2005 Hyundai Tucson 2.7L - Random acceleration issues and hesitation
2005 Hyundai Tucson 2.7L - Random acceleration issues and hesitation
This thing has been driving us nuts! We're slowly but systematically replacing basically every relevant part suggested by the various codes it's thrown over the past few years, but it still acts up, totally randomly.
So far, we've replaced all the plugs, plug wires, coil packs, fuel pump, and crankshaft position sensor. I also briefly replaced the throttle position sensor, to which I didn't notice any difference either, but my roommate (the owner) thought that seemed to somehow make it worse so he had me put the old one back in. We do still have the new one though, and after what it did yesterday, I might put the new one back in soon. More on what it did yesterday a little later.
Still on the menu of other parts to check/replace are the mass airflow sensor, oxygen sensor, EGR valve, and camshaft position sensor (this model does have that sensor right?)
Anyways, what it did yesterday threw us both for a loop. While parked at the gas station and idling, he pressed the accelerator pedal, and literally nothing happened, engine RPM didn't change a single bit, even when he put the pedal to the floor it simply stayed at idle.
I wondered what the hell the computer was even thinking at that moment, like did the ECM just totally glitch out then or what? So I had him shut it down, wait about 20 seconds or so, and crank it back up. And sure enough it started responding to the accelerator again, as it has been for the past few years anyways.
I'm sure that it's at least partly related to the emissions control system, as the exhaust definitely smells like it's not burning all the gas (note that there's thankfully no visible emissions, just a notable odor), but why the hell would there be a random one-off where the vehicle wouldn't even respond to the accelerator at all until shutting it down and restarting it?
We'd go ahead and jump all in and replace all the other parts I mentioned, but ya know .. $$$ .. so we're tackling things as he can afford them and as we narrow down and correct obvious issues such as a few cracked vacuum lines that I've already replaced now.
Anyways, if you've read this far, thanks for your attention to this issue. If anyone has any suggestions or advice to help us find the issue and save our sanity, we're all ears! And thanks in advance.
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At this point I'd check the harness and the ECU. I'm assuming this car has a electronic gas pedal (not familiar with Hyundai myself) but absolutely zero happening with a fully pressed pedal is most definitely an electrical fault, maybe even from the gas pedal itself.
That may indeed be possible. The car has to adapt the learned values to the new sensor. Not sure about your specific model, but you can reset these values by disconnecting the battery for a couple of minutes on a lot of cars of that era. It takes a few minutes of driving for the new values to be written.
Oh, and yes, every time I replace anything that would require the computer to adapt, I disconnect the battery for at least 10 minutes so it can readapt.
That's the damndest thing, the accelerator pedal is old school physical cable operated, there's no way in hell it wasn't at least opening the air intake flap. I mean sure the TPS is electronic, but that was the only time it's ever outright just not responded to the accelerator. Restarting the engine got that back working as it has been all along.
As mentioned, I have tried a new TPS, but that to me didn't seem to change anything, but the owner thought that might have somehow made it worse, so he had me swap that back to the old one. We do still have the new one put aside though.
Another thing I should mention is that the vehicle overall seems to have some other random ghost issues that come and go, like the electronic locks work when they want to, and half the time the left blinker doesn't want to work until you fiddle with the blinker arm a bit.
Under the hood, most of the electrical connectors on the wire harnesses are dryrotted and falling apart, barely holding together with just hopes, prayers and dumb luck, so I'm sure that ain't exactly a good thing either, but at the same time I make sure to check all the connectors that I can readily see and access every time I'm under the hood.
Sigh, it's almost like a haunted house, but on wheels..
Oh yeah, that's definitely a tough nut to crack.
There are cars that do have a physical cable to the intake to operate a electronic control there. I had a car just like this from the early 2000s. The cable operated a potentiometer that would in turn give a signal to an electric servo on the intake flap. So it was cable operated, but still electronically controlled. I'm just guessing, but maybe it's similar on this car?
I don't see how else it wouldn't have died from the gas pedal being pressed without the revs increasing.
If the wire harness is as bad as you say, the issue is most likely related. Maybe you have some wires touching inside the isolation or an intermittent fault somewhere you can't directly see. I'd start by tracing it from the ECU to the throttle. I wouldn't blame the blinker stalk on the same thing though, it's probably just worn out.