Check engine light and high revs/Hyundai Tucson

Hi everyone. I’m after any ideas on what may be the issue with my 2008 Hyundai Tucson. I have had a check engine light appear over the past few weeks and I had it looked at and the code said engine running too lean. It was looked over for any vacuum leaks but none were found. It revs quite high when started then drops but now can rev upto 2500 and then drop then rev continually in Park when started. It also used to kick over then die until I replaced the battery and it seemed to help. The first mechanic that couldn’t find any leaks sent me to another for more in-depth diagnosis and that guy said his had a car at his shop with the same thing for over a month and he charges $120 a hour. No thanks! I went to a further 2 mechanics and both only had the same idea as the first guy so I am really not sure!

Could it just be a faulty sensor or? I am clueless and being a young female, do not want to be ripped off based on my lack of knowledge. So if anyone’s had the same issue, what ended up being the problem? Much appreciated!

Do you have the actual code number?

It will be something like, P0 and then numbers.


Yeah they wrote it down for me

“P0171 system too lean”

Thanks :slight_smile:


Thanks so much!

High idle and lean is a classic air leak.
Maybe the first mechanic wasn’t looking in the right place.
I’d first pinch off or block the brake booster, take a close look at the PCV system,
check the IACV (idle air control valve), check the dipstick and tube, and the oil filler cap gasket.

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