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Hyundai Santa Fe Spark Plug Problem

followme21followme21 Posts: 11
edited August 2014 in Hyundai
So I have been trying to help out a friend with her 2004 4-Cylinder Hyundai Santa Fe. About 4 weeks ago it was running very poor. I changed the spark plugs and discovered that the number 4 cylinder plug had a closed gap. I put some additive down the cylinder to break up any carbon build-up and replaced all the plugs and it was running great. About 3 days ago it started running poor again. I pulled the plugs and sure enough the number 4 had a closed gap. I opened it back up reinstalled the plugs and it is running fine again. This makes no noise at all.. no knocking or anything, and it takes several weeks and several hundered miles for this to act up. Any thoughs on what is pushing the gap closed. I dont know much about Hyundai's. any help would be outstanding.


  • somedai1somedai1 Posts: 416
    is their something bridging the gap or is it actually closed? any other conditions exist on the plug? what brand/type plugs are you running? It could be a few things- mechanical failure, wrong type plug. also, try cleaning out carbon with a 3 step system instead of pouring directly into plug hole - i wouldn't keep reusing that same damaged plug. And what do the other plugs look like when you pull this one and find it bad?
  • Thanks for the response and tips. I only reused this plug this one time so my friend could get home..a couple of miles away. I think the were "champion" plugs..and they are the ones the part house gave me for this application. The other three look great,good clean and a little white. This one was of course was black from incomplete combustion. And the gap is actually closed at the very tip of the electrode. What type of "mechanical failure" could cause this. And could you recommend a 3-step cleaning system? No other systems occur,... one minute is running great then all of a sudden a miss.
    Thanks again any help would be great.
  • somedai1somedai1 Posts: 416
    is the plug black and oily? or black and caked with soot? did you say no other codes from scanner except misfire? i guess detonation could cause the plug to get like that... just need to find out what caused the detonation... try changing the plugs to NGK - champion was not meant for Hyundai's - sometimes it doesn't matter but certain cars are particular to the type of plug... the other plugs seem to be running too hot... so they are white... maybe the plugs are hot plugs and you need to run a colder plug. also - this car is distributor cap and rotor? or coil packs? it may be needing more than just plugs...
  • The plug was more sooty then oily, and it wasnt a complete miss, because I pulled the plug wire off with the engine running and it made a difference as the engine about died, so even when the gap is closed it is still firing a little, I assume because only the very tip of the plug is closed. I was getting the code P0430--"catalyst system below threshold bank two". The car has coil packs.. number 4 has the pack on it.
    Thanks again for any input.
  • somedai1somedai1 Posts: 416
    hmmm. the catalyst below threshold could have been caused by the misfire... not the other way around... but one plug like that would seem like carbon build up or improper fuel mixture. either way - you should have more than one code... then again - it is a Hyundai... change the O2 sensor located after the cat and switch to NGK plugs...
  • I will try switching plugs.. and I'm with you, I am thinkng I'm getting that code-P0430 due to the incomplete combustion in that cylinder with the bad plug. But I will try the plug switch and see what happends.. Any other ideas I will listen to as well. If it was the plugs I would think it would do it to more then consistently one-cylinder. But worth a shot as I have no other clue.
  • somedai1somedai1 Posts: 416
    it could be the coil pack... if it is working intermittently- it could allow fuel into the combustion chamber that does not get burned... then when it does fire... BOOM- detonation- damaged plug- if the packs are interchangeable - switch it to another cylinder- see if the problem occurs again at the new position... try this 1st so you don't waste on the new plugs...
  • So I have done a little work. I replaced the plugs with NGK plugs and even replaced the coil pack on the number 4 cylinder..the plug that kept having the closed gap. Gave the car back to the owner she drove it for about 100 miles or so then it goes to missing again and I pulled the number 4 plug it was fine.. Pulled number 3 and now it had the smashed shut gap. I replaced it, went for a drive and it worked great.....I am gonna try soaking some sea-foam or A.T.F. in the cylinder to maybe break up and carbon build up thats floating around. Other then that I am out of ideas.. Any thoughts?
  • somedai1somedai1 Posts: 416
    I don't think carbon build up would close the gap tho'. any new codes? Timing may be off. I think too much fuel in the chamber would cause the plug damage. So many things could cause that but you would most likely get codes... Is that a timing belt car? was that ever replaced? how many miles on that car? but still... without other codes - you may want to investigate further into the O2 sensor issue - may be bad cat or sensor or both... clogged cat possible too.... try Berryman 3 step fuel system cleaner. Runrite or Justice Brothers could work but only the pros can get that stuff...
  • The only codes this time was the o2 sensor again, and then this time there was a cylinder 3 misfire.
  • somedai1somedai1 Posts: 416
    i guess the bank 2 sensor could be reading too little fuel and telling the computer to send more fuel and cause too much to be in the cylinder causing detonation/misfire... that has to be next step - O2 sensor...
  • I can try that, but if I had a camera here and could post a pic you would see that the side electrod (ground) is actually pushed up and off to the side of the center electrode. I dont know if pressure from detonantion could cause looks like something pushed it there. Esp when the O2 sensor is $105.00.....
  • somedai1somedai1 Posts: 416
    I don't think something mechanical like a cylinder hitting it is doing that damage. If it were mechanical it shouldn't happen at alternating cylinders. It is most likely detonation. and the fact that you're not getting any other codes is troubling. most cars don't get driveability problems when O2 sensors go - but Hyundai does according to the dealer. check this too - when you poured the stuff into the cylinder to break up carbon - how long did you let it seep in or soak? did you attempt to start it before installing the plugs to clear the combustion chanber of any remaining fluid? it is also possible that if the engine has so much carbon built up there is debris in the combustion chamber - blow out with compressed air.... lastly - which picture describes your plug - hooting/index.html
  • The second one up from the bottom.. the one that says "electrode is bent and insulator is broken" exactly what mine looks like...."causes being spark plug reach is to long or foregin material in cylinder"... the spark plugs the parts house gave me are "NGK BPR5EY" with a "11" under those numbers.
    I let the ATF soak in for about a day or so then yes I cranked the engine over to remove the fluid before installing the plugs. I did not blow out the cylinder with compressed air last time but am going to this time..
  • somedai1somedai1 Posts: 416
    has this car ever run low on oil or overheated? does the exhaust have white or blue smoke?
  • Dont know really about running low on oil or overheated or anything, its not mine I am just working on it for a lady friend....I do not notice any smoke coming from the tailpipe except when one of the plugs goes closed... it does have 127,000 miles on it so it is getting up there...
  • somedai1somedai1 Posts: 416
    i guess process of elimination that is cost effective could work - but timing belt may need to be done if it hasn't already. clean it, crank it, blow it out, crank it an blow again - install plugs an see what happens... O2 sensor costs less than timing belt...
  • 2003 v6 with 105,000 miles running rough at idle. figured it was a misfire & it was on 2, 4, 6 (the back 3) full diagnostic was done at the shop & replaced the wires & plugs. It's still running rough on 1, 3, 5 the hour after the plugs & wires are done. just spent $300 on that service. Any ideas on what would cause this jumping of misfire from side to side?
  • somedai1somedai1 Posts: 416
    does that car have coil packs or distributor cap + rotor? my 1st guess would be fuel injector problem or cap+rotor issues... misfire due to plugs usually doesn't occur on so many bat once... did you have all plugs changed? what brand of plugs in the car?
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