Letters: Accent’s ‘racing’ engine concerns owner

• Reprints

Q: My 2011 Hyundai Accent is a driving and traffic hazard. The problem is that the engine will jump from an idling phase and begin revving up to a very high rpm. It happens intermittently.

I brought it to the dealer last month. They said they checked it out and found nothing wrong. They said to bring it back if it happens again.

I’m sure it will happen again and I believe something is wrong with the computer. I need some information to counter their reluctance to repair the problem. Please help. – Mike, Norridge

A: Looking at the service information for your Accent, it appears that the engine in your car still relies on an old-fashioned cable to link the accelerator pedal to the throttle valve on the engine. Most new cars rely on a gas pedal sensor and motorized throttle valve. So, your Accent controls the idle rpm with an idle speed control actuator. It’s installed on the throttle body and controls the intake air that is bypassed around the throttle plate to maintain proper engine rpm whenever the throttle is closed.

The actuator could be sticking or the powertrain control module, which controls the actuator, could be at fault. I suggest you contact Hyundai’s consumer affairs department to help you resolve this problem; visit hyundaiusa.com or call (800) 633-5151.

Q: The check engine light is coming on intermittently in my 2003 Pontiac Grand Prix (3800 V-6) with 64,000 miles. The scan tool shows code P0440. When I clear this code, it might go a couple of months before it reappears. I replaced the gas cap but the code returns. What other things should I be looking at? – Mike, Chicago

A: The gas cap was a good and fairly inexpensive guess. The P0440 code sets when the power control module detects a large vapor leak in the evaporative emission system. Possible sources of a vapor leak in this system include the gas tank, the charcoal canister, and the assortment of lines and hoses between the fuel tank, the charcoal canister and the engine.

When conditions are right for the PCM to test the EVAP system, the PCM commands the canister purge valve to open and the vent valve to close. This allows engine vacuum to enter the EVAP system. Then, after a specified amount of time, the PCM commands the purge valve closed, which should keep vacuum trapped in the EVAP system.

A fuel tank pressure sensor is monitored by the PCM to determine if the vacuum remains or decreases too rapidly (which indicates a leak). A smoke machine should be used to test the system for leaks. You could perform a visual inspection of these lines and hoses, but many times it’s difficult to locate a problem without the aid of a smoke machine.

Another possible issue is a partial blockage in the purge line. This could cause an intermittent condition. And, if the fuel pump recently has been replaced, I would suspect a problem with the o-ring on top of the tank where the fuel pump module is secured.

To find a competent repair shop for dealing with this issue, visit the Illinois Environmental Protection Agency’s website, epa.state.il.us/air/vim/reportcard.html. Then, click on “To find a repair shop using ZIP code.” Enter the appropriate information and look for repair facilities with lots of repairs and a letter grade of A or B.

Questions for Ira Siegel? Call the Auto Advisor Hotline at (708) 633-6839 or e-mail ira.siegel.is@gmail.com. Siegel is an automotive instructor and an automotive service excellence-certified master auto technician.