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2005 Jeep Wrangler - manual with 4.0L inline 6
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Discussion Starter · #1 ·
I've had a number of problems leading up to my current issue. The mini cats collapsed into the main cat so I replaced that chunk of the exhaust system (including the O2 sensors) and while I was doing that I noticed the the exhaust manifold was cracked so I replaced that too. When it was all put back together I had codes (P0171 and P0174). I took everything back apart and made sure I got the intake manifold aligned right but I still get the codes. I also replaced the MAP sensor and the TPS sensor and cleaned the IAC and throttle body. When I erase the codes they can take a while to come back or they can come back immediately and there doesn't seem to be a condition that triggers them.

Today I was on the freeway and needed to speed up so gave it some more gas it sped up a little and then it suddenly lost a lot of power and started decelerating. I probably dropped from 70 to 50 over the span o about a minute. I was running an OBD2 scanner at the time. All four O2 sensors dropped to almost zero when the power dropped. Did the power drop because I was getting bad readings or were the readings low because something else was wrong?

Any advice is greatly appreciated! I'm almost desperate enough to take my truck to a mechanic.
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So intermittent lean mixture, loss power and low voltage o2 sensors

Most likely fuel pump failing
Makes for lean codes and running lean makes for higher o2 in exhaust which drops o2 sensor voltage as voltage from sensor goes up as oxygen in exhaust falls

Check pressure on fuel rail

Also post should include year and engine in your wrangler


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2005 Jeep Wrangler - manual with 4.0L inline 6
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Discussion Starter · #4 ·
Sorry. Forgot to include model and year - 2005 Wrangler - manual with 4.0L inline six - 125,000 miles
For some reason my truck doesn't have a tap on the fuel rail to check fuel pressure. Any suggestions? Also, I replaced the fuel pump a while back. When the mini cats dumped into the main cat I thought the power loss issues were the fuel pump. It might be a piece of crap though - nothing would surprise me. I've had to replace the clutch safety switch twice in 15000 miles
 

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Check fuel trims via obd2 port if they are high pretty solid assumption that rail pressure is low

What brand fuel pump did you use?


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2005 Jeep Wrangler - manual with 4.0L inline 6
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Discussion Starter · #7 ·
Here are the fuel the fuel trim numbers from my drive to work this morning (which went very smoothly - no periods where the power dropped out). I don’t know what qualifies as high for fuel trim.

A75A1635-8853-479F-AAB6-0D6437DB72B8.png
 

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The fuel pump was a CarQuest part number M2316406. What would you recommend?
Most will recommend MOPAR as #1 choice, Delphi as #2 choice... if MOPAR not available.

For my 05 Rubicon... I was in a hurry, because my pump failed.
I went with Delphi from NAPA, because they had it in stock at the warehouse and I could get it the next morning.
I also like NAPA, because they never give me wrong or bad parts and I get extra 10% with my AAA card. It was $178 after discount.
Got me running better than ever and all my P0174 codes are gone!
 

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High long term trim is pcm increasing injector pulse duration in attempt to correct over lean most likely due to low rail pressure


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That very well could be caused by the PCM, 05-06 PCMs have problems with O2 sensors. Maybe Mark at @wranglerfix will have some good input, his company regularly fixes issues with the 05/06 Wrangler PCM.
 

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2005 Jeep Wrangler - manual with 4.0L inline 6
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Discussion Starter · #11 ·
Interesting. Do my trim numbers qualify as high? I’m not sure what’s normal. Is the PCM problem something that can start suddenly after changing O2 sensors or some of the other parts I’ve changed? Everything was fine until the cats fell out.
 

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The oxygen sensor issue with the PCI NGC computer used in 05-06 TJ and 04-05 PT cruiser and Turbo PT cruiser 05-06 is with codes for o2 sensor heater circuit voltage high or low not actual sensor output voltage issues

Normal long term trim is near zero as little variation is needed from internal fuel map



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2005 Jeep Wrangler - manual with 4.0L inline 6
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Discussion Starter · #13 ·
Thanks for clarifying that Digger. Is there a convenient way to read fuel pressure on a truck that doesn’t have a valve on the fuel rail?
 

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The shop manual uses an adapter with male and female ends inserted between the fuel line and the rail at the rail connector and that adapter has a short hose with a pressure port in the middle of the hose

They are available but pretty pricey

Some (including me) get a rail at junkyard with a pressure port off an WJ or XJ and swap that on

Rails need to be from 4.0 97 on when they only used one line (no return line and no regulator with vacuum port on front end of rail) basically no YJ or early pre 97 xj or zj

The rails come with and without small pressure damper and with and without pressure port with small cap

I prefer the no damper and with pressure port whenever doing a swap


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