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PO171 Head scratcher

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Old 08 Jul 2016, 03:27 am
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Join Date: Jan 2011
Location: Arizona
Posts: 41
Default PO171 Head scratcher

2004 PT Cruiser NA 156,000 miles
No major work done lately other than oil change and coolant exchange
Timing belt was done at 100,000
I have an Autel Autolink Al539 ODB II and electrical scan tool that reports the code P0171 bank 1 lean.

Here are the issues:
  • The car takes two to three attempts of cranking before it will start
  • The car bogs down if the accelerator is pressed hard can only be driven if the throttle is feathered
    • There is a loud sucking of air sound coming from the cold air intake when the car stumbles or hesitates. I have a AirRaid CAI that has been installed and working fine for 10 years.

    Troubleshooting I've done:
  • I've replaced the plugs and wires. I found that some of the gaps had increased to .50+. New plugs are Champion platinum and gapped at .40. There was some improvement in idle but remains hard to start and throttle hesitates and or bogs down to the point of the engine stalling.
    • I replaced the MAP sensor and there was some improvement but main issues are still there, hard start and throttle hesitation or bogging down.
    • I replaced the PVC valve. I found that if I disconnect the PVC hose the idle raises to 2000-3000 RPM and the engine runs strong with no hesitation.
  • I replaced the O2 sensor closest to the engine and noticed no change.
  • I sprayed carb cleaner on all of the vacuum hoses and intake but did not notice a change in idle.

As it stands all original parts have been reinstalled with the exception of the spark plugs and wires. I don't think fuel is an issue because the engine runs strong when I disconnect the PVC hose. Thank you in advance for any ideas you have on what I should try next.

Last edited by jjackson23; 08 Jul 2016 at 08:36 am.
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Old 08 Jul 2016, 06:36 am
LionPT's Avatar
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Join Date: May 2014
Location: Central Florida
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Default Re: PO171 Head scratcher

Spray around the intake might have a gasket problem from when you replaced the plugs.

2006 Touring Edition in Cool Vanilla...aka/Ghost
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Old 08 Jul 2016, 09:29 am
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Default Re: PO171 Head scratcher

This code can be caused by low fuel pressure, bad oxygen sensors, vacuum or air leak, or incorrect valve timing.

I would suggest checking the fuel pressure. Make sure you are getting 58 +/- 5 PSI.
If at First You Don't Succeed - Try, Try Again
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Old 08 Jul 2016, 07:31 pm
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Join Date: Jan 2011
Location: Arizona
Posts: 41
Default Re: PO171 Head scratcher

Bingo! I've never used a fuel pressure tester before but only saw 19 PSI when testing via the Schrader valve. I watched an AutoZone video so I think I ran the test procedure correctly. I'm a DIY guy but working with gas makes me nervous so going to have to find a mechanic to replace it. I appreciate the help and learned something new today.
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