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!