Diagnosing Possible Misfires – Veloster turbo
It seems that a common issue with the Veloster turbo are misfires. These misfires can be caused by a large number of reason but here I will try to address the most common problems, how to diagnose them, and how to fix them. Chances are if your VT is having a misfire issue you will notice it. You hit the gas pedal waiting for that turbo rush and all the sudden the car hiccups, stutters, and jerks. This is a saddening event.
Disclaimer: I am not a mechanic, I do have many years of DIY experience with cars but am far from a professional. If you blow up your engine by misdiagnosing and incorrectly installing a part, that will lie with you.
I will do my best to update this post with new information, techniques, and maybe links to DIYs for some items as they become available. If you see anything in this that is either incorrect or misleading please PM me and I will make sure to correct it.
Symptoms
As stated above, if you feel sudden stuttering from the engine your car is more than likely misfiring. It is usually an obvious jerking (not to be confused with “the wave” that is commonly seen during partial throttle and is more attributed to the stock intake design and stock tune). You will also see your Check Engine Light blinking as the misfire is occurring.
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Possible Problems
The misfire can be caused by a number of different reasons, so let’s go through the list of common issues that have caused misfires and determine what exactly is happening in your case.
1)
Fuel delivery. This is a design flaw with the low-pressure part of our fuel line that attaches to the high-pressure fuel pump under the hood. There has been a recall issued by Hyundai for certain VT’s, full details on this and a way to see if your car is affected by the recall may be found in this thread;
VT Fuel Line Service Bulletin.
a. Diagnosing. To find out if this is your issue you will need two things. An OBDII reader and some kind of logging software. The preferred reader is the OBDLink MX/LX, preferred software is Torque Pro for iPhone or Android, and either OBD Auto Doctor or Dash for Windows. Once you have these set up you will need to monitor your fuel pressure. If your fuel pressure is steady at 2200 psi then you are probably OK here. If it begins dipping below 2000 psi and steadily declines even though RPMs are going up then you will want to replace your fuel line.
b.
The Fix. To fix the fuel pressure problem you will need to replace your fuel line. Even if your car is not listed by Hyundai as a recalled vehicle, you still may need to fix it. There are various vendors that have created a replacement fuel lines that is leaps and bounds better than what is offered by Hyundai. A DIY tutorial may be found here;
VT Fuel Line Replacement - Google Docs
2) Spark Plugs. Another common issue is a faulty spark plug. Usually a ceramic insulator has broken, moved, or been damaged in some way. An incorrect gap or broken electrode are also common issues that can arise. Finding a completely fouled spark plug is much less common but like the other issues is easy to diagnose and fix.
a. Diagnosing. To find if this is your issue you will need to pull out your spark plugs. You will want to try and make sure you know which cylinder each plug came from. Make a visual inspection of each plug by making sure the ceramic insulators are in good condition, checking the gap of each plug is at 0.028” and that all electrodes are intact, and seeing if all four plugs appear to have a similar “wear” or “patina” to them. If one or more plugs is completely black and covered in gas or oil you may have a fouled out plug. Take pictures and post them if you need confirmation on the possibility of a bad spark plug.
b. The Fix. If one or more of your plugs appears to have broken then that is probably your culprit, it would be best to replace all of your spark plugs at this time. Buy new plugs, gap them to 0.028” and place them in the car. Hopefully your car has returned to normal.
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3) Spark Plug Coils. The coils that Hyundai has used for our cars seem to have a short lifespan. It is not uncommon to find that one or more of your coils has gone out after 50,000 miles or so. To find out for sure can be a multi-part process.
a. Diagnosing. You will again need an OBDII reader and appropriate app. If a coil is the issue you should either seeing a flashing Check Engine Light (while the misfire is occurring) or your CEL light is on. You will want to connect your OBDII reader and find out what code is being shown. A P030X in which “X” is the cylinder in which the misfire is occurring. (Cylinder 1 is located on the left side of the engine when looking at it from the front of the car, or the closest one to the oil filler cap.) The best thing to do is move the suspected coil to a new cylinder, clear the codes, and try to replicate the misfire. If you again get the misfire, pull the code. If you do indeed have a bad coil, the CEL code should change to match the new cylinder you moved the coil to.
b. The Fix. To fix the issue simply replace the bad coil. Replacing just the faulty coil should be just fine, no need to replace them all unless you feel the need. Although if you have multiple coils that are faulty then replacing all of them at one time may be the best course of action. To source OEM coils either search one of the Hyundai OEM parts distributors or SoCal Garage Works, a supporting vendor.
4) Dirty Valves. As our cars get older and thanks to the nature of GDi engines your valves will get dirty. There are things you can do to slow down the effects of this like a good oil catch can set-up, using high grade fuels, a quality air filter, and going by the factory recommended schedule of using Techron to clean things out.
As the valves begin to get dirty they may no longer seat correctly, thus hampering air intake and exhaust flow and can create misfires. Diagnosing this issue is a little trickier as nothing may appear “wrong” but upon very close inspection by a trained eye things aren’t lining up. (Please note: this is a much more involved process, if you feel at all uncomfortable, it is recommended to have an experienced mechanic perform this diagnosis and repair.)
a.
Diagnosing. To begin you will need a borescope
(similar to this). Pull out the ignition coils and spark plugs and guide the scope into the cylinder. (Alternatively you can try to remove the cold pipe and go through the throttle body, or remove the intake manifold.) You will no doubt see that there is carbon build-up. The main thing is seeing if the valves are seating correctly. If you see gaps between the valve and head then there is major build-up and will need to be cleaned.
b. This Fix. Professional media blasting has been the most common over the years. This involves removing the head and blasting the valves with a “media” (usually walnut shells) to clean off the built up carbon deposits. This is a job for a professional mechanic.
As this common GDI problem becomes more mainstream and more cars out there are using direct injection there are now more options arriving on the market. Chemical products that do not require removal of main engine components have begun to emerge and become more popular but with mixed results. Although they may be somewhat effective these chemicals have not yet reached the level of walnut blasting. They could however slow carbon buildup when used on a regular basis such as during oil changes or every other oil change.
Conclusion
I hope this has been helpful, and as always if you have questions ask them. I am by no means and expert but I and many others on this board will do our best to help you with finding the source of your issues and getting them resolved. Not all misfires are caused by the above issues but the vast majority are. If your car is stock, or lightly modded and it still falls under warranty, then you may want to the dealership first. Some of these things can be costly and incorrectly diagnosing and “fixing” the issue can cause more problems. If you do not feel comfortable with this type of work then please consult a professional mechanic.
