Here goes, I have a ’02 Hyundai accent 1.6L w/ 190,000 miles. Around Christmas one cold morning right after getting gas at a grimey service station my car started running like crap misfiring badly. Kicking and bucking it barely got me to work (6 miles). I took the car to an Advanced auto and had them plug it in to check the engine light. It was throwing multiple codes P0300 (Multiple Misfire Detected), P0301 (Cylinder 1 Misfire Detected), P0303 (Cylinder 3 Misfire Detected). I told the guy at advanced that I thought it was bad gas and he agreed, so I put some dry gas and Lucas oil gas treatment in it.
The problem seemed to get better within 50 miles, only misfiring when I drove it hard. I drove the car to NYC from Buffalo and back about 500 miles each way, each fill-up putting the dry gas and Lucas treatment in it along with premium gas. No problems the entire way.
The problem has come back and this time the gas treatments are not working. I am getting the same two codes along with a new code P0133, (HO2S-11 (Bank 1 Sensor 1) Slow Response) and the same symptoms, and to top it off my flex pipe has rusted out (for the second time).
So now I don’t think the initial problem was water in the gas, and I am not sure what to make of it. The problem seems to happen more noticeably when I push the engine (first gear, and when accelerating) but then seems to get better when maintaining a constant speed. Also, the misfiring happens all the time but more noticeably when the engine gets to running temperature. First gear is by far the worst when the engine is warm.
The car got a tune (filter(s), plugs wires) up about 6mo ago
The timing belt is old about 90k on it
A new crank shaft position sensor a year ago
New O2 sensor (the 2nd one past flex pipe) 6mo ago
Burning about ½ to 1qt of oil (synthetic) every 3k miles but no smoke
The car has the original clutch w/ 191k on it!
This is where I stand. I don’t care about the flex pipe or the timing belt. Unless I can defiantly pinpoint the problem to one of those two, the car has so many miles on it, to start dumping that kind of money into it doesn’t make sense. I have put a spark test light on each of the plugs BUT the problem does not happen when the car is idle so…it showed me nothing but properly functioning plugs. I was thinking the ignition coil (its original) but I think that would throw a code. Let me know what you think or where to start any advice would be helpful.
I love my car and I am very proud of it but I don’t have the money to be a hero