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
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
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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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