QuestionThis is a follow up. My 2006 Tucson v6 has 11,000 miles, the engine went light on, cart sputtered, died, and was towed to dealership.we were told "bad gas" (contaminated with water) the tank was cleaned, drained, etc. in the first visit. a few days after service, the engine light was on, and we returned to the dealer - there were misfire and catalytic converter codes. The tech said it was running fine, and cleared the codes to see if it was a sensor problem (no work on the vehicle). A few more days, engine light on again, sputtering car, we brought it back (3rd visit)and were told the catalytic converter failed. We replaced it. Then, a few days after that repair, the car has trouble accelerating, and we can't get gas in the tank regularly- it shuts off. Back at dealer for 4th time, we were told it seems fine (runs fine for them and no gas tank problem)although there were misfire codes. After insisting that someone else drive the vehicle, they recognized the sluggish engine and after 3 full days diagnosed failure of the 2nd catalytic converter ( I didn't know there were 2). question: is this a reasonable scenario for the result of contaminated fuel? Is it true that these problems could not be easily anticipated or avoided? And that there is no way to ensure that all damage caused from this incident is fixed (we have to just wait for things to fail?) Are there other explanations that could be explored?
AnswerIf you drove the vehicle while it was misfiring due to bad fuel, then this is indeed a reasonable scenario. Driving while there is a misfire causes unburned fuel to be dumped into the exhaust, which can ruin catalytic converters.
There's really not much that's a warning sign. You have no way of knowing you're getting bad gas. And the best sign that you may be damaging your catalytic converters is typically that the check engine lamp begins to flash, indicating a severe misfire. Once the converter damage is done, there will be no evidence of the damage unless there's a lack of power at high rpm (after the vehicle is otherwise running normally), or the check engine lamp illuminates with a trouble code indicating the converter efficiency is low. In fact, you actually have three converters on your Tucson-- one on each exhaust manifold, and another further back in the exhaust system.
I think you have a misconception that there are continued failures due to the bad fuel. Actually, the failures occurred prior to the initial repairs, but were likely undetectable at that time. Realistically, the dealer had little way to know that the converter was damaged without the check engine lamp illuminating. While simply clearing the codes is a step of dubious value, it would seem that the dealer did indeed follow a reasonable process. The only way to guarantee there is no converter problem-- because of their design on this vehicle, you cannot visually inspect them-- is to either until the vehicle displays symptoms, or to just replace them with new ones. No honest and competent repair facility would recommend replacing a catalytic converter unless they have some evidence it's bad. That would be asking you (or Hyundai, if covered under warranty) to pay for repairs that may not be necessary.
One possibility, and I have no way of knowing whether this is the case, is that there was no fuel issue in the first place. Your car could have been misfiring for some other reason. But if they replaced each manifold converter separately, and each time that temporarily made the car run better, this scenario is unlikely. If one of the manifold converters is blocked, this will make the engine misfire because the exhaust will be at least partially blocked on 1/2 the cylinders.
