Intermittent loss of power/electic - 2004 Hyundai Elantra
 

I’m having an issue with my 2004 Hyundai Elantra cutting off, and am out of ideas of what to check for next. Basically I have a very intermittent issue where the car seems to lose electrical power for a split second (or possibly total loss of gas – as in, it doesn’t seem to be misfiring, just seems to totally lose all power). If it happens when I first start the car up, the car will start up for a second and then cut off. It also happens randomly when driving at any speed, and when it happens while driving, it just goes out for a split second, and then cuts back on and I can keep driving, so the RPMs Rev up for a second as a result when it kicks back on, but then goes back to normal. But it is completely intermittent, as in, some days it will not do it at all on my 30-min drive to work. I even went a whole week without it happening. But this week it has come back. Some days it will do it 3 times, some days 20 times. Some days its hard to get my car started, because it keeps cutting off when I start it. But so far after I try around 5-10 times it will start up and keep going. Also, this may indicate nothing, but when it goes out for that split second, I can hear a click, or electrical sounding click coming from the dash/instrument panel area. Which is what makes it seem electrical in nature, but I could be wrong, could be a spark/gas thing.



This has been happening it seems no matter what the weather is outside (its been anywhere from the 20s to 60s here in the last few weeks) and it doesn’t seem to matter if the car is warmed up or not. Also, so far the check engine light has not come on, so it makes me think it might not be a sensor, since those will usually trigger the light when they start going bad. Also, when the car is running, it runs perfect. Idles perfect, drives perfect, no misfires, no hesitation, etc. The ONLY problem is it cutting out. Also, it doesn’t seem to matter if the fuel tank is full or half empty. I had read in one place that if the vapor recovery charcoal canister gets full of gas, it will vent liquid fuel instead of vapor, which can result in car cutting off or running rough, but this usually only happens when fuel tank is full. So I suppose it could be this, but I doubt it.

The car has 180k miles. Iridium plugs have 60k on them. Wires have 60k on them. Original fuel pump and fuel filter. I wouldn’t think it would be the filter since when it runs it runs perfect. I guess could possibly be the pump having an intermittent issue. Trying to avoid replacing that for now unless I knew it was the problem.



What I’ve done so far:

• I made sure the battery cables are tight and clean at the connection

• I checked as many grounds as I could find, they all seem good

• Alternator puts out a perfect amount of voltage

• I swapped the ECU main relay and fuse with another relay and fuse in the fuse box that were identical

• I swapped the Fuel Pump relay with an identical one in the box

• I replaced the Crankshaft position sensor

• I cleaned the Mass Airflow sensor (though it looked spotless)

• I looked around for any vacuum hoses that were disconnected. Didn’t find any

• I’ve tried resetting the ECU (unplug battery for a while) and I thought that fixed it at first, but then it came back a few days later. And now resetting ECU seems to have no effect.



Some possibilities of what it could be:

• Fuel pump intermittent issue?

• Camshaft position sensor?

• ECU problem?

• Catalytic convertor going bad?

• Some other sensor going bad?

• Possibly the vapor recovery charcoal canister is full of fuel as described above

• ignition coils – but I doubt it since you’d usually get a misfire/engine light when those go bad (from experience)

• Fuel pressure regulator – but I doubt it, based on the symptoms. Seems like I’d have other symptoms.



I’m not convinced of any of these above, and some of them I wouldn’t know how to check (like for a bad ECU). Does anyone have any suggestions of what you think it might be? Getting nervous driving 75mph on the interstate with someone behind me and the car cutting out. Luckily so far it doesn’t cut completely off when I’m up to speed with someone behind me!

When it cuts out do all your lights go out as well? Dash and headlights?

It happens so fast, its been hard for me to tell. But I want to say they dont go out, or it seems like I would have noticed it. Most of my driving has been in the daylight. So yeah, if they do go out, thats probably an indication of something electrical I assume. Leaning 75% towards that they dont go out. I'll try to pay close attention.

Does the radio cut out? If you don't go out at night, maybe rig up a shade that lets you see the lights during the daytime? Can you jiggle the keys in the ignition and make it cut out? Do you happen to have a heavy bunch of keys hanging from the ignition switch?



It bears mentioning that your old-ish plugs, wires, and fuel filter really should all be changed. The fuel filter especially could be dodgy and just barely flowing enough, with the occasional not-flowing-enough tripping you up.



