03 sonata, 2.4 L engine hesitation off idle cold or hot. 3 remanufactured maf sensors, good fuel pressure, new wires, new plugs,new coils, new timing belt, rechecked timing specs. car sometimes falls flat on its face, then will accel. when passed the initial hesitation will run fine. does it most of the time. has appox 80000 miles on it. unplug maf and car seems to run better. any ideas? this thing is really testing my patience

 

Have you check the throttle position sensor?

 

going to do that with a multi meter directly off the switch. my scanner does not react fast enough, when watching it thru the pcm

 

check the throttle position sensor , working perfectly. ordering a new mass air flow from Hyundai tomorrow. driving car now with it unplugged

 

well the new mass air flow sensor help but not total fixed. any ideas?

 

I have a 99' Sonata with the 2.4L 4cyl and I have the EXACT SAME PROBLEM! I unplugged the MAF today and it runs great. I put in an engine with 29000 on it. It now has 45000 miles on it. I have many spare parts. I have swapped the MAF back and forth 4 times. Every time I do the car runs like new for either several hours or for a day or two. I am severely perplexed.

I did read somewhere the MAF could have a bad ground. Something to check.

Now it may be possible that since one of my codes is a lean condition (i do not have an exhaust leak or a vacuum leak) that by unplugging the MAF the ecm then rich-ens the fuel mixture to compensate not knowing the air flow. Thus a better running car.

ECM need reprogrammed?

Is it possible to have a plugged catalytic converter and cause these same issues???

Good luck to all having this problem!

 

challenger,

I worked on mine again last night. I have 2 sensors (MAF) to work with. I cleaned them both. The one in the car after cleaned would cause the car to cut out severely upon acceleration. Step out unplug the sensor jump back in and the acceleration is smooth and crisp. Plug sensor back in, right back to the stumbling. I never even shut the car off. I left the hood open and just drove back and forth about 10 feet. I installed the second sensor, started the car and it ran rough and the idle floated up and down a few hundred rpm's for about 5 to 8 seconds then right to a steady idle. Backed up no stumbling. Shut the hood and went for a 12 mile drive. Runs good. For some reason it seemed to run excellent and have more power with the MAF unplugged. Can't complain though everything is smooth. Wife went all the way to work and back (55 mile round trip) and the car didn't miss a beat. Now we will see how long it lasts. Check light is still lit, I believe the car has to see no error for so many starts before code clears.

Is your car still running good after the new sensor?

I forgot to add when my car runs bad and falls on it's face, the shifting is all screwed up. It's the weirdest thing. When it runs good the shifting is perfect. Did you have this problem? Has anybody else seen this?

 

i have a simaler problem (just posted on it) all started when got a cold air intake (built myself) and got alot worse when i shortend it, wonder if they are just cheap MAF, try looking into an anftermarket MAF if it exists