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I have recently acquired a 04 SF 3.5. I have been trying to diagnose this issue for the past few weeks. It all started when the car stalled on day at a stop sign. Soon realized it still drove ok, was missing i could tell but at stop lights car wouldnt idle and stall. I pulled codes and got crank sensor, misfire cylinder 5, sensor for tach, pedal sensor, tps sensor. I started with swapping a used coil in for the misfire. Check engine light actually went off after this. Still was stalling at stops. I changed crank position sensor and the tach sensor, forgot the name. Still drove fine as long as i kept foot on gas at stops to prevent stalling, rpms would fluctuate, then drop to 0, stalling. Soon I took a 45 min. drive, and doing 60mph suddenly died. Would not restart. I gutted last cat before the muffler thinking cat clogged up, i read that there were 3 cats? I presume Im seeing them on the exhaust manifolds? After I gutted the 1 cat, she fired back up, feeling like engine was missing, but running and driving but still with issues. Now whats happening is the car will run good cold, it will idle in gear at stops and all. Once the engine is up to operating temp, car once again stalls at stops, but has new symptoms, if i let the car stall, as the rpms are dropping the oil light dimly starts to flicker. Once car has stalled, I try to restart and all dash lights dim as I try to turn engine over, engine turns VERY slowly, so slow that car will not restart. I wait 10 mins. amd car will turn over a little faster, but manages to start. I got battery tested and it checks out good. I realize as battery being tested that alternator plug not connected. I plug in alternator but still have same symptoms. I changed the coolant temp sensor as I had a similar situation with a previous car so thought i would try that. No change after coolant sensor. I get codes re ran, and only 2 codes i get are bank 1 lean, and TPS sensor. So TPS is last sensor i need, but i think i have something else going on as my symptoms show and with the bank 1 lean condition.
 

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Tps is probably your issue. I assume you have your own scanner. If not, OBD link are good and can be used with your phone
 

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Update, after tps changed and cats now hollowed, car starts and idles but has no power. No codes yet i have spare set of coils so I swapped them all out also no change. Once engine get to operating temp, car will no longer idle in gear, it will idle in park, but in gear Rpms drop then dies. Sometimes it will pop through intake or an occasional back fire. In park it will idle fine and rev all the way to redline no problem. Soon as put into gear gotta stay on gas to keep alive and gotta press pedal fully down to accelerate reasonably but very slowly, I can smash on the pedal up and down and pedal almost unresponsive if in gear. Also once warm and I turn car off and try to immediately restart, the starter turns VERY slow all dash lights dimming severely. Tried a different battery with same results. Wait like 2-3 mins and starter turns fast enough to start. No codes, what do I look at next
 

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TPS is not a fault part in 14 yr of dealer work... APS is common fault (people dont have access to proper Hyundai DTC text and assume TPS).. likely compounded your initial concern now..

Have we scan for DTC ?? What DTC in proper Pxxxx format did we find ??

Hollowed out cats,,, see 0420 and 0430 codes coming now, since buffer between ox sensors is missing now.

Linear Throttle update for PCM to bring to last version of software, but that wont cause what you describe
 

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You really need a decent scanner to watch the live data when it is running. The MAF could be the issue. I have seen them read way off and still not throw a code but wouldn't run or would run very badly. That would be an expensive guess though. I would want to see the MAF data before I changed that part. The popping and backfiring is an incomplete ignition or wrong timing issue. You could try the pedal sensor as sbr711 recommended. Maybe a used one as new they are also an expensive guess.
 

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maybe user sbr711 can help you better.
 

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Discussion Starter #8
Here is the update, after plugs wires coils, no Change . The rear plugs were solid black, the front plugs were normal tan color. So symptoms are this, erratic idle, you Can rev it up to redline no problem in park, but in gear car feels super weak, it will rev up to redline shift gears downshift no problem, but feels like only running on 3 cylinders or something. When motor up to operating temp, idle will drop so low and stall. When accelerating there is also backfire through the exhaust and occasionally thru the intake. Also when at operating temp, after car either stalls or is shut off, when you try to restart right away, all lights in car dash everything dim out as starter turns very slow, usually so slow it won't restart. Wait like 3 mins and she will turn over fast enough to start. Under hood has faint smell of electrical burning, no smoke though. Also when in park idling, idle will be up and down between 1200 rpm to 500 and usually only stalls in gear. I tried a known good battery, and when warm the starter will still turn very slow. Haven't drove it far enough to get a code yet. So is there possibly some kind of electrical connection or relay that might be bad bad ground? Where is the engine to chasis ground strap?
 

