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P0171, P0174

Tiny
MACK2448
  • MEMBER
  • CHEVROLET SILVERADO
I have a 2002 Chevrolet Silverado with the 5.3 engine. It has 106,000 miles. Last winter my service engine soon light was displaying 0171 and 0174. Fuel pressure was in specs. I replaced MAF, IAT, air filter and could find no vacuum leaks. Problem still there. I replaced fuel filter twice. No good. On cold mornings the truck would idle rough for 8-10 minutes then smooth out. No one could tell me anything else so I resorted to driving it and resetting the SES light every few days. After the weather warmed up in spring I have had no light all Summer. It has been 30 degrees for 2 days now and my light is back on with 0171 and 0174 showing. Fuel pressure tested right and I bought the MAF cleaner recommended by my parts store clerk but nothing changed. The truck runs fine after it warms up. Any help is appreciated. THANKS
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Wednesday, October 31st, 2007 AT 5:56 PM

4 Replies

Tiny
SERVICE WRITER
  • MECHANIC
  • 9,123 POSTS
The 5.3 had a problem with leaking fuel pressure regulators is one thought, typically you would smell some raw fuel.

A leaking intake is the next thing I would question, spray some carb cleaner around the intake and look for a change in the rpm. This has to be done when it is cold as the contraction of the metals are at their greatest.
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Wednesday, October 31st, 2007 AT 6:28 PM
Tiny
MACK2448
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I traded pressure regulators with a friend, mine would still trigger codes, his still hasn't. I sprayed starting fluid around the entire engine compartment with no change but I don't think the engine was cold. I will try that next. Thanks for the help, Mack
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Wednesday, October 31st, 2007 AT 9:12 PM
Tiny
SERVICE WRITER
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'd be careful using starting fluid, that's pretty volitile.

Start with going around the intake and plenum gaskets first that is the most common place on these that I have seen.

Troubleshooting is knid of funny, if the problem isn't there, you can really spin your wheels. The COLD gives away the secret on this one.
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Thursday, November 1st, 2007 AT 5:30 AM
Tiny
DENNYP
  • MECHANIC
  • 1,823 POSTS
THE P0171 & P0174 CODES ARE A LEAN FUEL MIX CONCERN. THIS WOULD BE CAUSED FROM THE INTAKE GASKETS LEAKING WHEN THE ENGINE IS COLD.
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Friday, November 2nd, 2007 AT 7:01 PM

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