Misfiring/Hesitation issues.

Umm where do you get gas.... I would try somewhere else.... If you've fouled out an O2 sensor and are having misfires it's possible that you're getting low quality gas... Also make sure you are buying the proper grade of gasoline... A dealer should have the computer that will read all major codes that have ever posted since an ECU flash, however if it's a small dealer they may only have one of the crappy little hand held OBDs that you can borrow from any parts place, and most of those can't read pending codes... Additionally many will charge a diagnostic fee to use the nice computer.... Speaking of which does anyone know what software they use... I have a OBD tool that connects to my laptop PC but has fairly basic software and allows only the basic scan read reset features of a handheld.... Anyone know where I can get software to read ABS, and make/model specific codes... But see if it's the gas... If it isn't I'd check plugs and wires... Could be a wire popper loose or fouled plugs(considering the O2 went out already). Valve cover gasket could be leaking into the plug wells ect... These are just the easiest things to check and are by no means the only possibilities. If your light stays on take it in and get it read.

if you are having a ing misfife problem have the coil pac checked.theese are known to be faulity from the factory,as our mechanic stated above you could have a bad plug wire causing the missfire,but a scan would not tell you this,only ing missfire,sugestion,at night crank it and see if you see what we call a lightining show,you will be able to see if plug wires are bad rev enging a little if bad you will see the wires throughing biue streaks.

if you're still having the problem. just today i again took my '07 to the dealer. had already had the timing chain tensioner replaced due to some noise at startup and rough idle. ultimately they said there was an updated needed specifically to rectify this. would have thought of it, but it's running silky smooth now, shifting better, some power is back. dont know if it's just for an '07model,etc. but it's a possibility i suppose. good luck.

made a typo. it was an update made to the computer. also, i had thought it was gas quality the whole time.

The light doesn't have to be on to scan it, the codes should remain in history. Once you get the diagnosis codes that should tell you the problem, if it's misfiring it should also tell you which cylinder is missing. You can also check your wires by spraying them lightly with water, You should be able to see them spark out if they are bad. Also the sonatas had more then just 1 o2 sensor, possible they replaced the wrong one? You have 1 or 2 before the converter and 1 after the converter.

Having the same problem with my 2007 Sonata Limited. Took it to the mechanic, had the O2 sensor and spark plugs replaced. Everything was fine for a couple days, then boom, it started acting up again. Frustrating bringing it back to the mechanic as I work 40 miles from home. I also don't expect the dealership to be any less annoying with fixing the problem. This is quite annoying. I love the car, but I don't know hwo much longer I can deal with this. Have you got any answers on your end?

I have been dealing with the same situation for about a year now and I can take it anymore. The car hesitates after driving in a while. I have changed all the spark plugs, fuel filter all the knock sensor and I just changed the intake manifold gaskets car ran alot longer before hesitation started. Still have same problem, my next step in the 02 sensor. If you have not had the intake manifold gaskets replaced you may try that a leaky intake manifold gasket can cause the same problems.

I have an '07 Sonata with almost 50K and so far (knock on wood) no issues at all, love it. I would suggest trying a different dealer? The check engine computer does store histories until cleared, them telling you otherwise makes me suspect their level of interest.

this has been such a helpful blog. I am having the same hesitation issue on my '07 sonata Limited (just not running like it used to). Its at 46k. they just did a tranny flush and no change. Looks like noone has really found the "golden solution" to fix. Anyone have a suggestion as to where I should start?

actually now that i read it more carefully, looks like the only "fix" that worked was jamesg, who had a good experience after they replaced the timing chain tensioner and did the software update. Maybe I will start there. Thanks all for letting me know it's not in my head! (that's how the dealer treated me)

I have the same problem with my 2007 Sonata SE. Dealer did the software update on the computer, but on the ride home, the check engine light came on with the rough idling. The dealer is unable to tell me what is wrong with the car, but suggested I replace my spark plugs and coils. Of course the car has 65K on it so it is not under warranty. I went the Consumer Affairs route and Hyundai denied the claim to replace the coils and plugs. I had the dealer replace the plugs... the car is still running rough, but better. The check engine light is not on yet. The dealer tested the coils and said they were all fine and to hold off on replacing them. Does anyone have a better answer to whats wrong with the car?

the misfire and the O2 sensor trouble lights point to an intake manifold vacuum leak. have you had any of the air intake duct off recently, or installed an aftermarket intake?

all of these issues can be directly related to a bad O2 sensor. if the O2 sensor before the cat is bad or fouled it will make the car run terrible and misfire. in order to trip a check engine light from a bad O2 sensor it must reach a certain point. they dont just come on if they arent 100% perfect. next time the check engine light comes on i suggest going to someplace like autozone to see if the O2 sensor is bad. they will tell you for free. if thats the case its a simple fix and its cheap if you know how to use wrench.