How is your PCV valve?

Have you cleaned the throttle body and the idle air actuator?

Does the exhaust pop when it happens? https://www.youtube.com/watch?v=kd-ix36A_Tk

If you rap on the throttle position sensor, maybe give it a tug and a twist, does it change how the engine runs?

http://answers.edmunds.com/question-...rs-128283.aspx





Intermittent stuff like this can be tough. Good luck, and be sure to keep us posted.

Sounds like an intermittent open in the harness. With the engine running, start jiggling parts of the harness to see if you can make it happen. Pay close attention to the crank position sensor harness.

So i drove to work today and it cut out several times. Made sure I turned the radio up to see if it cuts out. It doesnt out at all when the car cuts out. I did notice that the check engine light comes on for a fraction of a second some of the times that the car cuts out. I have a code scanner and have checked it 4 or 5 times over the last few weeks and no codes have been thrown.



I also tried jiggling the keys a lot while driving, no effect. So if an ignition switch problem, cant be replicated by doing that.



I agree that the plugs should be changed, and I have a new set, just havn't installed yet. Though i dont think it would cause the issues I'm having. Also agree the fuel filter should be changed. I'll get around to that eventually when i have some extra time. Its a little difficult to get to so have put that one off.



But one thing you did mention that was an easy (or I thought) thing to do is replace the PCV valve. I had taken the valve cover off maybe 60k miles ago and cant remember if I replaced the PCV. I've had oil leaks ever since, which I dont know if was due to me not sealing it good or a bad PCV. So went to autozone on my way into work and brought some tools with me. This car has a screw-in type of PCV rather than one with a grommet. So when I started to unscrew it, the metal threaded sleeve/insert in the valve cover was turning with the PCV. So i stopped, not wanting to cause there to be a big hole in the head cover.



Found this. Doesnt look fun. Stories of having to just force it out and JB Weld back in. Ugh.

http://www.hyundai-forums.com/xd-200...-my-fault.html



I'll try tapping on the TPS sensor later today. I know I've tried pulling, tugging on most of the sensor connections, battery connections, etc in the car to try to replicate the issue, but so far havnt been able to. I really dont think its a bad connection, but could be a sensor going bad. Just weird I havnt gotten the Engine Light through all of this.

Dude, this sounds so damn f*cking familiar, I had to check to see if it was an old thread I wrote!!! I had this problem and nearly got rid of my tib it was so damn frustrating. Diagnosed it for over a year. Same problems as you except I had a Haltech wired in. It ended up being a cheap 13 dollar part. I bet it's your ignition switch! That what it was with mine. I had diagnosed it once before by giggling the keys and not getting it to cut out. 3 months later logic brought us back to the idea that something is cutting ignition and fuel. It was that damn ignition key switch!! It's a cheap part and an easy replacement. Literally diagnosed the problem for probably 100+ hours and it ended up being a 10 minute job. Try it!!! You have nothing to lose!!

Hey now that could be the issue. I noticed you said that yours didnt cut out when jiggling the keys, yet the switch was still faulty. I didnt think it was my switch either, since I couldnt get it to cut out no matter how hard or crazy i jiggled the keys. Its definitely worth trying to replace a $13 part to see if that fixes it. Will do that tonight and see what happens (of course might take me a few days to really know!)

Hit the PCV with a drop of penetrating oil and be super gentle with it, maybe?



The radio might still stay on because the power supply has a little capacitance in it, just enough to stay on. Just saying that might not tell you all the electronics are necessarily staying on, is all.

Yeah I may try some more effort at the PCV before giving up and forcing the metal sleeve and all out. It almost looks like there is locktite or some kind of thread seal on the threads, which would unbelievable if they did that. THough its not blue, its kinda white looking. Lets hope its just crud that has gotten on the threads.



I replaced the ignition switch last night, due to tibbytib's post. Went for a short 15 minute drive, and no cut outs. But only time will tell, since it could be days before it happens again if the switch wasnt it. I also tapped on the TPS, tugged on the wiring, and other wiring under the hood again. Couldnt replicate it.

So I replaced the Ignition Switch and that wasnt it. Thought it was since I drove a day without a hiccup, but by day 2 the problem came back.



