Help;;; V8 code PO171

[firemech]

I have the 3.9 in a 2002 LS. Engine started running rough. Checked codes and found only a 171 code. Have been researching on here and see simular code with v6 engine. But different animal than mine. After running engine for short period, the exaust manifold on the drivers side is cold to the tough. Passenger side will burn you. Any suggestions on what could cause this code would be deeply appreciated.

[shorod]

Welcome to the forum!

As you're probably aware from your searching (thank you for using the search feature!) the P0171 indicates a lean condition on Bank 1 (the bank on the passenger side in US). According to the factory service manual, the possible causes for this code are:
For lean and rich DTCs:

• Fuel system
• Excessive fuel pressure.
• Leaking/contaminated fuel injectors.
• Leaking fuel pressure regulator.
• Low fuel pressure or running out of fuel.
• Vapor recovery system.
• Induction system:
  • Air leaks after the MAF.
  • Vacuum Leaks.
  • PCV system.
  • Improperly seated engine oil dipstick.
• EGR system:
  • Leaking gasket.
  • Stuck EGR valve.
  • Leaking diaphragm or EVR.
• Base Engine:
  • Oil overfill.
  • Cam timing.
  • Cylinder compression.
  • Exhaust leaks before or near the HO2Ss.

Since you are noticing a very hot exhaust manifold on the passenger side, I'd guess the code is accurate (very lean condition on that side). I'd start by checking for vacuum leaks. If you have access to a scan tool that can access the PIDs/CIDs/component parameters, you should check the individual cylinder misfire counts as well. You might have misfires that are not frequent enough to trigger a diagnostic code, but could indicate which cylinder may have a bad fuel injector. You could try moving the injector around, clearing the codes, then seeing if the misfires following the injector. Without such a scan tool, you could try unplugging one injector at a time to see which one doesn't make the engine run any worse, and that cylinder is likely the focus.

-Rod

[egddiesel]

My brother is having the same problem on is 2004 ls 3.9L, just wondering what you found as the problem on yours? I have checked for vacuum leaks, checked all coils, checked for voltage to injectors, disconnected injectors and the only ones that make it miss are on bank 1 (passenger side), I can disconnect all the coils on bank 2 and it doesn't run any rougher. Do you know where the schrader valve connection is to check the fuel PSI, I cant find it. But anyways just wondering what you found was the problem on yours.

[Aceliner]

Had a similar problem, Found oil on the coil pig tails, spark plug wells on bank 1 had oil in them. Changed Valve cover gaskets, changed all sparks and changed the coil spring/wires and boots, also had to replace the #2 coil due to the oil burning it out. Cost about 100$ plus my time all is well now though. 2000 Lincoln LS 3.9L

[badboy1]

I have a 2001 lincoln ls v8 3.9. My car stopped on me and its not cranking up again to start. The two codes that popped up were p0171 and p0174. Can anyone help me out? I looked at all the blogs about the v6 but there are few on the v8. Please help me out dont know too much about cars. Dont have money to change everything thing that could possibly be the problem. Need to know what to check out first whether it should be vacuum leak or spark plugs.

[shorod]

You mention "not cranking up again to start." Do you mean the engine won't spin over when you turn the key to start, or do you mean that the engine cranks but does not fire/start and run?

Was the engine running fine before this or did it idle roughly or stumble under acceleration and load? Luckily on the V8 the spark plugs are pretty easy to pull, you might start there. Be sure to inspect the coils for signs of oil or moisture while you're removing them.

-Rod

[LSLaing]

I have a 2000 LS V8 170K searched many posts here but seems to fit here best.
The LS has been running great then almost stalled when I stopped after getting off the highway has CEL- P0171 and P0175, replaced Fuel filter, Cleaned MAF, coils are dry (replaced gasket 2yrs ago), does not seem to have Vacuum leak, checked Compression all ~ 200lbs, took it to dealership (I know pretty foolish) they had fuel system cleaned and then thought it was the timing chain and wanted another $250 to look inside valve covers. Took it to another mechanic he found plugs were gapped wrong - reset to 0.44 and found misfire on cyl 7 & 8 with freeze frame scan, the fuel injectors were giving very little gas but firing, replaced injectors on 7 & 8. The car is still running rough at idle but on the highway Smoooth. $500 poorer and still wondering what is wrong... Catalytic, IAC, Timing????

[shorod]

Welcome to the forum!

Were the codes really P0171 and P0175, or was it maybe P0174? The codes you listed would suggest lean on bank 1 and rich on bank 2. It would be unusual to have a misfire on cylinders 7 and 8 due to too little fuel but still be showing a rich code. The P0171 (and a P0174) could easily be due to a vacuum leak which would explain your symptoms.

You might also check the age of your battery. If it's getting near 5 years old you might change it out before spending too much more time and money on the car. The electrical systems in these cars are notorious for sensitivity to old batteries.

-Rod

[LSLaing]

Thanks, I have been reading posts on this site for a while.
yes, it was a P0175... go figure. it has a P0307 (misfire #7) now. I read a post on another site where the Tensioner guide broke and caused the timing gear on the exhaust to jump a tooth. I have heard the battery thing before so i will swap with my other car and see if it changes.

[LSLaing]

Took the valve covers off and the Exhaust Cam had slipped a tooth, the tensioner is still in good shape and chain seems to be tight, not as tight as the other side so i am not sure what the root cause for the jump