I the check engine light is blinking, that means there is a severe engine misfire which would not be caused by an intake vacuum leak or an o2 sensor. Granted if your car is misfiring it can damage the o2 sensor because too much unburned fuel is going into the exhaust. You need to pull the spark plugs and take a look at them. See if any of them are wet, black or smell like fuel. That is a good indication that the cylinder is not firing correctly.

I changed an air filter, but no other parts of the air duct system were touched. The car isn't throwing codes for the O2 sensor only p0300 and the occasional P030. The spark plugs were replaced 3 days ago... so far it seems better, but not perfect. If too much gas was being released into the cylinder, that could explain why my MPG seemed to go down a little.

P030 is an O2 sensor code.

Are you using a paper air filter or an oiled one like a k&n?

Hmm... Interesting. If P030 is an O2 sensor code, then I take it P0300 and P0301 are related to the O2 sensor somehow?

P0300 is multiple cylinder misfire. Vacuum leak or bad/dirty maf sensor are the likely cause

I am currently using a paper air filter.

Buy a new car, did you say your car was a 1956? this is a classic by now.

I have a 2000 Sonata and its reading number 5 cylinder misfire. is this from the coil?

Hi my 2007 Hyundai sonata is doing a code p2187 engine running lean at idle and will do the codes you all are having now but the problem is intake manifold gasket take carb cleaner spray around it while car is running it will idle up when it picks up the carb cleaner and you may even be able to hear the hissing sound it makes gasket 13 dollars and it can be a bit of a pain to put in.

I just had the same issue with my 2008 Sonata 2.4 and had it serviced by Hyundai. They replaced the Intake Oil Flow Control Valve (24355- 2G000). It is a $70-90 part and it cost me $300 to get it replaced by Hyundai. Good news...it fixed the problem for me! As mentioned above, there are many possible causes of rough idle. I just wanted to share because I hadn't see this mentioned in any of the forums I reviewed. Note - According to Hyundai, the part is not that difficult to replace *if* you can get the T30 torx bolt (I think that is the spelling) out without stripping it. You would most likely need to remove the sensor as well because it is a tight fit.

This blog is helpful... my 2011 accent has been doing this since I bought it last year, with only 50K miles. Very frustrating and I didn't expect to dump $1,000 into a new car to me. I had to replace the platinum plugs twice in the last 6 months and now all four coils. This car is getting sold since this is a common problem with the hyundai, I sure won't recommend to anyone.

My 2000 Hyundai Sonata GLS has been jumping and skipping for around five to six years now. When it starts jumping and the check engine light comes on I can stop my car and turn it off and back on and it stops. I have changed the platinum plugs and wires more than I can count. My 17 year old daughter will soon be driving this car to high school and college daily after repairing it and doing some regular maintenance on the timing belt and water pump, since I had it break on me before and it cost $1000 to fix it. If anyone can help me figure this out please contact me through my question on here. No one has answered on my question yet. This car has been good to me till now and it has a lot of memories attached to her. I would like to keep her around for a long time. Anyone that can help me please let me know? Thanks, Melissa 2000 Hyundai Sonata GLS 6cyl Aka... Diamond... My email contact info... melissa421980@yahoo.com I also posted my problem on here months ago but no one has responded yet. Thanks everyone. I don't want to loose this car and her memories so if anyone can help please find me on here or email me ASAP. It has to be fixed for my daughters ASAP so she can get to school and college in August. Thanks Again...

I have a 2005 Sonata. I have sunk a bunch of money into. Still not right. NO MORE HYUNDAI FOR ME. The dealership not the factory would guarantee a fix but still wanted paid for it. Was considering a new one, but it will not be a Hyundai.

if replacing the o2 sensor make sure yo get he right one for your car I didn not know Hyundai made 4 ,5 & 6 prong fittings for the same year car ---- I ordered the wrong one ( an MTK 25606 and it was supposed to be a 23403 ) now the Whitney catalog is giving me a hard time about returning it,

I was going through the same thing with my 2003 sonata. Had the plugs and wires changed twice in 5 months but still misfiring like crazy. Finally when I went in the last time they found the issue. It was the fuel pressure regulator that had gone bad and was pumping way too much gas into the cylinders. About a 70.00 part. Total cost out of Hyundai was 278.00. Runs like a dream now and better gas mileage. At first they thought it could be a bad coil but that wasnt it in the this case, You might check that as well.