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Here is the update, after plugs wires coils, no Change . The rear plugs were solid black, the front plugs were normal tan color. So symptoms are this, erratic idle, you Can rev it up to redline no problem in park, but in gear car feels super weak, it will rev up to redline shift gears downshift no problem, but feels like only running on 3 cylinders or something. When motor up to operating temp, idle will drop so low and stall. When accelerating there is also backfire through the exhaust and occasionally thru the intake. Also when at operating temp, after car either stalls or is shut off, when you try to restart right away, all lights in car dash everything dim out as starter turns very slow, usually so slow it won't restart. Wait like 3 mins and she will turn over fast enough to start. Under hood has faint smell of electrical burning, no smoke though. Also when in park idling, idle will be up and down between 1200 rpm to 500 and usually only stalls in gear. I tried a known good battery, and when warm the starter will still turn very slow. Haven't drove it far enough to get a code yet. So is there possibly some kind of electrical connection or relay that might be bad bad ground? Where is the engine to chasis ground strap?
Ah, yes. Ground. Hyundais have poor grounding systems.

Look for a braided "strap" that should be attached to one of the shock towers. If it's not there, it should be. Also check the battery ground. Hyundai expects a few threads on a bolt to supply enough grounding to support the electrical system.

Electricity will always try to find a ground, and if it is lacking a direct ground it will ground itself through something else. I wonder if those black plugs were black because everything was trying to ground through them?

Try attaching an 8 gauge wire to the block, and a suitable grounding point and see what happens. You can get the wire at a car stereo store that installs megasystems. if you ask them nicely they may even put good lugs on it for you.

PS: also follow the negative battery cable and see where it grounds to. It may be under the battery box.
 

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Discussion Starter #10
Ok ground strap was corroded replaced that and still no change. Battery went low during test drive. Car has no power is backfiring won't idle and max speed I can go is 45mph. Took battery out got tested was good battery just needs charging. Will charge battery and get alternator tested tomorrow.my theory is car is running off battery and therefore not giving car the full voltage needed to run. Il update after I get alternator tested
 

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Discussion Starter #12
Ground under battery box was corroded badly, ran new wire from battery to junction. Will check that interior ground in morning. Also another weird symptom it's having is, as the car is running badly, brake pedal gets hard , I drive a bit and it goes back to normal. I pulled booster vac line and plugged at intake but made no difference in way vehicle ran.
 

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Discussion Starter #13
Alternator putting out consistent 14 volts, battery good tested all multiple times. Had battery pulled out overnight and charged and fired up and drove normal for 1 min full power everything, then I felt it cut back to half power or something again only 45mph. After running ten mins battery feeling weak again???
 

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Discussion Starter #14
retested volts at battery while running real bad popping and what not and only getting 12 volts. At 2500 rpm
 

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I'm thinking alternator but I'm not getting a battery light when running. I tested if bat light comes on and it does when key all way forward motor off. There was instance where the battery light wasn't turning on with key all way forward. I stated up engine then turned off and retested for battery light and it was working again with key forward.
 

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May be difficult but I would double check the bank one plug wiring to be sure they are on the right plugs. Even if you one for one'd with the wire replacement I would double check them. Mix them up and this is exactly what it would do.
 

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Another question: after you picked up this Santa Fe, did it run OK for an amount of time? Or has it has issues since you got it?

If it was my car, I would first address the ignition issue. The beauty of the 3.5 is you can check those back plugs easily without removing much. An ignition test light would help. Those black plugs I would be concerned with. The rears not matching fronts is a classic lazy tune up because someone didn't want to remove intake. You can just pull off the plug wires and let them arc to ground. Keep your hands off them while doing this. You will hear and see the arc. Once you've confirmed they all fire nice and steady with no misses, then you know the plugs, wires and coils are all firing correctly. At least as commanded. It does not prove the the firing is in the correct order. IE: timing belt jump or broken teeth or other related ignition sensor.

You really have allot of issues going on and need a good scanner to help eliminate some things like the MAF. Some of your symptoms sounds like a MAF going bad. The popping and backfiring are a different issue (ignition)that could result in all of what you are experiencing.
 
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