2001 Hundai Accent blinking CEL (P0304 Cylinder 4 misfire)

Hi Jack,

thanks for the response. So would you recommend replacing the injector? I've heard of having the injectors flushed. Is that a possible solution in this case, and if so, is there much cost savings in that route vs. Replacement? Or maybe that's only good for a clogged injector, and not a weak one?

Thanks again,

John

Here's the latest. I took the injectors out to replace the #4 injector, but the Auto Parts store didn't have any in stock, and would take a few days to get. So, I went ahead and swapped injectors #3 and #4. Started it up, and it exhibited same symptoms. Took and had the codes read, and got P0304 again. I asked them to reset the codes, so I could be sure this wasn't just left over from before. After the reset, even though the CEL would blink during idle, it would extinguish during normal driving. This continued until I got home, and later took it for another drive. After the CEL blinked during idle again, the CEL came on solid during normal driving, just as before. Had the code read again, and again got P0304. So, it would appear the injector is not the problem.

I tested the coil pack with everything disconnected per the hmaservice. Com site, and compared the readings to the specs. For the secondary coil resistance, between terminals 1&4 and 2&3, I read 14.5 kOhms vs. The 10.3-13.9 kOhms specified. For the primary coil resistance, between terminals 1 &4, I read an open vs. The 1 Ohm specified. I suppose this is indicative of a problem, but I am skeptical since I did temporarily replace the coil, but changed it back immediately after seeing the same symptoms at idle. The car was still missing at idle, and the CEL blinking. I did not drive the car at all with the new coil, so perhaps the ECM needed some time to reset?

Do you think this is the problem, or do you have some other suggestions?

I've been traveling, but had a chance to look at the car again last night. I began just by checking the compression just to completely rule out any mechancial issues. Everything there looked fine, but after I put everything back together, I cranked the car again to make sure it ran as before. It had become very dark by that time, and I noticed that as the car was idling, blue sparks were coming from around the body of the coil to the metal mounting frame. If I opened the throttle up, the sparks disappeared. This would be consistent with the car running rough at idle, and smoothly at higher speed. When I add everything up above, it seems to clearly point to a coil problem, but I'm skeptical since I had temporarily replaced the coil earlier, and noted no difference. As I mentioned, I did immediately remove the new coil after noticing no difference at idle, so perhaps it needed more time to run to correct the condition? Does this sound feasible to you?

I would without a doubt change the wires 1st, Pull the NO4 plug and inspect it for any abnormal conditions, if the wires dont cure the issue than its deffinately the coil. Good luck

Im sorry I missed the point that you already switched the wires. Had a rough night lol. I would go with checking or replacing the spark plug as stated above but from my experience with being a Hyundai technician it sounds like that coil is bad, try spraying some water on it while running and see what effect that has if the coil arcs more and the misfire gets worse I would really reconsidering putting the new coil back ito the vehicle

Hi, thanks for your response. I had already put in a new plug, to no effect. So, for my last test, I took and swapped the coil outputs to the #1 and #4 cylinders, ran it for a while, and then had the codes read again. My thinking was that whereas before I was consistently getting P0304, I should now see P0301 appear. Sure enough, this was the case, and in addition to the stored P0304, I now got a P0301, as well as a P0300 (random misfires), and a P0303. I attributed this to coil degradation, and will install a new coil. I hope my logic here was sound. I figured since the #1 and#4 cylinders fire together, all else should be equal. Does that make sense?

Thanks again,

John

Update: I installed the new coil, and again noticed no difference in symptoms. I noticed that the new coil also had small blue sparks coming from it at idle. Tried spraying water on it as suggested, and it made no difference in engine performance. I had the codes reset, but haven't had a chance to have them read again. I will let you know what I find out there.

I'm thinking of trying another set of plug wires, though I'm doubtful that's the problem. These were lifetime wires, but not a premium band (Xact or Exact, I believe). I think there must be something else going on. Whatever it is only seems to affect the idling, as it runs smooth at higher rpms and the CEL stops blinking. Any further ideas or suggestions appreciated!

Update: replaced plug wires, no difference. Read codes again, got p0304, and p0507 this time. Sprayed some starting fluid around the injectors, and noticed no change in idle for cyl. 1-3. Spray around #4 made a significant difference. My guess is that injector o-rings needs replacing, as cylinder 4 is sucking in too much air. Sound reasonable? Only thing bothering me about this is that when I swapped injectors 3 & 4 earlier, the car exhibited the same symptoms with the same P0304 code. As always, thoughts & ideas appreciated.

Yes, I believe you are exactly correct. Before I went to the trouble of new injector o-rings, I went out and tried to localize the intake leak more closely with the starter fluid first, then trying to plug the leak with a cloth and my hand. Definitely the leak was coming around the manifold gasket by cylinder 4, and when I plugged it as best I could, the check engine light stopped flashing. This also fits with the head work I mentioned earlier when the timing belt broke. This work was done about 6 months ago. My feeling is that the shop should reinstall the gasket for me, since this is not that long ago. How would most shops handle this?

Thanks again for all your help. I'm sure this time the real problem has been identified. I'll follow up with a confirmation after I've had the chance to have the repair made.

I have seen plenty of these intake gaskets go bad on hyundais, But you through me a curve ball with the arcing at the coil, seems to be multiple issues here.

I was finally in town long enough to take the car into the shop, and they did repair it for me free of charge. I did not have the opportunity to speak with them about what exactly was done as it was right at closing, and the mechanics had already left. After I got the car home, I looked under the hood and it appears to me that they repaired it by gobbing gasket sealer around the leaking area. I can't say for certain, but I'm fairly sure they did not install a new gasket.

The car seems to run okay, and the check engine light is off and stays off, so it seems okay for now. My concern is about the longevity of this repair. What's your opinion on this, and how the repair was handled?

Replace the ignition coil wire harness, you can get all 4 coil wire's for around $17-$25 on ebay.
The cover plate rubs the wire's causing them to lose fire. Easy fix. Not costly. Worked on my 2007 Hyundai accent & it was reading misfire on #4 cylinder