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Discussion Starter · #1 · (Edited)
:confused: Recently replaced plugs/wires on soon-to-be 10 year old '04 SF 3.5L (157K mi.) for the first time. After reading all available posts and many hours of work, not to mention moderate loss of flesh and slightly less than fatal loss of blood, job was finished.
Plugs were OE Champion Platinum and all 6 looked identical except for excessive gap of .010 +/- due to all the miles. Replaced plugs with same as OE. Old plug wires looked good, but replaced them with aftermarket wires ( fit was as good as OE). Also replaced
plenum gasket.
Problem is: engine runs rough at idle and high rpm and appears to be mis-firing. CEL is off and code reader shows no Trouble Codes stored.
Would appreciate any ideas on diagnosing/correcting problem.
 

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Discussion Starter · #3 ·
All electrical in place. Can locate no vacuum leak. Wouldn't OBD indicate
trouble codes if these two possibilities were present??
 

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All electrical in place. Can locate no vacuum leak. Wouldn't OBD indicate
trouble codes if these two possibilities were present??
Make sure EGR is secure. Did ya lose the little silver gasket? Very common to drop those and not know it. If it hasn't set a code, it will soon.
 

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ok. a way to detect a vacuum leak . with the car in idle, spray some wd-40 or starting spray around the plenum gasket and areas you worked on. if you notice a sudden change in idle, you found your leak.
 

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After doing the plugs on my Kia Sedona (almost the same motor), my car too ran rough at idle and funky at speed. I changed out the plugs a few more times, and changed the gasket too... no help.

Finally after MONTHS of looking at it, I discovered the TPS was loose and adjustable and had come out of whack when I slid the manifold out of the way to change plugs. I put the TPS back to where I thought it should go and tightened it down, now it runs terrific... problem solved.

TPS is a little hard to see, and the screws are turned around to the firewall. You almost have to remove the throttle body to do it right. I was able to Scottish engineer a little screwdriver tool to tighten it as is.

See TPS pic on eBay:

Auto 7 037 0009 Throttle Position Sensor | eBay
 

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Discussion Starter · #8 ·
MikDee - Wires are from Import Direct out of Springfield, MO. Carton states
"....sets are designed to meet or exceed OE requirement". Purchased from
O'reilly Auto Parts, also based in Springfield.
 

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Discussion Starter · #9 · (Edited)
Rough Engine - '04 Santa Fe 3.5L

Make sure EGR is secure. Did ya lose the little silver gasket? Very common to drop those and not know it. If it hasn't set a code, it will soon.
Carmine: If there was a little silver gasket, I surely did not observe it. I saw no evidence that a gasket had ever been installed. Both mating surfaces were slightly discolored (brown), certainly due to exhaust gases, but there was no visible clue on either surface to indicate a gasket had been installed. In addition, EGR System Monitor shows "EGR OK". If a gasket is required here, that may very well be my problem. Thanks!!
 

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MikDee - Wires are from Import Direct out of Springfield, MO. Carton states
"....sets are designed to meet or exceed OE requirement". Purchased from
O'reilly Auto Parts, also based in Springfield.
Sounds reputable enough! Are the original spark plugs resistor type, is there an "R" in the numbering? If so, you must replace with the same type, or there might be a problem.
 

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check that the air intake hose is secure in place with no leaks. do you have fuel trims numbers? stft and ltft? make sure the spark plug wires are in their correct position. check that the tps is connected and working properly.
 

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fuel trims are the adjustments the ecu does for the fuel injectors. can be read from some scanners . if you can get voltage from the o2 sensors, you might be able to get the fuel trims too. the value is given in + or - percent (%) example: -3%, or , 5%... negative numbers means the ecu is detecting a a rich condition and is cutting some fuel. positive number means it is detecting a lean condition and it is sending more fuel to the combustion chambers. it is common that when you have a vacuum leak, the ecu will try to compensate by sending more fuel, so you might get a higher than normal short term fuel trim number (example, 12%). short term fuel trim is what happens at that moment. long term fuel trims are kind of an average of the short term fuel trim. used when the engine is cold, running in open loop). those values are only examples. also, if you removed the maf sensor, make sure you installed it with the arrow pointing towards the throttle body.
 

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Discussion Starter · #15 · (Edited)
Juanky - Thanks for the education. My code reader is apparently not sophisticated enough to read these trims as manual makes no reference to them. Did not remove the maf sensor.
 

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ok. but you removed a couple of things just to accomplish the job. make sure the spark plug cables are in their correct place. pcv valve connected, all electrical cables connected. no vacuum leaks. i heard that there is some kind of electrical motor in the intake area that might need ¨a reset", but i dont know. just think, ¨what did i touch, removed, pushed to the side, etc¨ and look. get some carb cleaner and start the engine, spray that thing around the areas you worked and if you notice a change in the idle you can tell there is a leak. did you replace the plenum gasket? stuff like that...
 

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Discussion Starter · #17 ·
Juanky - just to let you know - triple checked all items you listed and did
the carb cleaner thing; no change! Beginning to think I may have some
badly contaminated fuel. Thanks again.
 

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forgot to tell you to check the tps. we still have a trick we can try. before you start removing the fuel tank or the fuel from the tank you can try this. if you have a bug spray can, the type you pressurize with a handle (you can buy one at home depot for around $20), fill it with some fresh gasoline and connect a hose from the sprayer to the fuel intake of the fuel rail. pressurize the pump and try to start the engine. if it runs better, then your problem is fuel delivery/bad fuel. if problem stays, it could be dirty injectors. you can then put injector cleaner into the sprayer and clean the injectors. if problem goes away, you are done. if problem stays, then we need to start thinking or wait for somebody with more experience to help us, or start looking somewhere else....
 

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forgot to tell you to remove the fuel pump relay if you are going to try the bug sprayer thing. that would be a good time to check your fuel pump pressure and fuel pressure regulator
 

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Discussion Starter · #20 ·
To All Interested - Final Chapter, this edition: removed intake tube, checked MAF and Carb. bore for cleanliness. Both clean. Re-assembled and added can of injector cleaner/fuel conditioner to est. 15 gallons of fuel remaining in tank. Took out today and drove 25 miles at low and hwy speed. No missing, No CEL, no codes. Total cost (not including my labor) for Platinum plugs, plug wires, gaskets and fuel additive: $85.00
Thanks to all members who provided input, very much appreciated.
 
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