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My 06 Sonata runs very rough at start up when the car is cold. It appears that it is missing on several cylinders. This last for about 15 seconds and then the car runs fine. Any thoughts on what could be causing this problem? No check engine light.
 

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What engine, as it is not seen to left with the "DRIVES: 2006 Sonata"..

6 cylinder has a couple PCM upgrades you is likely missing, latest being NF 3.3 ECM UPGRADE K-LINE if you not have it, contains a wealth of jibberish for a host of items in the update..

Have you had the throttle position sensor replaced , as there is new style part, and program to go withthe part been updated to the program listed above.
 

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3.3 L engine. I haven't had any PCM upgrades that I know of. The car has been trouble free since I purchased it in 06. The throttle position sensor has not be replaced. 72K miles on car.
 

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Thanks that very interesting, because it acts like the timing is off. That's how rough it runs at start up for the first 10- 15 seconds. I have 70k on the car. Do you know if this would be covered under the 100K powerplant?
 

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QUOTE (Atky @ Sep 27 2010, 04:00 PM) index.php?act=findpost&pid=359201
Thanks that very interesting, because it acts like the timing is off. That's how rough it runs at start up for the first 10- 15 seconds. I have 70k on the car. Do you know if this would be covered under the 100K powerplant?
Powertrain, and I bet it would not be covered, until the Engine stops?
 

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I read though several posts and the TSB for the timing chain rattle. While my noise does lost about 10 seconds or so, it is not a rattle from chain slop. It is an extreme rough idle like the engine is not firing on all cylinders or the timing is off. The exhaust has a unburned gas smell.
 

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i had the same issue about 3 months ago..

i got the spluttering engine twice when trying to start it.. I had put seafoam into the car maybe a week before so it could have been that or a bit of bad fuel..

somewhat related; a few weeks later a part of the harmonic balancer had detoriated. That issue was noticeable by a clicking or ticking sound in the engine compartment. It was repaired during warranty..

hth
 

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QUOTE (jazzhands @ Sep 29 2010, 06:20 AM) index.php?act=findpost&pid=359556
somewhat related; a few weeks later a part of the harmonic balancer had detoriated. That issue was noticeable by a clicking or ticking sound in the engine compartment. It was repaired during warranty..
Ok, I've got a question then. While checking the ATF level a couple of days ago, so that I knew how to check it properly once I get my ATF flush next week, I heard some clicking/ticking noise coming from engine. It is coming from the top of the engine and I assumed it was normal valve noise and it did sound okay and not overly loud or anything. I am curious, is this normal valve train noise that I'm hearing? I really only hear it when the hood is open and it doesn't sound out of the ordinary. Where would the noise be coming from if it was the harmonic balance/timing chain tensioner/etc?
 
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