This has happened countless times to me. But do not search forums, you will quickly be up in arms with expensive "coil solutions" and many other half applied logic. Change your knock sensor.

You can get one on eBay for 10-20$ Hyundai authentic. It is a 5-10 minute job and I would say could be done by any level of skill. All you do is disconnect one wire and unscrew the sensor (following connecting the new one and re-screwing).

LET ME STRESS THIS ... keep your old sensor. I have to basically do this twice a year and I have a lot of luck just cleaning up the old sensor as a backup that will at least prolong buying a new one for another 3 months. It has worked with two of my old sensors so far. It is cheap and quick to only do once or twice a year!

Your shaking, shutoff, electrical, and transmission WILL ALL BE FIXED. There are not multiple problems. Even though it seems like it is time to junk your Accent, try this before anything else and don't buy it for $100 at an auto store.

40,000 miles on my Hyundai Accent, 5 years old. I had been warned about the coil packs going bad. I thought I wouldn't have to deal with that problem for "some time to come". WRONG! It's now a year later and all four have gone bad at different times. I have replaced all of the coil packs as needed at the time. No sophisticated diagnostic equipment necessary; when the coil pack goes bad the car is running poorly and missing. Isolate which one by removing the wire from the coil plug one at a time. If there is no change in the car's idle when you pull the wire-then you've located the correct coil pack. I have now just started to have to replace the replacement coil packs! It appears that this is a COMMON PROBLEM and WELL KNOWN and RECOGNIZED. Apparently the replacements aren't any better than the original OEM parts?????? I hereby suggest that Hyundai do a recall and replace the defective coil packs! I have owned two other Hyundai's. Both were 2009 Elantras and sold those d/t other mechanical issues. I must admit that I am no longer considering another Hyundai !!

This car is an absolute LEMON! I purchased this car in 2012 and it has given me trouble ever since. The coils were always going bad, engine light kept coming on, and there was always something wrong with it. Now to top it all off, the timing went and now I have more costly repairs...have to pay for the repairs because I still owe on the car. I will never buy another Hyundai again and don't recommend that anyone else does either. Buyer beware of Hyundai vehicles, I don't care how good the deal seems.

This is the 4th time replacing the coils . I was told the last trip under warranty that all 4 got replaced but told today only two so now again I have to replace the coils on my dime . I also was told today That Hyundai new their coils weren't any good and the mechanic knew that if all didn't get replaced at once I would continuously have an issue . However they only replace the ones that have gone completely out under warranty . now that my warranty is out . I have to pay the money out of my own pocket . .I will never buy a hyundai again or shop at reliable imports in Springfield Mo .I bought a new car so I wouldn't have issues . This issue started a 30,000 miles .