By December 13, 2006 0 Comments Read More →

Hyundai Runs Bad and Dies At Stops

I have a Hyundai Sonata. It recently started idling low, and has progressively gotten worse, to the point of stalling out when I put the car in reverse. Last week, the check engine light came on, and upon being diagnosed, it stated that I needed a new O2 sensor. This weekend, we changed that sensor, the spark plugs, the spark plug wires, and the air filter.

By Monday, my car was running even worse. Now, the engine is getting virtually no power (like the gas isnt getting into the engine), the car wont go above 20 MPH, and it is stalling out continually. So Monday, we replaced the battery. No change. Yesterday, we replaced the fuel pump, the fuel filter, cleaned the engine and changed a couple of hoses. It is still not running. If you can give me any advice as to what this problem might be, I would be very greatful. Thank you in advance.

Yo Holly,

First advice ..STOP SPENDING MONEY GUESSING! Spend $75 and get a proper diagnosis!!!! The idle problem could be something as simple as a vacuum leak in one of the vacuum hoses on the main inlet hose going from the air cleaner to the engine. Since you said you can t get the vehicle to go more than 20MPH, I would suspect you either have lack of fuel problem like a bad fuel pump (but you already replaced that) OR a restriction in the exhaust system like a stopped up catalytic converter. I m assuming the transmission is NOT slipping, but that the engine does not have the power to make the vehicle go any faster than 20MPH .correct?

Just so you know. If the transmission was slipping the engine RPM s would be high and the engine would be revving loudly but the vehicle would not be moving.

Since you mentioned the O2 sensor was causing the trouble code, it is highly likely that the engine has been running so poorly lately that the exhaust system is full of carbon (unburned fuel) causing a restriction in the muffler or catalytic converter. If the exhaust can not be removed from the engine via the tailpipe, the engine can not breathe in new air and fuel. It s just like you trying to run a marathon with your hand over your mouth.

To test the exhaust system, mash down on the gas pedal a few times as someone holds a rag over the tailpipe. (Caution this will be VERY HOT gases coming out, so wear a glove). With each mash of the gas pedal you should feel a large amount of exhaust gas coming out the tailpipe. If you don t, I would visit your local muffler shop and have them test your exhaust back pressure.

Austin Davis

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Austin Davis, consumer car repair advocate. "Hi there! I love to help people solve their car repair problems and I hope my site was helpful to you today. Thank you for stopping by."