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2004 Hyundai Sonata Stumbles And Stalls...Need Help!!!

fdegree fdegree
New User | Posts: 1 | Joined: 08/08
Posted: 08/06/08
12:28 PM

2004 Hyundai Sonata - 4 cyl. - Automatic Transmission

I am now completely puzzled. This problem started over a month ago – spark knocking, lurching, minimal response to accelerator positioning, occasionally stalls…almost like it is running out of gas. But, it would not do this all the time…sometimes it would run for a few days just fine, then out of nowhere, it would start giving me this problem.

At first I thought it was water in the gas since the very first time it happened was 20 minutes after filling the tank. So, I tried a gas additive to get rid of any potential water in the fuel tank over the course of 3 tank fills…didn’t help.

Found out I needed a special adaptor just to check fuel pressure.  Since I didn't have one, I decided to just replace the fuel pump and spark plugs…didn’t help.

Started to notice it was happening more frequently (now daily), but always after about 20 – 30 minutes of driving. Let it sit and cool down for a while, it would be fine until it heated up again. The engine temperature never overheated…stayed around 205 – 210 degrees.

During the course of all this we found codes for the cam sensor, cylinder 1 misfire, cylinder 4 misfire, random misfires (I don't remember the actual code numbers now). Then, one night, I cleared all of the codes and restarted the engine. Revved it up until it started acting-up again, so I could recheck the codes…did this 3 times. Each of the 3 times it only returned a cam sensor code, nothing else. So, I replaced the cam sensor (which was only 8 months old…it was replaced back in November)…didn’t help

Most recently, the engine "stumbled" and eventually stalled, after about 20 minutes of driving. Checked the codes, and it returned only 2 codes:
P0421 - Warm up catalyst below threshold bank 1
P0340 – Cam position sensor A bank 1 ckt malfunction

Out all of the times it has been acting-up and returning codes, this is the very first time we have seen the catalyst code. Although, the Cam sensor code seems to appear every time.

Checked ignition coil and plug wire resistance...nothing odd with them.

To summarize:
Runs rough and stalls after 20 – 30 minutes of driving
Tried gas additive to get rid of water
Replaced fuel pump and spark plugs
Replaced cam sensor
Nothing has solved the problem

Any suggestions…  

docfancy docfancy
New User | Posts: 1 | Joined: 09/08
Posted: 09/02/08
08:30 PM

I have the same problem. It had gotten really bad a month ago. I checked and replaced the PCV valve, which made an immediate improvement, but did not fix the problem. I am going to clean the throttle body next.
I have a 2000 hyundai with 133,000 miles on it.  

toddgest toddgest
New User | Posts: 1 | Joined: 10/09
Posted: 10/14/09
10:44 AM

Any luck with getting this resolved? My Sonata is starting to act up as well. I have not replaced any sensors or other parts. But before i plunk down some 90$ for a diagnosis that may or may not replicate the problem...
I was wondering if you found out anything?

SedesGobhani SedesGobhani
New User | Posts: 2 | Joined: 11/09
Posted: 11/23/09
08:03 PM

Sure sounds like vapor lock if it only happens when it's hot.  That's when there's not enough insulation between the fuel line and something hot like the exhaust manifold.  But it may be a fuel filter.

My 2004 Sonata engine just started stalling and stumbling for the first minute or two after every gas fill, then it's fine again until the next gas-up.  I am clueless.  

odell79 odell79
New User | Posts: 1 | Joined: 12/09
Posted: 12/29/09
02:31 PM

The same happens for my 2004 sonata, but only if I let the tank get down to the point the warning low fuel light comes on.  I went to a mechanic and he said it has to do with the amount of pressure on the fuel pump and his advice was to fill the tank when it gets down to the 1/4 level.  Don't know if this helps, but I am going to try it.  

antman59 antman59
New User | Posts: 1 | Joined: 01/10
Posted: 01/13/10
12:01 PM

I have the same issue with our 2004 Sonata.  It started in December but seemed to be worse Today.  I even took it to Hyundai who kept it overnight and did not find any issues.  Their is no engine light to indicate a problem.  It's good to see what people have tried so far though.  

jhalter23 jhalter23
New User | Posts: 1 | Joined: 03/10
Posted: 03/07/10
09:03 PM

Anyone get this problem solved? Just had almost the identical situation happen.  After driving on the highway, it starts then dies.

Dealer replaced crankshaft (I think) sensor and I still have the problem.  Any solutions would be appreciated!  

waynep7122 waynep7122
Addict | Posts: 4545 | Joined: 08/09
Posted: 03/07/10
11:34 PM

i would bet that taking off the throttle body.. and then the idle speed control motor and valve and cleaning it.. would solve problems..

it will probably need to be replaced...  as the one i looked up for a 2004 sonata 4 cylinder is plastic..

here is a picture of what it looks like...  you will have to copy and paste the link...

this has a small motor that turns a shutter blade to control the amount of air bypassing the throttle valve... this is how the computer controls the idle speed..

carbon gets on the shutter blades and causes them to stick and hang up..

you might try spraying through some rubbing alcohol.. or giving a short blast of brake cleaner..  you might test the brake cleaner on the outside of the valve first.. make sure it does not melt the plastic..
this is the cause of a lot of idle stability problems..    sticking at fast idle.. won't start without touching the gas pedal..

for those with 96 and newer cars....  buy one of these

if you can afford it.. it displays live sensor data... and trouble codes..  also graphs sensor voltages.. to look for bad spots..

it will pay for it's self in 2 uses...   the other models they have are not as good and don't do all this.. i have a 98614.. and its almost impossible to fix cars without it..   it will also turn off the check engine lights...  

