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09-22-2019, 03:17 PM
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#1 |
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Registered User
Join Date: Nov 2009
Location: Belleville, Michigan
Posts: 32
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PO171 and PO174
I have a 2002 1500HD with a 6.0 with 133000 miles on it, a couple of days ago it started running really bad but no check engine light came on, I was able to drive it back home and hooked the scanner up and it through these 2 codes, I cleaned the MAS air flow sensor and replaced the air filter and it ran fine so I cleared the codes and drove it a few miles then it developed a slight hesitation off of idle, I have checked for vacuum leaks and have not found any, checked the fuel pressure and its only running 25 to 30 pounds with vacuum line unhooked at the regulator, I changed the regulator and it still reads the same, what should the fuel pressure be and is there a certain way your supposed to check it, thanks in advance,
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Rick  69 SWB Project 95 Suburban Daily Driver 47 Flxible Motor Home 427 GMC 4spd Allison 71 C-10 LWB 307/350 (parted out) 64 SWB Custom Cab 283 powerglide (sold) 2000 Yamaha Venture |
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09-22-2019, 05:28 PM
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#2 |
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State of Confusion!
  
Join Date: Jul 2002
Location: Gulfport, MS USA
Posts: 47,249
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Re: PO171 and PO174
Have you check for intake manifold leaks? I have also heard an exhaust leak before the first O2 sensor(s) can cause that lean condition issue.
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Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God! |
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09-22-2019, 07:12 PM
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#3 |
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Moderator
 
Join Date: Jun 2017
Location: Cherryville, NC
Posts: 2,204
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Re: PO171 and PO174
Key on, engine not running, fuel pressure should be 55-60 lbs
Turn key off and fuel pressure should not drop by more than 5lbs... 25 to 30 running is way too low....its a wonder it runs at all... Sounds like a bad fuel [pump or bad fuel pressure sensor....my money is on the fuel pump...
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Family and country before all others... 2006 Chevy Silverado (Daily Driver) 2012 Chevy Equinox 
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09-27-2019, 08:47 PM
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#4 |
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Registered User
Join Date: Nov 2009
Location: Belleville, Michigan
Posts: 32
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Re: PO171 and PO174
Ok I found out the fuel pressure tester I was using wasn't reading right, my pressure is 55 not running, I did change the fuel filter and it has been running great, thanks for the help.
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Rick 69 SWB Project 95 Suburban Daily Driver 47 Flxible Motor Home 427 GMC 4spd Allison 71 C-10 LWB 307/350 (parted out) 64 SWB Custom Cab 283 powerglide (sold) 2000 Yamaha Venture |
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10-26-2019, 09:38 PM
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#5 |
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Senior Member
Join Date: Sep 2005
Location: Lewisville, Nc
Posts: 10,238
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Re: PO171 and PO174
Mine did same thing turned out to be intake gaskets
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David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube |
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