Wife's car is a 2007 Sonata 4cyl with 150k miles. Except for last week it has been a pretty trouble free ride.

Wife starts the car to move it to a different place in the driveway. It stalls, then won't idle. I try to get it to run, will only run if you keep the rpm's up over 2k. As soon as you let off gas it stalls. Wife is not sure if plugs had ever been replaced. I had a new set in the garage, was just waiting for a warmer day to replace them.

Next day it is reasonably warm so I replace the plugs. Old plugs are black as coal. I'm hoping that is the problem, but it is not. It will idle longer this time, but still violently and will stall and you can smell gas. Funny thing is the check engine light does not come on.

I disconnect/reconnect the battery and try it again. No improvement, but now check engine light is on. I look for my ODB2 adapter to check out codes, can't find it.   I'm also not sure if the problem might be gas related.  Wife tends to buy gas at the cheapest places she can find it and a few days before she bragged about buying super cheap gas from a grocery store gas station. I put a can of dry gas in the tank and let it sit for a while.  Try to get to run a few hours later with no luck. Since I cant get it to idle, I have it towed to the shop.

They have it for a few days. Say they cleaned the MAF sensor and throttle body. Checked fuel filters and pressure. They get 2 codes, P0101 Mass Air flow circuit problem and P0016 for crank position/cam position. They tested the MAF sensor and said it was within spec. They manually tested the crank position and it was fine. They said the car will idle, just occasionally it will sputter for about 15 seconds when started and that will throw the P0101 code again.

I took the car home. I bought a new ODB2 adapter and plugged I drove it around for a couple of hours. Upon full acceleration I got another code, P0103 - MAF circuit high input. It did not trigger the check engine light, but showed up when checking codes. I also got the P0101 a half dozen times when starting the vehicle up, after it rough idles for about 3-10 seconds.  This rough idle appears to be random, does not matter if the engine is hot or not.

I'm thinking of replacing the MAF sensor even though they said it checked out.

Has anyone had to replace their sensor or had a problem similar to mine that can shed some light on a possible solution?

DISCLAIMER: Im not a mechanic.

The shop didnt say anything at all as to what the problem is? Sounds like a bunch of clowns.

Get some CRC MAF sensor cleaner, pull the MAF and carefully pull the electronics from the housing and clean it with the cleaner and -qtips. Gently. Just from the symptoms you've posted, it does sound like your MAF sensor is bad/going bad.

The CKP code does confuse me though. Are you still getting it?

They said they cleaned the MAF sensor, but just to be sure I also cleaned it yesterday.  Drove it after cleaning it and still get the MAF codes.  I have not had the car throw the P0016 code for crank position/cam position.  I have had it throw a code P0011 for timing over advanced on bank 1 the first time I drove it after picking it up.  It did not throw that code the last two times I drove it.

Out of concern that she got some really bad gas I did fill up the car with premium from a BP station.  I also put some 44K in there.  I have driven it around for 4 hours and the wife took it to work today, which is an hour drive at highway speeds one way.

Well,

If the codes remain and you decide to go with a new MAF, consider the Beck/Arnley 1580805 from Rockauto. Its $140.79 + shipping and with the 5% discount code should come right in at $140 shipped. Google for the 5% discount code.

Code P0016 first. This code sets when the camshaft is advanced or retarded to it's maximum limit. Your car has VVT (variable valve timing), The #1 cause for VVT codes is the oil itself. It may not have enough oil in the engine, oil could be the wrong weight (very important in a VVT engine) or the oil could be dirtier than Obama. #2 cause for P0016 is the VVT solenoid. It has very small passage holes and fine screens in them that get clogged when the oil is not changed on time. Proper oil and maintenance is critical for a VVT engine. P0011 is also related to the VVT system. More than likely one fault causing both codes.  If the oil is dirty or it's been awhile I'd start with an oil change.
P0101, P0103 are MAF codes. You may have a MAF sensor going south on you but from my experience they are pretty reliable in the Hyundais. If you have a large rubber boot going from the MAF to the air cleaner housing, check that boot/huge hose first. Any holes or cracks will allow unmetered air to enter the engine and confuse the ECM.  The ECM will add lots of extra fuel to compensate for the lean exhaust condition it sees from the oxygen sensors. If that rubber boot is in good shape, or non-existent because the MAF mounts directly to the air filter housing, then you may have a bad MAF.

