2017 Elantra, intermittent cylinder 3 misfire p0330
 

Hi,


First time posting on this forum and have a bit of an ongoing story of my 2017 Elantra engine. Basic story is that I've been having a cylinder 3 misfire for over 2 months now that has not been properly repaired to this day. I am a mechanic and I am not attacking the mechanics at the dealer as I know intermittent issues can be tricky. There are a few issues I didn't like while dealing with them.


1. CEL came on, I hooked up my shops scan tool, found misfire on 3, did not clear the codes and booked it into the dealer for the next day. They phoned me later in the day, said they could not get a code to appear and said to come pick it up. I sent them a picture of what I found with my shop scanner and they decided that was good enough and did a coil/spark swap from cylinder 3 to 2, they drove it said no codes came up and if they did, bring it back and they would know if there was an issue. I left the dealer and code came back on within a block, brought it straight back. They scanned it and said same misfire on 3, I left it with them and they worked on it the next day, which ended up being an ecm update, courtesy of a technical service bulletin. I picked it up the next day, drove it home and no issues. Thr next morning on the way to work it started misfiring again and CEL came on. Back to the dealer.


2. They have my car and update me telling me that my spark plugs need changing, I need a fuel injection system cleaning and my air filter was plugged. I immediately phoned them and asked the service writer to go look at my air filter as I changed it a week prior myself. He came back and said it was brand new and the tech put it on the wrong work order (everything else matched up though?). I objected to both the spark plugs and system cleaning as the code would have switched from cylinder 3 to 2 if the spark plug was bad. This was not covered under warranty and I ended up doing it for the sheer fact to have it on file of them doing it. They did the spark plugs and injector service cleaning. The code came back as soon as I left the dealer. They told me that sometimes it takes a while for the system cleaner to get through and will run rough, I asked why they didn't drive my vehicle or warn me about it. Car goes back in.


3. Next day, service manager phones me and let's me know they found the issue, leaky injector! Right on, they found it, perfect, but no injector for a week and they have no loaner vehicles. They take a used injector from another car and put it on mine so I can drive it to work, a few days into driving it, it starts to misfire again and CEL comes on (this is very intermittent and the CEL comes on and goes off within seconds). I phone the service manager and tell him it's coming on with the used injector, he says that's odd and there's only a tiny chance that the used injectors also bad. He tells me I can still drive it, should be fine until the new injector comes in. I know it won't work with the new one but I'm not a Hyundai technician. I bring my car in a week later for the new injector, get it installed and am on my way. A few days later, same thing, misfire and CEL. Back to the dealer.


4. I was gone on a small vacation for a week left it there and told them I'd be gone until the following Friday. I got a message from the service advisor on the following Friday saying the technician drove my vehicle and it was good to pick up. I asked what they repaired and she said nothing, as there was no code and the issue couldn't be replicated. I told the service advisor that the service manager had told me they were going to rip it apart if they have to to figure it out and I didn't want it until it's fixed. So I had to wait until the following Monday to talk to the service manager. He had it there for another few days and finally got the code to come up and said they believe it's the intake manifold gasket. I waited a week, they got the part and installed it, I drove it until today and the CEL is back on.


Long story for people to read, but this is my experience so far with my Elantra. At this point I don't know what to do, I'm 5 hrs away from any other dealer and just want this repaired.

This is something that might be considered.
A scope needs to be hooked up to monitor at least 4 inputs and the freeze frame data and graphing need to be examined to determine which input is failing.
It sounds simple , but can require some effort to pin down. I'm pretty sure you realize this problem can be difficult to find.

Exact same issue with my 2017 Elantra
 

My 2017 Elantra has had the intermittent cylinder 3 misfire for about 3 years. It’s been to the dealer, and they replaced the plugs and the coil pack, but that did nothing to solve the issue. When the cylinder 3 misfire occurs, the check engine light comes on, and the engine vibrates. If I shut off the engine and restart the car, the misfire usually goes away for awhile.
I don’t believe it is an injector problem. When the cylinder is misfiring, there is no unspent fuel going to the exhaust because the catalytic converter does not get hot. My guess it is a computer problem where the injector is not getting a fire signal for some reason. It’s good to hear others have the same problem. Anyone know of a solution? Thanks

If the testing procedure suggested earlier is performed the cause will be found and a fix may be available depending on what was found..

Man I’m glad to know other people are having the same issue, I wish someone had some resolve. Might just go trade mine in while it’s not misfiring and there’s no light on.

There is a function on a scope that can record certain inputs at what time and a knowledgeable tech can find what is happening and when.
This is what may be required to determine just what is happening . If the place doesn't have the tech or equip to do this you may need to find a shop that can do this.

