermittent noises are difficult to diagnose.  Without hearing the sound, your technician can only guess as to what might be causing the noise.  Despite this, there is hope.

Your vehicle has two fuel pumps a primary and secondary pump.  A check of factory technical service bulletins found one bulletin that might shed some light on the cause of the sound.  Factory bulletin number 03-06-01-007 refers to a noise similar to your description.  It states that the secondary fuel pump fuel pressure regulator associated with the secondary fuel pump might cause a buzzing sound.

Ask your technician to look up the bulletin in his technical library.  If he has the proper equipment, he can perform tests in his shop that cycle the fuel pump.  If it makes noise during tests, he can verify the condition.  If the fuel pressure regulator buzzes, he has pinpointed the source of the noise.  If indeed the pressure regulator is the source of the buzzing, according to the technical service bulletin replacing the secondary fuel pump module will end your concerns.

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