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Discussion Starter #1 (Edited)
hi everyone and thankyou for any help you may have.

2003 santa fe base model 2.4l i4 standard transmission

Runs great sometimes and then other times it can stall or hesitates, misfires, or all three. Noticed its not so apparent over 2200rpms. No CEL. CEL works though. Seems to run a little better after engine warms up but not too much better. It still can stall, hesitate, or misfire at any temperature outside. Been battling this problem for a year now. Read many forums. Tried :

Crank sensor
cam sensor
spark plugs / wires/ boots
both ignition coils
fresh oil and filter (who knows, hoped it would help)
checked timing (was right on)
wiring harness "jiggle" tests
Maf sensor was replaced a couple years ago

I was thinking of going in to look at the fuel filter next
and I believe the cat is not clogged. believe that was changed also.

dealership said there are no updates for ecm/pcm
and recommended a carbon injection fuel line cleaning for injectors

I feel like its something more electronic though because of the fact that it can run great for 2 days and then like crap for the next 3.

Is there anything im missing? Any help is greatly appreciated.
 

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Has this car been checked out by an actual mechanic, or are you taking stabs in the dark as to what it is?

Generally speaking, if it's random, then you need to figure out what is the common denominator to the randomness...heat, moisture, cold, sits for a few days, driven every day...things like that.

If it's random, it's harder to figure out, but if you can pinpoint specific outside elements that may affect it ( hard turn, hard bump in the road ), it helps to determine what system is being affected.

Could be a loose connection under the hood ( have a friend with a Ford Explorer that was like this..ended up being the main engine wiring harness plug had worked itself loose due to a broken clip. Zip ties solved the problem.
 

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One question, does it ever stall when it's first driven, like within the first 1/2 mile? Or does it only do it when it's been driven for a while...that can eliminate or add a few things to the list of possibilities on the sensor side of things.
 

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"Is there anything im missing? Any help is greatly appreciated."

Check your fuel pressure regulator. It's the unit at the end of the fuel injector rail with a small vacuum line coming out one side and goes to the intake manifold. It's VERY simple....with the engine running, pull the vacuum hose off the regulator nipple and watch the nipple...if you see a drip of fuel come out your regulator is bad...the diaghram is leaking and causes three issues....incorrect fuel pressure, vacuum leak and raw unmetered fuel going directly into your engine past the throttle body. I fought this on my santa fe and found the solution on this forum....so I tell everyone about it. BTW, the regulator is around $35 on Amazon. Worth it to change even if it's not the problem because after a while it would need changed anyway.

P.S. - I also had done the oil, filter, spark plugs, wires, etc before I found it...and it doesn't trigger the CEL or a code so expensive garages and mechanics computers cannot help with this one....
 

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Discussion Starter #6
hey thanks! for the replies, I got some extra time so i'm going out there to try a few things, tps plug, and look at that fuel regulator as stated above.

I wasn't really ever taking stabs in the dark. I always try to read and read before I try anything. Use my symptoms and other peoples symptoms and fixes to hopefully send me in the right direction to fix my problem.

Hope to keep this thread going until fixed, so again, thankyou for all your time and brain power for the help.
 

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Discussion Starter #7 (Edited)
alright, I checked the fuel regulator vacuum port that goes in between that and the manifold, it looked the tiniest bit moist, smelled a little like gas, but the nipple points up and there is no way for gas to drip out. might need changed but I don't think that is the definite problem.

pulled off the tps harness connector, tried to rev it a few times and that's when it missed sputtered and died on me. wouldn't start back up.

waiting for it to cool back down a bit to try again.

when it does stall, I won't be able to start it for awhile, then when it sits you can drive it for a couple minutes before it dies again.

I did however notice that the exhaust manifold has 2 big cracks in it, cylinders 2 and 3, close to the exhaust to head flange right by the studs, and you can see wetness coming out from the cracks, maybe gas? maybe some oil too? when I rev it, smoke and wet stuff spits out of the cracks.

