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Sonata 2008 GLS won’t accelerate properly


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gao7857
Novice

Dec 22, 2019, 12:27 PM

Post #1 of 7 (1093 views)
Sonata 2008 GLS won’t accelerate properly Sign In

I Changed full synthetic engine oil, filter and
air filter 12/17, rotated tires. Drove a bit locally
without issue. On 12/20, it was raining, the car did not
accelerate properly when entering highway.
After about 20-30 miles/hr, pressing down the
pedal won’t accelerate further. When press
pedal all the way to the bottom, still not
acceleration and the engine speed is just
2000 to 3000 rpm. When depress the pedal
can feel the car choke a bit. On the way back
via local, couple times it did accelerate to
about 40-50 miles/hour, if I slowly and gently
press the pedal. The temperature looks
normal. Engine light is off, so are other lights.
The car just passed its 150k miles mark.

Any suggestions what could go wrong?
Transmission? Brake paddle stopper?  Thank
you and Merry Christmas!


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Dec 22, 2019, 1:50 PM

Post #2 of 7 (1088 views)
Re: Sonata 2008 GLS won’t accelerate properly Sign In

All you can do is scan for any codes that might point you in the right direction.

Other than that is going to take some in depth diagnostic testing to look for something out of place at the moment the problem occurs.

It could be losing fuel pressure among other things like an electronic throttle failure.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



gao7857
Novice

Dec 23, 2019, 9:00 AM

Post #3 of 7 (1040 views)
Re: Sonata 2008 GLS won’t accelerate properly Sign In

Thank you for your time and suggestions. I checked couple things last night and the car somehow become running normal again. I will describe the details so not miss anything. Even though it seems runs again I still like to figure out what was wrong and fix it, so it does not come back again.

I checked the code although no engine light. No code. When I turn the key to on position the hissing sound was like before, indicating the fuel pump works at least, and maybe normally.

Turned the key to start, and found that the battery was low, so the engine is cranking but wont start, even when I pedal on for about 10 seconds. This reminds me (I forgot to mention) that on 12/20 when it did not accelerate properly, the battery was also low at start, but the engine was able to start when pedal on for a few seconds, and I drove out without waiting for the battery to be charged. I used the jump starter and the car started right away. When the car starts from cold it always has some cyclic grinding sound for a few minutes around crankshaft and camshaft, that I was believing to be due to the interference at cold temperature. This time I opened the hood and try to see if there is anything abnormal in that region. The car was running for about couple minutes and the grinding sound diminished as in the past.

I then stopped the engine. The battery red pole has no build up. I checked the air filter counter part. No debris from the air filter to the engine as I can tell, although I can not see the air entrance to the engine. The pipe seems clean. I removed the air mass flow sensor, and it looks clean too.

I need to get a fuel pressure gauge to measure the fuel pressure, and plan to check the catalytic converter the same time when I jack up the car. So last night I turns on the engine again without the jumper, and it started right away. I drove it out and everything becomes normal… I tried accelerate to 60 miles/hr and there is no hesitation of acceleration.

So the battery is my culprit and here is my theory. On 12/20 I marginally started the car with a low battery and immediately went on the road. The battery was still low, while I turned on the head light, the AC heater & defrost to high power, and also the stereo. The battery was barely charged when the car hit high way. So when I pedal up to enter high way, the battery cannot provide the power to the fuel pump to get more gas to the engine. Today when I went to O'Reilly I will also ask the battery be checked out, and probably get a replacement battery if confirmed. I will update when back from the store.

What do you think?


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Dec 23, 2019, 9:08 AM

Post #4 of 7 (1038 views)
Re: Sonata 2008 GLS won’t accelerate properly Sign In

I would agree that if the battery is weak, it needs to be replaced. Whether that is your actual problem is yet to be seen. Once the engine is running, even a weak battery would be fine with the alternator charging at full strength but change it and see what happens.

You will likely have to drive it around a while for the computer to relearn the idle strategy and other things after the battery replacement



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Dec 23, 2019, 10:03 AM

Post #5 of 7 (1031 views)
Re: Sonata 2008 GLS won’t accelerate properly Sign In

Quote ">
I then stopped the engine. The battery red pole has no build up.<"
That means nothing really but why did you say just the "red" pole? Both matter equally.
Any games or weakness of a battery can be checked, ruled out by testing what now matters is just how cold is it for this cold start? Real temp not some wind-chill thing.


That as a battery goes below 32F the rating of it new drops off for how powerful it is/was AMPS" wise for CCA rating is 32F only then gets worse.


I've harped on this an awful lot but if dealing with cold and expect to don't play with getting the most # of years out of a battery. It's never good in any place or time of year just that much harder sometimes on where you get stuck!


T



gao7857
Novice

Dec 23, 2019, 4:50 PM

Post #6 of 7 (1018 views)
Re: Sonata 2008 GLS won’t accelerate properly Sign In

O'Reilly checked the battery and the alternator. The battery is bad. The alternator is good. Replaced the battery and it drives good. I will drive and see for a few days and see if other things pop up.
What other things should I check? I can jack it up in my garage, but not a mechanic professional.

Thank you both and happy holidays!


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Dec 24, 2019, 6:22 AM

Post #7 of 7 (993 views)
Re: Sonata 2008 GLS won’t accelerate properly Sign In

Quote ">What other things should I check?<"
You asked: #1 is follow all service suggestions listed in owner/operator manual. Note that for most use the "severe" use schedule if listed that way.
Whether DIY or sent out there you seem good at noting what was done when is a great thing so keep that up.
Other and more is mark items or record (your call on this) with a "metallic Sharpie" is removable with a damp towel with some solvents despite marked permanent.


Things like date batter was new right on one or nearby!
* Could mark tires inside for location or under the hood for last known rotations by miles.
* If check mark down anywhere when brakes are checked what % left was noted if at all.
* Any and all filters on a routine schedule or not so you know at a glance when done last new.


Battery again: If not protected from corrosion you can and should yourself often plain WD-40 or longer lasting greases. Do include hold-down fasteners so they don't just bust off later it's a service item keep the thing simple to remove and put back.
Total other: Locks with a suggested product. Other latches for hood, hatches doors etc no need to fight with them or allow to wear out. Almost nobody does that and some items are nasty hard to fix or replace as dumb as a glove box can't keep the light out!


Good luck hope last work is the end of that try to prevent things as you can and always find out why something new makes a noise that's unusual to you,


T







 
 
 






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