2003 Hyundai XG350

2003 HYUNDAI XG350
86,651 MILES • 6 CYL • FWD • AUTOMATIC
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PEGE
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  • 1 POST
when driving usually for extended hr/hrs on interstate at
70 mph-then for no apparent reason cars stops accelerating and drops to 30-40 mph-no check engine light-started around 2005-got the first check engine light
Oct. 09-codes were PO171 and PO174. Have replaced mass air flow sensor, timing belt, sensor assy-thrott-used gas accord to manual then switched to highest rating.
Original owner, kept up reg maintenance
Nov 6, 2009 at 10:35 AM
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MERLIN2021
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  • 17,250 POSTS
These are mixture lean codes, so check the fuel pump pressure and check for vacuum leaks, stuck EGR.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
Nov 6, 2009 at 3:25 PM