You said fragments from the fuel pump have gone in the fuel filter. You did not mention If you have changed the filter as well. If you haven't I recommend you do. If you are getting proper fuel pressure then chance is coils or wires might need replacing. Do you get any CEL? To make sure your alternator is working properly get a multimeter and get measure while running the engine . The battery should put out 13-15 volts. Good luck

 

Yep, the fuel filter was changed, and the mechanic also checked to ensure no clogging of the remaining parts of the fuel line as well. And no CEL whatsoever so far. The fuel pressure was fine according to him after he had changed the fuel filter. The battery according to the mechanic is good; I don't know what output but assume is within acceptable range to the mechanic. I'll have to ask him if he checked the coil because he checked the plugs and said they are clean and in good conditions. Thanks for the comments.

 

And I also cleaned the MAF few months back with MAF spray cleaner. The MAF looked very clean then but I still cleaned it anyway. With current symptoms I just don't know if it will stall one day. I spent $600 so far and do not wish to spend randomly unless warranted. So I would greatly appreciate someone out there can shed some light on these issues.

 

Are they Bosch Platinum plugs? I've used them a few times, had nothing but problems. I've seen other people have problems with these as well on different forums. Just a thought?

 

Not Bosch, I used Hyundai recommended in owners manual - Champion RN10PYP4 made in Korea.

 

I also noticed the poor acceleration (hesitation, staggering, symptoms like stalling etc) in recent months whenever the stereo, air condition, fan on high, as well as another gadget like a bluetooth handfree kit plugged into the stereo and all running at the same time. The mechanic had checked the battery is good.

If it only happens when everything is on, then your best bet is it's something related to the electricity. I would check the alternator, serpentine belt etc.
If like you say everything checks out according to your mechanic, then that non starting has two culprits: either starter motor or the solenoid itself. I don't think it's a faulty sensor, you would've had CEL. Have you hooked it up to read codes? If your mechanic cannot figure out the problem just find someone who can, because we can just give you ideas here. Good luck!

 

I've read, early versions of this engine had issues with the intake manifold cracking after awhile, & getting an air leak. With the engine running, spray some carb cleaner around the intake manifold, and see if the rpm changes.

 

Today the cause of poor acceleration and hesitation was found at last! One of the coil packs has a fine crack and electric arc was seen intermittently jumping across to the engine cover and cause the problem. So after $250 was spent on a new after market coil pack, no more poor acceleration and hesitation. Now will focus on the other issue - starting only after second crank. Thanks to all who shared their suggestions and ideas. I will keep it updated when the problem is found.

 

Wow! Glad you found it! Maybe this will cure the 2nd starting issue as well? Good Luck, Mike