As a next troubleshooting step, I have a Bluetooth ODB scanner and the "Torque" Android app, so i got the idea to plug it in and turn on logging and have it log a data file while I drove and experienced the cutout. It logs stuff like speed, rpm, voltage, sensor data, etc of the car every 1/10 of a second. So I started driving, and I noticed that when it cuts out, the Bluetooth ODB scanner loses connection and has to reconnect. So the logs arent helpful since the ODB scanner loses power when it happens. But the fact that the scanner loses power for that split second during the cutout is very good troubleshooting information I think! I think this means that the ECU itself is losing power, which is why the ODB scanner loses power, since the ODB connection is what powers the Bluetooth scanner. This tells me one of two things. Either the ECU itself has some type of issue, or it seems there is a bad connection to the ECU. I say this because I dont lose power anywhere else when this happens (radio, headlights, dash) and normally the bluetooth ODB scanner has power when plugged into the ECU even if the car is turned off with no keys in the ignition. In other words power is always going to the ECU, and power is always going to the ECU's ODB port. But when the cutout happens, it seems that power goes away for a half second. Bad ECU? Loose connection maybe? Wiggling the harness and any wires under the steering column doesnt replicate it. I will say that about a month or two before this started happening, the voltage regulator on my alternator went bad and was actually putting out too much voltage to the car. I got a check engine light and looked up the code online and it said something like "Voltage exceeded 17 volts for more than 3 seconds". So then i tested with my multimeter and it was 16.8 which is higher than the 13.5-14.5 range it should have been in. So I put in a new alternator and that fixed it. So one possibility I'm thinking is that the high voltage could have damaged something in the ECU, though I'm not really convinced of that. But still contemplating getting a used one off ebay just to see what happens.



So I think this must be an electrical issue and has to do with the ECU or power to the ECU. As i think I said in my first post, I've already tried swapping the ECU relays and fuses, so its not that. Any thoughts?

Inspect and/or replace battery to chassis ground and engine to chassis ground. Try to shake ECU gently while the car is running. Pull on and shake connections to fuse box under the hood while it's running.

For sure check the grounds especially if there is one for (and nearby) the computer. Have a good look at the connector on the computer also. Maybe a bit of corrosion got in there? Connect and disconnect the computer connection(s) a few times, maybe it's "just" a bad connection.*



I'd be tempted to swap the computer with a known-good one or at least a junkyard one, but it's not my parts money. The voices tell me to beware of a junkyard computer not starting because the key has the wrong interlock code but I don't know about your model in particular. Can the computer on a 2004 be opened? If so, maybe a peek inside would be in order. Maybe there's (e.g.) a capacitor in there on its last legs that could be visibly bad. It's common to see 16V rated caps in automotive stuff generally. It's possible it took a hit from your bad alternator.



*no-fun anecdote: I had a car that would intermittently die like the key had been turned off, but would restart right away with the key to the Start position. Then it started really running like sh*t. The ECM was in the engine bay, and the engine had been power washed. The cable harness connector to the computer was all a mess of conductive corrosion by-products. With that cleaned up, it ran like new again.

Damn! Thought the ignition switch was gonna work for ya. Still sounds similar to my problem. I'd check grounds like others have stated.

Last night I took the ECU out. It was a freakin pain to get to all the bolts that needed taken out. But I finally got it out and took the cover off. It looked spotless inside. Circuit board looked perfect, no leaking caps from what i could tell. The connection to the ECU also looked perfect. No corrosion, tight connection, wiggling everything had no effect. I also cleaned up the ground from the battery negative to chassis (sanded more paint off, etc). Though it looked just fine. Did the same for the ground from Engine to chassis. I put everything back together and test drove it. No change. As another test (running out of ideas), i swapped my battery out for the battery in our other vehicle. They're almost exactly the same size. The battery was 4 years old, so its probably gonna need replaced in the next year or so, but it has been working perfectly, starts find, holds a charge fine. THough like i said in an earlier post, apparently an alternator putting out too high voltage can fry a battery to where it kills it and battery acid leaking out. That never happened, but maybe by some chance it has done something weird internal to the battery like shorted some cells out. I have no idea, just running out of ideas so trying anything at this point. Havnt drove it enough yet to know if the battery swap has made a difference.

fingers crossed, intermittent faults are the worst.

The wierd thing is your entire ecm looses power. Thats proven when you cut out, the obd Bluetooth dongle has to reset and you have to reconnect to your phone/tablet, correct? Still sounds like you are either loosing power or ground to the ecm.