There are good Mobile techs out there that just may have that equip and find and correct the cause. They are so good other shops keep them very busy.
Ask around and you may find one that can get to the bottom of the problem.

I had a cylinder 3 miss fire on my 2020 Enaltra with just 9700 mile on it.. CEL was on, let it sit over the weekend.. Took to dealer that following Monday.. The service manager told me that there was no CEL on nor any history stored.. Now with just over 37km on the clock, never had it come on again...

Without having the vehicle to actually do some detailed checking , all I can ask you to do is;

See if you can note exactly what you and the vehicle are doing when the problem shows up.
Sometimes,if climbing a hill it shows up things like that.
The more info you can provide the better I may have a chance to offer a cause. Sometimes we have to play detective to close in on the problem, especially if we don't have the equip to do the detailed checking. Can you do this?

Same problem
 

Same issue with my 2017 Hyundai Elantra continuous misfire on cylinder 3 with engine light always on. Solution is to somehow fix the clips on the ignition coils that clip into the wires while your car is idling bad lift your hood and kind of jiggle each one of the clips you should be able to find which one is kind of loose if there's more than one when you find the one that's loose then you could do what I'm doing and rig it up and but just whatever it takes to make it stay until you get to the dealerships if you are having that trouble I'm a Lyft driver myself so the idling bad is not a good thing for me at all or passengers for that matter the main fix is to get the new updated shaft design that they have made for the ignition coil packs that's what you tell your Hyundai mechanic to do.

Low compression will cause a misfire
 

You need to have your mechanic preform a cylinder compression test as low compression will cause a misfire. You other people are over analyzing it. There is a class action lawsuit on Hyundai making bad engines for sometime. You need a cylinder compression test, is your gage readings around160-165 psi? Normal is 185 psi. 160-165 is considered low compression and that will cause a misfire. I have a 2014 Elantra same dealership story I did everything you did $2000 in repairs still stalling and code for.misfire. Bought a remanufactured crate engine and the problem disappeared. My car started stalling at 76,000 miles no warranty as I bought it used transmission failed at 103,000 miles had the dealership replaced it for $3,600 and that price included some of the “tune-up” bull****!!!! That didn’t fix my stalling and misfiring codes. They did 4 new injectors, 4 new coils @. 4 new spark plugs nope didn’t fix the problem

Low compression
 

https://cimg7.ibsrv.net/gimg/www.hyu...123e20a8a1.png

There are tools that can do what a flight recorder does and the vital signs of the engine are recorded as the vehicle is driven. The data can be reviewed and then see what is dropping out or changing and then go from there. Not too many places have that equip or knowledge of how to examine the inputs and spot when something is not as required. A good mobile mechanic might have that tool and the knowledge to obtain that info.
It is just like anything else, you have to find the right person/shop ti diagnose the problem. It can be done. The misfire is the result, but the root cause needs to be found and that can take a little time and effort.

i've had my used 2015 Hyundai Elantra for 18 months. For the first year straight the car drove seamlessly, over the last 5 months i've had misfiring issues. Changed oxygen sensor, catalytic converter and fuel pump so far nothing has fixed it. Have tie rod issues. The misfiring is on and off and the hyundai dealership where it was last repaired os saying to change the catalytic converter manifold after just changing the fuel pump a week ago. I'm so tired and frustrated and have not gotten it resolved. The car has been to the mechanic over 6 times

Time for a independent mechanic to do a compression check.

2017 Elantra SE cylinder 3 misfire Code P0303
 

I've had my Elantra since 2018 & with about 108,000 miles ( and runs like new) As best I can recollect this intermittent error code has started to occur within the last year. It has gotten more frequent in the last month and so I did research this code number and it seems as though except for a random plug issue it's not the coil pack although just today I flip-flopped cylinder 3 with cylinder 4 just to rule it out. I took it out for a spin and everything seemed okay but that's not really telling me anything as far as I'm concerned. I'll cut to the chase: in my investigation I ran across a very good independent mechanic from Canada who has a very sophisticated diagnostic scan tool that has oscilloscope capabilities and what he found out is that the error is coming from the ECM. He actually proved it and was able to show where the signal when it's supposed to go to ground is only reaching ground for approximately 120 microseconds and then it jumps back up to two and a half volts so the ECM for that cylinder instead of it being a square wave is virtually at two and a half volts all the time. According to him a resistor in the ECM is failing and not allowing the system to go to ground and flagging the misfire error code. I haven't called Hyundai but plan to do so next week. I'm guessing this part with installation and programming is going to run about $2,500.