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Hello guys, I'm trying to diagnose my wife's 2009, and not having a lot of luck. Here's the story: she left to go fuel up, and then go to work Thursday morning. 1.5 miles after filling up, she was accelerating after a stop light when the car started changing engine speed (she could hear it rev, and the RPMs went to 4K), without any increased throttle input on her part. Then it started stumbling, and acting up, and couldn't accelerate. She pulled off the road and called me. I scanned it, and it had a P2195 and P0107 (O2 sensor signal stuck lean B1S1, and fuel trim B1). I cleared the codes, but it didn't have any impact. The car could not accelerate, and can only barely move, which my initial read was limp mode.

The car starts, and idles relatively ok. I've spoken with others, more proficient than myself, and they thought it might not be limp mode, but might just be not getting fuel. The fuel pump primes and turns off as it should, but I know that doesn't mean it it's delivering the proper fuel. I always kind of expected a weak or faulty fuel pump would start showing some signs or symptoms before it just fails, but perhaps that is not always true. If I can get time tomorrow, I was going to figure out a way to check fuel pressure (doesn't seem to have a valve to make things easy), and the fuel filter. I was going to look at the MAF, and see what my scanner can give me for live data. I did read that one guy said the APS (accelerator position sensor, which I presume is the same as a TPS) can cause issues similar to this.

I'm wondering what people think about a situation like this? Could it be bad gas? Could something be plugging a fuel line, or the filter be plugged? Could it be as simple as the B1S1 O2 sensor? I don't know much about Hyundai, or what these cars tend to have for issues. It just seems odd that it was running fine, then went into a seemingly Limp Mode, and has not recovered. I guess I'll know more tomorrow if I can find a way to tell if the pump is working.

Extra credit: The car has had an evap code prior, but it doesn't show now. I think it was P0444, but when I just googled that, it isn't exactly what I remember the code being before. She said that the car seems to suffered a drop in fuel economy starting around Fall - couple months ago. We live in Maine, it's winter here, and about 8 degrees out with stiff winds. If I think of anything else that may help, I'll edit.
 

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Getting ready to buy some Tannerite....

I was hoping for a slightly more helpful response. So, after a week of no luck, I finally started throwing a couple parts at it, making educated guesses. I changed the upstream O2 sensor, because it ohm'ed out bad, but that wasn't it (I didn't expect it to be anyway). I also picked up a used ECM from a junk yard, but it didn't end up being the right one - but I tried it anyway, still ran the same. I cleaned up the chassis grounds. I checked the MAF, TPS, OCV, air intake, throttle body, and fuel injectors all good. I'm going to return the ECM.

I'm still stumped on why it would occur so suddenly. Driving down the road fine - after a fuel up though - then 1.5 miles later, it hasn't been drive-able since. I'm starting to really lean towards a clogged fuel filter, because the pump runs, and is pumping fuel (about 5Oz. in 3 key turns/primes - but I haven't found a way to check pressure though, and I'm not buying a $190 proprietary adapter). But if it's plugged enough to not allow for any forward movement, how is it sending fuel into a jug so well? I bit the bullet and ordered a fuel pump assembly with everything included for a fair price. If it works, then it was much cheaper than buying adapters and fittings to get a pressure guage to work, only to find out I needed to replace the pump, AND way cheaper than getting the dealership to diagnose it I bet.
 
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