2005 Kia amante, suddently ,like a fuse goes out the engine started running rough,at low speeds, raw gas smell, stop & go is horrible in town. On the interstate getting up to 70-80 is possible. White smoke of raw gas at low rpm yet eng temp is normal, radiator fluid is constant. I suspect an electronic failure given the immediate nature of the problem. could a ecm do this or other module. Is there a test for it ?advance auto said their tester showed everything fron 2 upstream oxy sensors failures to 3 cyls not firing properly. with limited funds any help would be appreciated

Run a compression test. Sounds like a bad head gasket, letting coolant into the cylinder and causing misfire. I think you will find one (or two adjacent) cylinders have much lower compression than the others. There should not be more than 20% difference from highest to lowest.

Put a can of a product called "Seafoam" in the gas tank. Also do the following procedure.

Here are some of the causes of surges, stalls at stops, slow idle speed, erratic idle speed, rough idle and engine hesitation (and other problems), it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.

i would check all the basics like spark plugs and check for vacuum leaks around the intake manifold.With a can of 2+2 carb cleaner while engine is running --if idle goes up or down that is were your leak is--
check egr too, Lee

they are mixing fuel these days but look for spotson dry pavement and touch with a cloth and smell to verify

try this procedure and let me know if it cures the problem.

Here is the common cause of surges, stalls at stops, slow idle speed, erratic idle speed, rough idle and engine hesitation (and other problems), it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.

Sounds like its either fuel or ignition. Have someone turn the car over while you sniff the exhaust.
If it smells of raw unburnt gas , fuel is not the issue , your problem is most likely ingition. Car might run rough at first when it does start , due to being slightly flooded.
If no gas smell probably a fuel problem. Possible low fuel pressure , or no fuel injection.

let your car idle go back to the tail pipe if it seems to be steaming alot , and or smells like antifreeze then you have a head gasket problem or a gasket leak alowing in directly into your engine

My personnel fix for this.

Here are some of the causes of surges, stalls at stops, slow idle speed, erratic idle speed, rough idle and engine hesitation (and other problems), it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.

Change speed sensor located near the gearbox.

This should show up easily on the ECU diagnostics computer at a mercedes dealership. Basically your fuel mixture is way too rich causing your car to be heavy on gas, have a raw gasoline smell, and not run right. Something like this can be caused by a defective oxygen sensor (but that usually produces a check engine light) or it might even be a defective ECU. There is really not way of knowing for sure until you do a proper diagnostics where they hook up your exhaust at the same time and do an emmission test. In most cases it's some sensor that needs replacing.