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Discussion Starter · #1 ·
Last Saturday I had the oil changed at the dealer on my 2011 Santa Fe Limited V6 3.5. As I left the lot, I noticed knocking and reduced power. I went back in and they took it out for a drive and it was gone. The engine had been turned off and back on when before they went out. I went out with them again and it was gone.

Today I drove about 10 minutes, stopped and turned it off for about 10 minutes, and when I started it again and drove off, the knocking was back. It lasted about 5 minutes in stop and go driving. I might have been imagining it, but it didn't seem to completely recover until I turned off the engine and started it again (about 10 minutes in).

What can I do to narrow it down? I don't know what it is, but when I try to think what the symptoms are like, it's as though a cylinder is not firing. So far it has only happened twice and the first time right after an oil change. It has 50,000 miles on it if that's relevant.
 

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You say this has happened twice, though you seem to be saying that the last time, it was also associated with an oil change. Please advise whether I've got that correct, and if so, do you have any sense as to why it stopped? Was there any power loss associated with it that time? How sure are you about the power loss this time?

When you say "it's as though a cylinder is not firing" and you are using the word "knocking" together, it's creating difficulty in understanding what you are hearing.

We really need to work on the word "knocking" and your prior experience to see if we can get some focus on this.

Do you feel confident that you could correctly identify the sound of what is normally called 'engine knock'? This is a pre-detonation of the fuel within the cylinder, causing the fuel to explode too early in the cycle. It's more of a sharp rapping sound than a 'knock' as we'd normally use that word. Your ECU should be managing this issue, and you should really never hear it. However, a significant mis-timing of the firing will cause power loss as you described. However, an oil change should not have any impact on this sort of thing. Please advise if you have experience with this sound from your history, and whether this is what you mean.

Do you feel confident that you could correctly identify the sound of lifter noise? This sort of 'top end' noise is a more of a tapping sound, most often occurring immediately after starting the engine, and a little bit of this (10 seconds or so) is not uncommon for a Santa Fe. This sound is related to either lubrication or lash issues in the valve train. An oil change could have an impact on this type of noise, especially if there is significant leak-down of the oil due to a filter issue. However, you should not be sensing any real power loss. Note that a serious leak-down issue isn't common with a dealer change because the dealer is most likely using a Hyundai filter. Leak-down issues are most commonly associated with aftermarket filters. So far, we've seen no problems with the ones with yellowish paper marked "Made in Korea" no matter where they've come from (probably all the same factory). However, if the problem persists, it is possible your dealer has some bad filters. Please advise if you have experience with this sound from your history, and whether this is what you mean.

Last, we get down to uglier things like rod knock, piston slap, and other bottom end types of noises that are NOT good. They are often much louder than what I've described above, and will have a much deeper sound .. not a high pitched tap or rap, but a lower pitched sound. Typically, once they start, these noised do NOT go away, and are due to worn rings or bearings. So if your problem finally resolved itself, it's unlikely that you're hearing this. Please advise if you have experience with this sound from your history, and whether this is what you mean.
 

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Discussion Starter · #4 ·
Thanks for the detailed reply. I'll clarify the timing. I had the oil changed on Saturday. That was the first time (ever) I had the symptom (immediately after the oil change). The second time was today. The first time it happened, it stopped after the car was turned off and back on (as far as I can tell). The second time (today) it seemed to subside on its own after about 5 minutes.

Maybe ping is the proper term. Here is a link to a video that sounds similar. The best example is about 1:40 into the video.

There is a loss of power when it happens. Not much, but noticeable.
 

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OK, now that we're 100% certain this isn't just a startup lubrication issue (that's a common complaint) -- you really need to get that back to the dealer for evaluation, especially since you CAN identify a real power loss, however minimal, when this occurs.

Meanwhile, DO check to see that your oil level is correct! While rare, you wouldn't be the first person to have left with a short load of oil, and you really do NOT want to be driving around that way. I'd also have them take one more look at the filter itself.

There's nothing done during an oil change that should have disturbed anything that is related to pre-detonation (knock), but the fact that's it's there at all is problematic. The ECU receives signals from two knock sensors on your engine that cause it to retard timing if a knock is detected. These should kick in before the knock is really noticeable to you (they're supposed to be more sensitive than your ear!). Retarded timing due to a knock on any cylinder will decrease performance for the rest of them. In addition, if the condition is severe enough that the problem can't be controlled, or one of the sensors is bad, it should be throwing a code (likely P0326 or P0331).
 

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A 'pinging' style of knocking is as I described earlier. Mechanically, the air/fuel mixture is being fired off early for some reason.