I'm having that same problem,tring to get to the root of the issue,the car has been in the garage for 10 years,it had a bad fuel pump,and wouldn't start.got fuel pump changed ,and now it's running rough and hesitates when I push on the gas,but it also has a noise like the coils.

The guy that said the tensioner replaced is right. You have to either way replace timing belt. With that you have to readjust the timing marks and either tighten the tensioner which is what i did or just replace it. Either way its tightened. Iam a girl. I did it. All by myself. Yay. But all of these are what my car was doing and mine runs perfect now guys.......

Btw mine is a 2.7, 2005.

Ive also had my coil packs replaced a while back. It helped some. But now its perfect. Look out for the suspension next folks. Replace your shocks after this and it will go another 100,000 or more with proper lube changes. Keep it. Its worth it! The work is not that hard. I youtubed it.

I have a 2004 Sonata GLS. I spend more time in these forums for this car than any other car ever!! I fixed my horrible misfiring and hessitation by reading in here to start the car, open the hood, and spray water with a spray bottle over the plug wires. I did it at night so it was dark enough to see. WELL, it lit up like it had blue and white worms . I replaced the wires, and since I had to take off the plenum to get to the back ones, I replaced the plugs too. My car run like a snail, but it always did. It's sweet for a hyundai.

Did anyone replace the electric part of your throttle actuator or even the entire throttle body?

Ok. Ive read through as many of all of your answers as i could. Has anyone researched this cars greatest sin? There was a little known problem that the manufacture initially tried to cover up. It cost me a $3000 repair to find this problem. When the Sonata was built the assemblers processed the line with one process out of order. They painted the body without masking the grounding surfaces first. This didnt appear to matter because no one had discovered the problems that the cars were having multiple issues related to this. But, now all of these issues are pointing to the chassis not being properly grounded. Ask yourself these few questions.... Do you often get a static shock when you touch your door when getting out of the car? Does your battery need replacing every couple of years? Is the battery always swollen when replaced? Does your temp guage randomly go up or down. Does your car hesitate, then run fine, does it just not start, then suddenly run fine. No car repairs itself. So, if your car is at anytime running fine after it has a problem, then your car doesnt have a mechanical problem. It has an intermittent electrical problem. If not addressed, then you will see the failures become permanent. All sonata owners should have this checked before any other money is spent on other repairs. I had my 2004 GLS until 1 year ago. The car was one problem after another, all were associated with a bad ground issue. 3 years ago, i met a man who worked at Hyundai in Korea. He told me about this issue and told me that american dealerships knew about this. You have to tell them to fix it or you will almost never will get them to acknowledge it. They will try to charge you upwards of $900 to diagnose it unless you threaten to contact JD powers. This repair only cost you the price of 4 or 5 grounding straps. They wont tell you where they go unless you ask them. Ask them!!! They left one loose on mine so problems continued for two more months until i found it myself. After that, i had zero issues for 3 more years until i sold my car to a friend. She loves her Sonata to this day. I felt i needed to share this with all of you because i knew no one else would. Good luck to everyone.

Ok. Ive read through as many of all of your answers as i could. Has anyone researched this cars greatest sin? There was a little known problem that the manufacture initially tried to cover up. It cost me a $3000 repair to find this problem. When the Sonata was built the assemblers processed the line with one process out of order. They painted the body without masking the grounding surfaces first. This didnt appear to matter because no one had discovered the problems that the cars were having multiple issues related to this. But, now all of these issues are pointing to the chassis not being properly grounded. Ask yourself these few questions.... Do you often get a static shock when you touch your door when getting out of the car? Does your battery need replacing every couple of years? Is the battery always swollen when replaced? Does your temp guage randomly go up or down. Does your car hesitate, then run fine, does it just not start, then suddenly run fine. No car repairs itself. So, if your car is at anytime running fine after it has a problem, then your car doesnt have a mechanical problem. It has an intermittent electrical problem. If not addressed, then you will see the failures become permanent. All sonata owners should have this checked before any other money is spent on other repairs. I had my 2004 GLS until 3 years ago. The car was one problem after another, all were associated with a bad ground issue. 3 years ago, i met a man who worked at Hyundai in Korea. He told me about this issue and told me that american dealerships knew about this. You have to tell them to fix it or you will almost never will get them to acknowledge it. They will try to charge you upwards of $900 to diagnose it unless you threaten to contact JD powers. This repair only cost you the price of 4 or 5 grounding straps. They wont tell you where they go unless you ask them. Ask them!!! They left one loose on mine so problems continued for two more months until i found it myself. After that, i had zero issues for 3 more years until i sold my car to a friend. She loves her Sonata to this day. I felt i needed to share this with all of you because i knew no one else would. Good luck to everyone.