AUTOnomous64 AUTOnomous64
New User | Posts: 1 | Joined: 03/10
Posted: 03/31/10
08:00 AM

I had a similar experience and the Hyundai repairman indicated it was the PURGE VALVE.  I'll send an update if the problem continues as I plan to pick up my car from the dealership today.  

SedesGobhani SedesGobhani
New User | Posts: 2 | Joined: 11/09
Posted: 05/03/10
11:33 PM

yep that's what I saw in another forum a couple months ago.  Purge valve is somewhere behind the fuel injector unit and if it goes bad then you can't start car just after filling fuel tank.  Let us know if it helped.  

vegascoach vegascoach
New User | Posts: 3 | Joined: 06/11
Posted: 06/23/11
11:57 AM

Just this past week my 2003 Sonata did the very same thing. Lat week in Las Vegas, ambient temperature was 105 degrees.  First time happened after driving about 5 minutes to get to the highway, and then another 5 minutes on the highway where it lost power by way of engine miss and graduated to sputtering and loss of power and it died.  Would not start up immediately. NO OVERHEATING; GAUGE BELOW HALFWAY MARK.
While waiting for tow (maybe 10 minutes)it started and I nusred it ioff the highway where it stalled again on off ramp. Waited another 5 minutes and started again and got it to a gas station and waitied for tow truck. Car was in shade and idled beautifully with AC on.  Had it towed to my mechanic who checked codes, fuel line /fuel filter / fuel pump , etc.  - he found nothing.  Drove the car 4 miles on surface streets to Hyundai dealer.

They did all the codes, etc, and drove the car 26 miles - nothing.  Picked car up, drove it around for 3 days until yesterday Tuesday the 22nd.  Driving on highway in 110 degree heat, spurrered and stalled again.  died on side of highway.  same as before; nursed it to a grocery store parking lot. While looking under hood, the engine backfired 3 times, almost in succession, while idling. picked car up 2 hours later. Dove home on surface streets without incident.

A NDOT highway courtesy vehicle had followed me to the grocery stote; he saw nothing but did hear the backfiring; he thought it could be a vapor lock issue or sensor issue that is only showing up under extreme heat conditions.  Highway driving and 105 dgrees.

Anybody figure this out yet?  

waynep7122 waynep7122
Addict | Posts: 4545 | Joined: 08/09
Posted: 06/25/11
07:27 AM

vegascoach..  you did not say if you have the 4 or the 6 cylinder motors..

thermally related failures are hard to diagnose...

there is one thing...   most scan tools have a record data setting... with 2 ways to activate it...   start the recording when the check engine light code is set.. or a manual start recording..

when the scan tools are set to record... they are actually constantly recording the data stream.. when you push the button.. it saves the prior 5 seconds or more of data stream and the 5 seconds after you pushed the button.. so you can go back and review the data stream watching for changes...

i probably would start with a crank shaft position sensor...
the 4 cylinder version...

the 6 cylinder version..

neither of these are cheep... but they are less expensive than any of the other parts  and are likely to fail at extreme high temps...  then possibly recover like you describe...

there is a chance that you have gotten the last of the winter fuel...  not likely.. but a chance... and it can boil in the fuel lines...

on the 6 cylinder motor.. i would also visually inspect the ignition coils... look for    dust circles or white dots on the circular part near the laminated frame..

with the 6 cylinder one can also clip on a timing light and monitor the spark with a timing light under the wiper with the trigger taped on.. if you can get the hood closed with the wires through the gap...

since you did not describe which motor.. i am going to suggest that you check the TSB titles over at     its free for the titles...  see if there are any that describe your problem..  

vegascoach vegascoach
New User | Posts: 3 | Joined: 06/11
Posted: 06/26/11
11:36 PM

Thanks for your response. It is a 6 cyl.   the dealer checked all of the TSBs against my VIN - nothing came up.  I will throw your suggestions at the dealer service guy and let you know what he says. FYI - I've been driving the car on the surface roads and avoiding the highway.  We did drive it to California from Vegas without incident 2 moths ago. Much cooler temperatures.  Seems odd that the identical condition one week apart cused the engine loss of power and stalling. Dealer could not re-create the condition. Thanks!  

vegascoach vegascoach
New User | Posts: 3 | Joined: 06/11
Posted: 06/26/11
11:41 PM

Did you find out what was wrong?  My 2003 sonata stalled 2 times a week apart on the highway here in Vegas.  First time it was 110 degrees outside and second time 105 degrees.

when it is colloer, no problems

Any advise?  Or, did you find a very reliable Sonata expert somewhere?

Any help is appreciated. Laugh  

waynep7122 waynep7122
Addict | Posts: 4545 | Joined: 08/09
Posted: 06/27/11
12:25 AM

if there are NO codes...

and the engine stalls.. when really hot..

its still probably the crank sensor..

its probably a good idea to get it changed.. be sure to ask up front for the oil part back...   or have it done where you can see it being done...

its the most likely suspect.

do you have a harbor freight tools nearby...

the 98614  scan tools can be had for about 120 bucks and tax..

with them .. you can plug it in when it fails...  examine the various sensor data streams... see if the crank sensor is putting out the proper info... i have not tried it on a sonata... but you might be able to graph the crank sensor signal..

not all scan tools will display live data streams on OBD cars.. this one will...  

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