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Discussion Starter · #1 ·
Okay iv done everything. I own a 03 hyuandai elantra. A month am half back my car started misfiring bad. So I changed wires. An plugs out. No help. So I changed all the fuel injectors out. That fixed up til a few days ago. Its back to misfiring again. Why do the injectors keep going out? Everytime it musfires my check engine light blinks the. It will stop an the light just stays still. Dont understand.
 

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P0303 misfire detect ?

Intake manifold gasket between intake and cylinder head is about every other day for cracking..

Engine running at idle, spritz along the seam with some carb, see if engine change character.. water spray bottle in stream and hear the water "jet" into intake as loud sucking sound as water drawn in via the cracked gasket into the intake stream..
 

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Discussion Starter · #4 ·
What would I look for to tell if that intake manifold gasket is leaking? Can that make your fuel injectors go bad. There brand new a month an half old. It fixed the problem for a little over a month. An not sure if this has anything to do with the misfiring. But after my fuel injecto promblems first started when I run the ac my permorance of the engine weakness. Before it was fine now i cant have the ac on or it takes for ever to get up in speed. it started when the car first started misfiring and after it was fixed for a lil over a month it wad still doing it. Not sure what that is or why.
 

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there are different kinds of engine misfires. there are rich misfires where there is too much fuel and there are lean misfires where there is not enough fuel. when the check eng light blinks thats a rich misfire. I always look for three things first; air, fuel and spark. sounds like either a problem with the air system or spark. have you confirmed that the coil pack is within spec, are the plugs gapped correctly, mass air flow working correctly, intake air temp sensor reading. is it hard to start in the morning? is anything unplugged? thats a big one I've kicked myself for forgetting to plug something back in after doing a service. are the spark plug wires going to the correct cylinder.


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Dealer tec with over 7,000 posts tells you he sees intake gaskets failing every week and you want to ignore him; strange.

I have also replaced the $8 intake gaskets on two Elantra's that owned because of misfire issues.

Fuel injectors almost never fail; have put 400k kilometres on a jeep with original injectors still working fine.
 

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Discussion Starter · #7 ·
No nothing is unplugged. An its start right up. But the way it starts is not like a regular start. It feels diffrent when it starts. An how did I ignore the man. I asked the an how i would tell if it is that.
 

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I guess you really didn't ; feeling cranky after 36 hours of night shifts.

Start with existing code maybe and go from there. Normally if intake is off and injectors changed new intake gasket would have been installed anyway.

Approx. one hour labor to replace gasket, some fasteners awkward to get to. Coolant hoses to intake usually removed.
 

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Discussion Starter · #9 ·
Its fine. But no the injectors are eletrical. So the intake gasket never got changed. Can you tell me if its a hard repair to do yourself. I have a little knowledge on working on cars. Not much but if I take something apart. Im usally good at remembering how it goes. If not I can take pics. But you opinion could I change the intake manifold gasket myself? Would I need impact? I noticed my air filter bow wasn't all the way pushed in to the hole by the battery. Didnt think much of itm but I was telling a buddy an he said that thing has to be all the way in or tge mass aur flow sensor will mess it up. Im hoping thats it but my luck it wont be. Any more suggestions or comments would greatly be appreciated.
 

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Yes mass airflow is sensitive, it measures air flow so ECM computer can match how much fuel to put in ; even a spit in the plastic intake can cause major idle problems.

If you have a code reader , the best starting point is always checking for them.

Intake gasket change is not that bad; only small 10 and 12 mm bolts , no impact needed.
It takes more patience than skill, there are posts on site showing pictures etc.
 

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Discussion Starter · #11 ·
Okay I was just trying to find a promblem lol. But I took out the air filter to see if car would drive any better. No it did not. I put it back on. But I went to auto zone to Get my codes read came up cylinder 2 misfire an oxygen sensor slow response. I asked if taking out the air filter would cause the oxygen sensor code. He said no. He also said the missfire can be causing the oxygen sensor to throw a code an if I fix the misfire the oxgen sensor might go away. Tell me thiss' if the intake manifold gasket was bad. Wouldnt all cylinders be misfiring? And what could make just one cylinder misfire? Also I was told by a buddy that if I spray dw40 all around the area of the intake manifold that if there is a leak the intake would suck it in an the engine would rev up because the dw40 is flammable? Is that true and could that damage yout motor?
 

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Refer back to post #2..

30 second inspection procedure time at most with engine running and spritz, and it been couple day now.

Elantra is common to crack intake gasket.. result is single cylinder misfire, maybe 2 if it crack between 2 adjoin cylinder, but most common is crack/broken gasket at #3..

Repair the leak, clear code(s) AFTER repair, see what happen..

Cant rely on ox values when what coming out of the cylinder is garbage, just goofs the ox values..

Do you have the actual codes the fella recovered, and not a generalized ox sensor slow response.. the actual DTC in P0xxx format tells us what the exact circuit is that the PCM see to be at fault.. there be 2 ox sensor, pick 1 for slow response, though I likely believe it to be B1S1,, that is why we need to know the EXACT P0xxx code
 

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Discussion Starter · #13 ·
No dont know the exact codes but I will get the. Tomorrow. Thank you I will be sure to focus on the intake gasket
 

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Discussion Starter · #14 ·
Alright didnt get the codes read today. My mind was else where but I sprayed dw40 around the gasket area an no rev in the motor or nothing. But I took my spark plugs out and 3 of them look used but cylinder 2 where its misfiring looked wore out bad. So I swapped the plugs around and it ran a tiny bit better. In my opinion. It might of ran the same an my mind waa tricking me lol. The plug was like a goldish brownish. The plugs are only 2 months old. What would make a plug go bad that quick? Also could my fuel filter play apart in this? I know if its a fuel filter promblem is read random misfire not just one, right? By the way this fuel filter has over 200k miles on it. Never been changed because its a in tank an you have to buy a new pump witch is 200 so I never changed the filter but always wanted to. This car has got a oil change every 3 thousands miles. Nothing on this car has ever giving me a promblem. So thats why thinking its not a major problem. I love this car for the fact nothing has ever went wrong with it till a few months back.
 

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Fuel filter wont give single cyl misfire.. all 4 injector feed off same rail.. only 1 main fuel rail with 4 "leaks"..

Only use NGK Platinum plugs.. see nothing but running issues when customers show up with cheap plugs or "gimmick" plugs..

Use only Hyundai wire set.. look at plastic ends of cable to plug for dis-color or burn spots or what look like freakish black lines/cracks/remnants of lightning strikes.. 2.0 wire ends good for this when they get aged.. do the actual wires maybe have a white/siver-grey haze about them ?
 

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Discussion Starter · #16 ·
No the wires so not they look the same as they did 2 months ago when I bought them. Okay if its not the wires,plugs,injectors,maf senor,intake manifold gasket, fuel pump n filter. What else could be causing it to have a single cylinder misfire. Im trying to do as much diagnostics at home as I can because im really broke at the moment. Aln also when its in park it dont seem to have a noticeable misfire but as soon as I put it in drive or reverse you can tell.
 
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