My sonata with 2.4L engine, auto tranny guzzles fuel outrageously. I noticed when i start it in the morning, the engine shakes like its flooded with fuel until the temp guage reaches the half way mark. this also applies to starting the car all other times. i also noticed the car accelerates on its own when warm. Could it be a bad coolant temparature switch responsible for the longer time it takes to warm up?

Note: thermostat still intact.

Plz gurus help me out. thanks y'all

I once used ur model of car. Good car and runs smoothly.

However, make sure the cooling fans are not connected directly on ignition start. There is a temp gauge sensor by the right side of the engine, make sure the wires are connected correctly.

Cheers.

Sounds like CTS, o2 or MAF/MAP issue. Both needs to be tested to know which is faulty. But if you cant troubleshoot manually, i would suggest you scan the car.

When you said the car accelerates on its own when warm, how exactly do you mean? The idle speed increases without your input or it stays as high as 1k or 2k rpm at idle and remain there when engine is warm or it keeps going up till it reaches the red zone? Does the car have IAC? How dirty or clean is the throttle body?

Ikenna

Probably your TPS (Throttle Position Sensor) is faulty. That's why it moves by itself without accelerating. Have it scanned to know the exact problem.

Thanks guys, i did a scan twice, no code stored, check light is off. I removed the harness for the TPS and drove it, gear wasnt selecting properly, had to plug it back. when warm, Rpm stays at 1k when its on drive and ac on, once the Ac thermostat switches off the Ac, it goes above 1k, and when on neutral, it goes to 1.5k. Have changed 3 CTS from last week, still same. car doesnt idle well till the car is warm(noticed it runs great when the temp guage reaches the halh way make). Before it gets warm, high fuel consumption, bucking, no stalling though.

Irwindickson: Thanks guys, i did a scan twice, no code stored, check light is off. I removed the harness for the TPS and drove it, gear wasnt selecting properly, had to plug it back. when warm, Rpm stays at 1k when its on drive and ac on, once the Ac thermostat switches off the Ac, it goes above 1k, and when on neutral, it goes to 1.5k. Have changed 3 CTS from last week, still same. car doesnt idle well till the car is warm(noticed it runs great when the temp guage reaches the halh way make). Before it gets warm, high fuel consumption, bucking, no stalling though.

I wouldnt have bothered with TPS, if i were you. TPS has nothing to do with the symptoms your car is having. I wouldnt test my TPS if my car was rough idling. I would check my TPS if my car acceleration becomes very poor. Unplugging TPS connector would make the idle speed go high, but not rough idling, at least for Peugeots anyway.

I dont know about your car ignition system, but 1k rpm is way too high for me, not to think of 1.5k rpm.

You still havent answered us if the car has IAC. If yes, when was the last time you cleaned it, including the throttle body? Did anyone tampered with the throttle butterfly factory adjustment? I would check these out to figure out the high idle speed.

MAF? What system does your car have? AFM, MAF or MAP? Trust me, when MAF fail sometimes, you wont get the check engine light on the cluster. Troubleshooting MAF can a headache, unless you have the special tool or know the special method of testing MAF, especially the Bosch MAF. Its adviceable to have a spare MAF. It comes handy when troubleshooting a rough idling issue, even when you dont get check engine light. You simply swap in the spare, clear codes and restart the car. If improvement is observed after some minutes of engine running, then you have found your culprit. Or you carry out MAF test, if you know the method of testing the one or brand in your car or if you have the tool (like PP2000 for Peugeots).

Vacuum leak. A tiny leak on vacuum line would make an engine idle badly, but would idle normal when engine warms, depending the spot of the leak. Tiny leak tends to seal off when engine gets high (hoses will become softer and close up some small or tiny holes or leaks), but will expose the leaks or holes again when the engine becomes cold again. Such leaks can be very difficult to detect, since its not permanent. But there is nothing carb cleaner cant do in this regard, as long as engine is still cold.

Try the above. Goodluck.

Ikenna

Thanks man, will check it out

Fixed, had to change the TPS, coolant sensor, all injectors, fuel pump and air filter, and its now ok. thanks y'all

You killed the rat with an anti-tank weapon (all THOSE had to be changed?!!), but at least the rat is dead. Congrats and welcome to problem free motoring.

I had to cuz all these dia guess work was too much.

Irwindickson: I had to cuz all these dia guess work was too much.

Your old injectors, did you you at any point allow the mechanics clean ( so called "service" ) those injectors with carb cleaner?

Ikenna

Yea, i think that was part of the guess work, after they did, car ran alot better. Bucking came back before getting home from the mech.

Irwindickson: Yea, i think that was part of the guess work, after they did, car ran alot better. Bucking came back before getting home from the mech.

Cleaning the injectors with Carb Cleaner will damage the O-rings, which after awhile will start passing air into the intake manifold from the injectors and give such symptoms the car had. I wouldn't know if that was the cause of the problems you have fixed, but next time, don't allow anyone spray Car cleaner on the injectors with O-rings on them.

Ikenna

Cyberknight: You killed the rat with an anti-tank weapon (all THOSE had to be changed?!!), but at least the rat is dead. Congrats and welcome to problem free motoring.