This is caused by ignition that occurs earlier than is appropriate either due to spark timing, a lean mix, or deposits so hot in the chamber that they fire off the fuel before the spark plug has a chance to fire. 'Appropriate' timing is based on a number of factors, including fuel octane rating, compression and overall combustion chamber temperature (partly a function of compression ratio), manifold pressure due to engine load, RPM, deposits in the combustion chamber, air/fuel mix, and a host of other things.

Mechanically, if you've got a problem with either ignition timing, lean mix, or hot spots in the cylinder that is causing the fuel to ignite early, the resulting explosion is starting to push back against the piston too early while it's still traveling up. Since there's a finite time required to really get the fuel burning, it's normal to start the ignition prior to 'top dead center' (top of the piston travel), but you can't start too soon or you've got the crankshaft trying to push the piston up while the explosion is already trying to push the piston down. The shock wave created by the two causes the 'pinging' sound.

What's more important in these cases is that there is additional stress being placed on all of the piston components - piston, rod and crankshaft and their bearings. Too much early ignition also makes a cylinder run hotter, and destroy parts.

OK - for what it's worth .. it's rare, but running an engine with little or no oil CAN cause pre-ignition detonation due to much higher than normal resulting temperatures in the cylinders due to lack of lubrication. So for heaven's sake, do check your oil level, and make sure there's else obviously wrong there.
 

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Discussion Starter · #10 ·
They checked for codes and there were none. Coincidentally, when I was leaving the symptoms recurred. I got the guy back in the car to hear it and he suggested it was just bad gas.
 

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That is a possibility, but it would have to be some really bad (low octane) gas, and it seems odd that it wasn't doing this before you arrived at the dealer the first time, but seemed to be as you left. Then again, nothing they did should be causing this anyway. What was the history of any gas fills shortly before or after that first visit?

Just as an aside, and a bit over simplified, but ... low octane gas actually burns more readily than the expensive stuff. The higher octane fuels are designed to resist ignition so that they don't pre-ignite due to the heat created during compression in higher compression engines.
 

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Discussion Starter · #12 ·
I filled with 87 octane last Friday (day before the oil change) at one of the two places I usually go for gas. I go to that place about 20% of the time and another (same company) 75% of the time. It's been the same tank of gas since the problem started. I just filled again today - 13 gallons - with 93 (right after the dealer visit) at a station I've never been to.
 

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The move to 93 octane may mask the problem, but it will be interesting to hear whether you have any more incidents. Keep us posted. If the problem recurs, you'll want to report this to the dealer right away for documentation purposes.
 

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Discussion Starter · #14 ·
In about a week, I'll be back to 87 and I'll see what happens. By then I'd think any argument for bad gas would be out the window.
 

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Discussion Starter · #15 ·
Update

In the last 4 days I've had two instances of odd noise at startup. This occurred today and on Sunday the first time I started for the day both times. Garage temperature is a pretty constant 80 degrees so I don't think temperature has anything to do with it. When I start it, it sounds almost like a diesel engine. That's the best comparison I can think of. The first time, I drove for one mile, stopped, turned the car off and restarted it. The sound was gone. The second time (today) I drive for about 3 miles, stopped, turned the car off and restarted it. The sound was gone. The computer in this doesn't run on Windows does it?:whistling:

This is not a noise I've ever heard from the car before. I'm still on the new tank of 93.
 

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Put a can of seafoam in a full tank of gas or some other type of fuel injection cleaner. It could be bad gas but after 2-3 tankfuls, should go away. double check oil is not low is a no brainer. If condition persists, go back and ask them to replace the oil filter with a new one. If the 3.5L V6 model, the oil filter is on top of engine so only going to loose about 1/2 qt. of oil at most and then dealer can top off the oil again.

Who the F knows, maybe dealer forgot to put an oil filter in the housing? Wouldn't surprise me one bit. Had a dealer do a TSB before on steering wheel linkage/bolts to make sure they are torqued to spec, next few days afterwards the whole steering wheel fell off while my wife was driving down the road. Explain that one to me when I went back to that dealer after getting it towed to another dealer who did admit that dealer F'd up, they got 10 earfuls of me and haven't been back since and never will.
 

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I'd sure be back to the dealer with that ASAP. I'm not saying that it IS, but it sounds like the top end is oil starved on first start, and something odd happens when you stop/start the engine again later that remedies the problem.

After about the first 15 seconds from start-up, any tapping noises in the top end of one of these engines that are more than barely audible are abnormal. Most of us are familiar with them ONLY at start-up. We just don't hear about them persisting, which is what's troubling about your report.
 

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Discussion Starter · #19 ·
While searching for sound samples to play for the dealer, I found this. This is the most recent sound. Last happened yesterday.

 

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Holy crap -- that sounds positively dreadful! Like anything of this sort, there's nothing like hearing it first hand, but that had some really nasty top end noise. I hope yours isn't that bad.
 
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