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Discussion Starter #1
OK, so I started having a rough idle and my 2012 Elantra would throw a code, but only once in a while. It was the P0304, cylinder #4 misfire. So after getting that and clearing it several times over the span of a month or so (it would only occur intermittently, about once every 2 weeks or so), I swapped out the coils for cylinder 1 and 4. About a week later, VIOLA! I get a CEL that reads P0301! So it went to cylinder #1 with the suspect coil. I order a new coil, put it in and go have some rum whilst patting myself upon the back.

No such luck, sadly. In a few days I get another P0301, with the new coil in the #1 position. I clear it and get it again and again, far more rapidly now. I also am constantly getting and additional code, a P0261 (cyl 1 low voltage). I am not certain that I did not also get that before as I was concentrating upon the P030X. I then tried swapping coil #1 and #2. The code stays on Cyl #1!

Any ideas? When I swapped the coils the first time (#1 and #4), the code followed implying that the coil was bad. I then replaced it with a new coil, and I get an error again. Unlucky with a bad coil? Should I try replacing the injector (looks pretty easy). The code has stayed on cyl #1 implying that it may NOT be the coil. I am slowly going nuts here, please advise! Thanks.
 

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OK, so I started having a rough idle and my 2012 Elantra would throw a code, but only once in a while. It was the P0304, cylinder #4 misfire. So after getting that and clearing it several times over the span of a month or so (it would only occur intermittently, about once every 2 weeks or so), I swapped out the coils for cylinder 1 and 4. About a week later, VIOLA! I get a CEL that reads P0301! So it went to cylinder #1 with the suspect coil. I order a new coil, put it in and go have some rum whilst patting myself upon the back.

No such luck, sadly. In a few days I get another P0301, with the new coil in the #1 position. I clear it and get it again and again, far more rapidly now. I also am constantly getting and additional code, a P0261 (cyl 1 low voltage). I am not certain that I did not also get that before as I was concentrating upon the P030X. I then tried swapping coil #1 and #2. The code stays on Cyl #1!

Any ideas? When I swapped the coils the first time (#1 and #4), the code followed implying that the coil was bad. I then replaced it with a new coil, and I get an error again. Unlucky with a bad coil? Should I try replacing the injector (looks pretty easy). The code has stayed on cyl #1 implying that it may NOT be the coil. I am slowly going nuts here, please advise! Thanks.
The P0261 is an injector circuit code. If you want to do anything swap it with another cylinder like you did your coil and see if it follows.
 

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Discussion Starter #3
OK, on Wednesday my refurbished fuel injector showed up from Amazon. It was $32.68. I swapped it out in 15 minutes. But really it was a 10 minute job, very simple.

The car has run amazingly smooth ever since. I think that I can claim success thanks to you geniuses here on this forum. Perhaps I should wait a few weeks, but it has been smooth as glass since the swap.

One question. My car has had an intermittent rough idle for years now. Since the swap it is perfect. I am therefore assuming that the injector was the cause. But if that is so, why did I never get a CEL for a misfire or injector low voltage until just in the last 2 months or so? I could have cured this a few years back, had it thrown a code.....

Thanks forum folks!
 

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OK, on Wednesday my refurbished fuel injector showed up from Amazon. It was $32.68. I swapped it out in 15 minutes. But really it was a 10 minute job, very simple.

The car has run amazingly smooth ever since. I think that I can claim success thanks to you geniuses here on this forum. Perhaps I should wait a few weeks, but it has been smooth as glass since the swap.

One question. My car has had an intermittent rough idle for years now. Since the swap it is perfect. I am therefore assuming that the injector was the cause. But if that is so, why did I never get a CEL for a misfire or injector low voltage until just in the last 2 months or so? I could have cured this a few years back, had it thrown a code.....

Thanks forum folks!
The injector may have had a bad spray pattern and not atomizing well or just having a problem lifting the pintle correctly.

you can have some of these middle of the road problems with fuel that will cause an idle problem without setting a code.
 

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Discussion Starter #5
That is kind of what I figured. That sucks but oh well. Makes diagnosis a small nightmare. But, for now, all is like new!
 

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That is kind of what I figured. That sucks but oh well. Makes diagnosis a small nightmare. But, for now, all is like new!
It's kind of like when the throttle body get coked up and will cause idle, stumble and stall issues without setting any codes. When we see these symptoms in the shop the first thing is to put a vacuum gauge on and see if the exhaust is restricted or valves not seating good. If the vacuum is good we then clean the throttle body and if that doesn't cure it we will pull the fuel rail with the injectors and check the spray patterns. Over half the time we'll find one of more injectors with bad patterns or dripping fuel. Replace bad injector(s) and bam....runs great again.
 

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Discussion Starter #7
Great info! I assume you hook up the rail to a pressurized source of gasoline or some fluid to simulate it and have something hooked up to each injector's connector that turns each on and off and you just visually check the spray pattern?
 

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Great info! I assume you hook up the rail to a pressurized source of gasoline or some fluid to simulate it and have something hooked up to each injector's connector that turns each on and off and you just visually check the spray pattern?
Some systems can be done while under the hood. using a clear polymer 'catch can'. We plug in each injector one at a time. We use a strobe that's triggered by the injector circuit which gives a very good single picture of the spray pattern. Should be a nice even conical pattern. Other's we take the injector out to a simple flow bench where they can be tested with a pressure regulated fuel source and observe the pattern and look for any dripping.
 
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