04 accent hissing noise? Help needed.
 

Hey guys, this is my first post I really need your help and input. My 04 hyundai accent about 2-3 months ago acquired a hissing noise which seems to be coming from the middle of the engine compartment. The car only has 100,000 miles on it.

It is a constant hiss that only stops when the gas pedal is pushed initially. I have looked all over the car and can not see any fluids leaking at all. It is pretty loud and can be heard easily outside the car when the car is on.

I hooked up my obd2 reader and found these codes:

P0304-Cylinder 4 misfire (I notice it when the car sits at idle for about a minute)

2x P0121- Throttle Position circuit range/performance problem

2x- Evaporative emission incorrect purge flow.


Any ideas?

bump! Really need some help.

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I suspect a vacuum leak. Has any work been done to it recently ?

0304 and you hear a hiss ???

That's tooo easy,, use a spray bottle with water, and spritz along the seam where intake manifold meets the cylinder head.. water hit vacuum leak,, it will make a sucking sound as water sucked in through the crack..

You can use a can of carb or WD-40, engine will change note when flammable get sucked in.

Evap code, disregard until vacuum leak/misfire remedied

TPS code,, maybe, see that occassionally

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Any updates ? I would not drive it with a misfire, but that's just me...

Well I installed a new tps and that hasn't helped at all. The car used to have a small misfire at a stop(like stoplight) but now it does it while driving every once in a while.

Gas mileage has definitely gone down as well. I've been meaning to do the water spray idea, but I have no garage and it's been raining for the last two weeks.

I've tried to get under the car and look around but without a car lift I cant get an angle that sounds like where the hiss is coming from.

I have an 2001 Accent and I would get a hiss when i pushed the gas pedal then it would go away. I was getting O2 and tps codes and check engine light was on for a month or 2. Also my fuel economy went down. One morning I was leaving for work at 430 in the morning and it was about 20 degrees outside and went to warm up the car and came back and found the exhaust leak in the flex pipe under the car very small. I bought a new one on ebay out of canada for $70. Put it on myself unplugged the battery and everything was as good as new again.

Alright, I don't see the leak, but since I have the same symptoms I am going to give it a try. What gaskets do I need/part numbers?

www.hmaservice.com
 

http://www.hmaservice.com/data/Passe...G/ecdd017a.gif

http://www.hmaservice.com/viewer/con...E%C2%A0Muffler > Repair+procedures&sitinfolist=12%5E1235%5E12350600 %5Enone%5E801%5E1%5EENG%5EHY%5ELC13%5E2003%5Een%5E 16%5Enone%5Enone%5Enone%5Eshop%5E%2412%5E1235%5E12 350600%5Enone%5E801%5E8%5EENG%5EHY%5ELC13%5E2003%5 Een%5E16%5Enone%5Enone%5Enone%5Eshop%5E%24

This is what I did. Before you do the work go to Hyundai buy the 2 gaskets for the front pipe and buy all new nuts for the front where it connects to the cataylitic converter and new nuts and bolts where it connects to the tailpipe. They will all be useless and rusted. I used a cut grinder or just split them off they were too rusty.

Oh almost forgot you will have to re-install the o2 sensor on the new pipe from the old one also.