Hyundai Repair: 1999 accent engine light on, air flow sensor, intake hoses

Question
hi i just bought a 1999 accent engine light is on and sometimes the car is hard to start,it also bogs down when you go to take off.you can also feel what seems to be a bight of hesitation even when driving at normal speeds.i was told the codes that were coming up were 300,141,301,304,302,118,102.it has the 1.5 12 valve engine.i have changed the fuel filter,air filter,plugs,and wires,and put in a bottle of injector cleaner,also thought the air intake hoses might have a hole so i taped them up.while doing all this i had the battery disconnected to clear the codes,when the car is first started the light was out then came right back on.also tonight looking at it i noticed that the engine was cold but when the car was started the fan came on right away.any idea what to do next?

Answer
Ordinarily, I'd have you reread the trouble codes, but one of the trouble codes indicates your car may be overheating.  If you can reread the codes with the vehicle in its present location, do so.  If not, make sure the car is not overheating prior to taking it to have the codes reread.

The reason rereading the codes is important is that you may have already fixed some of the problems.  Because you have so many codes, it'll be difficult to keep track of what's been fixed without going through this process.  If *all* of the exact same codes come up in the *same order,* I suspect they may not have been cleared.  I don't recall which exact vehicles they were, but there were some Hyundais in the mid- to late nineties that wouldn't clear the codes by disconnecting the battery.  If that's the case, use the code reader to clear them when you have them checked, and then check to see if the lamp comes back on again.

P0102 indicates your air flow sensor reading is lower than expected.  This could be caused by running the vehicle with the air flow sensor unplugged, a defective air flow sensor, or a leaking air intake bellows.  If your bellows is leaking, it's possible that taping it may not be sufficient to fix the leak.  In most cases, the engine movement when driving the vehicle will pull the bellows open again.  

P0118 indicates that you've received a coolant temperature reading of 284F or higher from the coolant temperature sensor.  This could be because the vehicle is overheating, or because the wiring to the sensor is shorted.  It's also possible that the sensor itself could be shorted, but I've never seen this occur nor heard of it occurring.

P0141 indicates a perceived fault in the heater circuit of the rear oxygen sensor.  This could be caused by an exhaust leak, a faulty rear oxygen sensor, or by damaged wiring to the sensor.

P0300, P0301, P0302, and P0304 all indicate misfires.  The last two digits of the misfire code indicate the misfiring cylinder, with P0300 being a random or multiple misfire.  The fact that you have misfires on so many cylinders suggests that you may have a problem that's affecting the whole engine and not any particular cylinder.  This could be a faulty crank sensor (doubtful), poor fuel pressure, or simply running poorly because the engine is overheating.  If your engine is running poorly, you may need to investigate the cause of that issue to find the cause of the misfire.