I suppose that if the exhaust gas is leaking before the o2 sensors that it would run a little rich or lean or throw a code, but not cause it to stall and not start....right?

also tried the egr test where you clamp the vacuum hose with the yellow stripe closed to see if the system is leaking. online said to clamp it and if the car runs rough and then stalls that the system is good. I clamped it and it ran rough but DID NOT stall. soooooo.....that means my egr system is leaking too?

also realized the tach goes to 0 like a millisecond before it stalls out completely.
 

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Sputtering , hesitation..

Try this before you take it for a drive the next time..

Get yourself a good heat gun, and make both coils hot
I mean really hot , this should drive moisture out of them.

Let me know If that makes a difference..

Re Exhaust Manifold..

Mine had a crack as well...

never knew it was there, until I removed the bolts holding the shield down, as preventetive, I wanted to replace them with stainless steel

Shield has since returned to earth as rust.

Mine an 02 2.4 had the manifold replaced under warrenty in 06 1000$ part.
 

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I'd go in to look at the fuel filter. Even just to clean it. Mine was 90% blocked (02 2.4). Caused the same symptoms after driving a while. ("runs rough after 1 hour" thread.

Costs nothing to have a look.

Rob
 

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Discussion Starter #12
i got the pump out and when talking about checking the fuel filter are we talking about the foot screen on the bottom or the black filter that encases the fuel pump in it? The tank inside looks clean, the foot screen looks brand new, but how do i check the black circular filter?
 

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Ah, I missed that, If both coils have been replaced, then chances are your not having troubles there

I can't help you with the filters, and or screens...

And would be afraid to take the top opening off my tank again fearing a total colapse of rust

whacker
 

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Discussion Starter #14
i blew through the black filter that the pump goes in and all kinds of black colored sooty gas came out, a little hard to blow through, gonna just change it, to be sure. one thing i noticed was there was no o-ring in between the foot filter and the pump inlet. is there supposed to be one?
 

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Discussion Starter #16
changed fuel filter, like I said was clogged some, but definitely not the problem. still same problems. but now Im pretty sure the ecu isn't getting the crank signal intermittently. Got the crank sensor circuit code now. Im gonna check for crank pulse signal at the ecu and make sure. but yeah, only when it wont fire up.

After checking the crank sensor and it shows good, Im probably just gonna run 3 new wires from ecu to crank sensor connector.

I suppose ill be chasing some electrical problem down for a minute.
 

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Discussion Starter #17
so, when it stalled, I checked the crank sensor output and inputs, all readings where fine.......but, well I was messing around in the engine bay with the key on run, engine off, I heard some twitching coming from the ecu relay in the fuse/relay junction box. think its called the ipdm. and when it twitched, I could hear the fuel pump kick on and other systems turning on and off. tested the relay and it has a bad diode. turns out the relay is special order from everywhere (29.00$). don't know if this is part of my whole problem but we'll see.

read that the ipdm has an actual circuit board in it too that could be causing problems.

realized that once it stalls and won't start that there is no spark and the fuel injectors don't cycle. fuel pump still runs while trying to start it.
 

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I'd replace that relay. Sounds like you've got a bad coil in it or a bad contact..they do go out from time to time.

Beyond that, the vacuum side of the fuel pressure regulator should always be dry. There is a vacuum being applied to that port, so moisture won't go to it, but if it's being drawn by vacuum, then you may have a pinhole leak in the diaphragm that is allowing traces of fuel to be sucked into the vacuum line. This will eventually cause other problems as fuel gets sucked through the vacuum system and the gasoline starts to break down the plastic lines/connections.
 

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Discussion Starter #19
Got a new relay for ecu relay in hood fuse/relay box, put it in, didn't click on at all now. could it be bad straight from manufacturer?

well, now I was told there is a separate computer board (ipdm) with another ecm relay inside the fuse/relay junction box, idk, guess im gonna open that up and have a look.
 

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Discussion Starter #20
I just jumped the ecm relay and it still stalled last week, I still have no codes thrown, but I read the ignition failure sensor can make the ecm turn off ignition and wont let car start.

gonna test that I guess
 
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