Just as above check for any un-metered air leaks including vacuum leaks anywhere.

It's funny that you mention the Hyundai MAFs being pretty reliable because a lot of people use a Hyundai MAF on some BMWs

The crank sensor, if bad, will mostly not let you start the car at all, but it COULD also be the cause of the stalling.

That is true but I think the OP got mislead by the code description because he said " P0016 for crank position/cam position".  P0016 is a VVT (camshaft position) code, not a crankshaft code.

Ah I see, guess I skimmed past that part. Op you mentioned smelling gas, is that still happening? Were you able to pinpoint it's origin?

The oil is clean, but, it is not the preferred weight.  The owners manual recommends 0w2w, but indicates 5w30 is ok to use also.  They did not have any 0w20w last time I changed it, so I went with 5w30w.

There is a rubber boot that goes from the air cleaner to the throttle body.  I did not notice any cracks in it when I cleaned the sensor, but then again I was not looking for any.  I will pull it off again and thoroughly inspect it.  

I notice there is a PCV valve on this engine, if that is clogged could that be interfering with the air flow?

I never saw the P0016 code.  That is what the shop wrote on the work order.  I have not had the car throw that code for me, only the P011 for over advanced timing, and then only during the first two hours I drove it after picking it up.

I don't smell gas anymore.

Alright well that's good actually. Probably means that you just smelled it because it was running rich for a bit while it was struggling.

If the MAF is bad or is sending the incorrect signal, then that could be why you smelled gas. Essentially, the MAF controls your fuel / air ratio.

As for the PCV valve, most of the time that will make your car run rough. But you seem to have other symptoms and most of the time a bad PCV won't throw any codes.
Cracks in the intake boot will be hard to see so make sure you squeeze it while you look to find any possible separation points.

Have you cleared all the codes and driven the car and rescanned? Probably a dumb question but sometimes people just forget to clear the codes.

Try this, it refers to what the other poster was saying about the VVT. The OCV is like the control solenoid for the variable timing.


If both tests pass then your OCV should be fine.

The exception to this would be if it is coated with sludge. If it is coated with sludge there is usually no point in trying to clean it because the passages are too small to get clean.



 

Just checked the air pipe from the sensor to the throttle body.  Don't see any cracks or holes.  I guess I'm just going to buy the sensor and see what happens.

If your scanner shows you a PID for " Engine Load" or "Calculated Engine Load" watch it to see if it goes over 90% during wide open throttle.  Just get on a straight road and in drive, then step on it like you just stole it. Engine Load should show over 90%. If not suspect bad MAF. Not unheard of on those models.

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I'm using Torque Pro.  It will let me choose a display for engine load, but it is not active.

Thanks, but I can get one a little cheaper from a local place called Bap-Geon.  Been going to the for years.

So I let the wife take it to work and she calls me saying it won't run when she goes out to lunch.  I told her if it runs rough just get it up to about 2k rpms for 10 seconds and it will settle down.  Someone at work helper her start it.  When she got home I pulled the codes, same mass air flow code.  It also stalled on idle for me.  

Out of curiosity I'm going to pull the plugs today and see what they look like.  I know the plugs I took out were 50k miles over the limit, but they also should not have been so fouled.  I'm curious to see if the new plugs are starting to get fouled.

Smell them too, if they have a strong smell of gasoline then it's running rich and could be another symptom of a bad MAF.

Plugs were starting to foul already.  They smelled of gas and there was carbon around the outer ring of the plug.

Either running rich or you're not getting spark (or you have a weak spark).

I'm leaning towards running rich, which could be the maf, especially since you have error codes related to the maf

Update:  Just installed the new MAF.  That seems to have fixed the problem.  It is 40 degrees here today.  When I first started it I noticed the engine revved up to about 1400 rpm's for about a minute.  This is normal in cold weather, and it dawned on me that it was not doing that with the old MAF.  I drove it around until the engine was to normal operating temperature.  I shut it off and started it again and no rough idle. Did not throw any MAF related codes.  I then put the plastic engine cover back on and waited a few minutes.  Started it again and it idled smooth.  Going to drive it around more tomorrow to make sure it is ok.

Thanks for all the advice!

Glad you solved the problem. Thanks for actually providing enough info for people to help