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  #1  
Old 10-24-2014, 10:24 AM
Andy9er Andy9er is offline
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Question PLEASE HELP!!! System Too Lean P0171 - Erratic Idle, Check Engine Light

My truck I just bought is now having this issue...

After changing the spark plugs after I bought it, I found oil sitting in the 2 middle cylinders where the spark plugs mount (Cylinders 2 & 3). I drained it (turkey baster pump) & installed the new (Ford Motorcraft Dbl Plat) spark plugs.

I gapped them to the number provided under the hood (1.25mm - 1.35mm). I started her up & no problems...but I took her for a drive on the freeway & down the street & once getting off the freeway exit & stopping at the light, the idle began dropping then rising (but staying under 1K rpm). Eventually the engine stalled. I pulled in to a gas station, waited, started her back up & eventually made it back home.

So now, after doing research myself I have learned the following BUT STILL HAVE THE PROBLEM:

Check Engine Light came on (& when its on, the idle problem seems fine). I learned that this is because at this point the engine has learned to compensate for what may be going on.

I have done the following:

- Ran DIAGNOSTICS & it gave me code p0171 & says "System running TOO LEAN"

- I have pulled off the IACV & sprayed it clean (wasn't really dirty anyway)

- Replaced Fuel Filter

- Checked all hoses (vacuum etc)

- Checked the spark plugs once again & the wires (I have a spark from all 4)

- Checked Air Filter & intake hose

- Checked throttle body & spring lever connecting to it

PLEASE HELP!!! Not sure what else to do or check!

Advice please: I was even thinking of adding a bit of oil in those 2 middle cylinders like it was before I changed the spark plugs to correct any vacuum/air leak that may be coming from the intake manifold gasket, at least to buy some time on replacing the gasket & correcting the potential vacuum/air leak.


PLEASE HELP!!! Any advice would help!!!
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Last edited by Andy9er; 10-24-2014 at 10:28 AM.
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  #2  
Old 10-24-2014, 10:46 AM
riscorpian riscorpian is offline
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Default Re: PLEASE HELP!!! System Too Lean P0171 - Erratic Idle, Check Engine Light

The oil leak on plugs 2 and 3 for the 2.3L…whoah, I didn't even think of that before. 2 and 3…2.3…? Interesting.

Oh, uhhh, right. That oil leak on the middle two spark plugs is probably the most common issue people have with that engine. It's likely just that your valve cover bolts have loosened a bit over time. Grab a wrench and snug 'em down a bit. There are two bolts in the center section, and they're what hold the part of the valve cover gasket that seal the spark plug tubes. Make sure they're snugged up, but do not overtighten them. They're very low torque, and I believe '04 was the year Fordzda switched to plastic valve covers. So yeah, be careful.

The P0171 almost always indicates some kind of vacuum leak. Let the engine idle a bit, and listen very carefully around it. You'll probably hear some kind of hissing sound. That's unregulated air getting in through something. Grab a can of carb cleaner, and spray around where you hear the hiss. If the idle changes all of a sudden, then you've found the leak.

Specific areas to look for (ordered by likeliness of the cause):
  • PCV valve & hose*
  • Intake manifold gaskets right up against the cylinder head
  • Throttle body gasket
  • IAC valve gasket
  • EGR tube gasket
  • EVAP purge canister hose(s)
  • A/C hoses
  • Brake booster hose

*The PCV valve is your most likely culprit. It's hidden underneath the intake manifold. Take the driver's side splash shield off of the inner fender, and look for the crankcase ventilator (the black thingy that's on the side of the engine). The valve is right on top of it, and it has a hose running up to the back of the manifold. First time I had a rough idle & P0171 code, that was the cause.

[EDIT:] You don't need to gap Motorcraft plugs. If they're the ones specific for your truck, they're pre-gapped already. Trying to gap them yourself could easily do more harm than good. It should say right on the box that the gap isn't adjustable, so you're bending solid metal there.
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Last edited by riscorpian; 10-24-2014 at 10:49 AM.
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  #3  
Old 10-24-2014, 10:58 AM
Danielr48888 Danielr48888 is offline
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Default

the oil could be the valve gasket i had same issue
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  #4  
Old 10-24-2014, 12:49 PM
Andy9er Andy9er is offline
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Default Re: PLEASE HELP!!! System Too Lean P0171 - Erratic Idle, Check Engine Light

Thanks, I will try the things you mentioned that I wasn't aware of & follow up if it works! (Hopefully it will!)

As far as looking for a leak with the engine on using a spray cleaner (throttle body cleaner), I've already done that a few times with no luck.

I did though gap the spark plugs & it's funny you mentioned that they don't need to be gapped as it said on a few sites, but it was recommended by some to stick with what's provided under the hood...so I'm a little confused on that now. Would that make the engine run lean though???

At high speeds btw, the truck runs fine...it's only when it's idle at almost a stop or parked that the idle is unstable unless the engine light has come on, to which it has already compensated for the lean ratio but will cost me a ton of gas mileage until fixed.

I'm really hoping I won't have to change the intake gaskets!!

I will try a few things you mentioned above & then follow up...

----------

One more thing...anyone by chance have a link or a diagram of my hood layout to locate the things you mentioned above??

Mainly the PCV, EGR, EVAP, brake booster hose, & other vacuum hoses.
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  #5  
Old 10-24-2014, 01:00 PM
riscorpian riscorpian is offline
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Default Re: PLEASE HELP!!! System Too Lean P0171 - Erratic Idle, Check Engine Light

Quote:
Originally Posted by Andy9er View Post
As far as looking for a leak with the engine on using a spray cleaner (throttle body cleaner), I've already done that a few times with no luck.
The PCV valve is hidden insanely well on this engine. Blindly spraying around under the hood won't identify it. To test it, you'll have to get in from the side. Just pull the splash shield off of the inner fender and spray around under the manifold. That's the only way you'll get in the ballpark.

Quote:
Originally Posted by Andy9er View Post
I did though gap the spark plugs & it's funny you mentioned that they don't need to be gapped as it said on a few sites, but it was recommended by some to stick with what's provided under the hood...so I'm a little confused on that now. Would that make the engine run lean though???
I would argue that the importance of that gap is a bit overrated. Yeah, it should be within a certain spec, but there's a reason they give you a range instead of a specific number. Again, if they're the exact plugs your manual calls for, and you made sure the store verified the part numbers, the gap should be fine. That's the advantage of using the plugs your ignition was designed for. If it's way out of that range printed under the hood or in your manual, then yes, it should be adjusted. But the Motorcraft plugs I've seen aren't adjustable, and they've never needed it.

Quote:
Originally Posted by Andy9er View Post
At high speeds btw, the truck runs fine...it's only when it's idle at almost a stop or parked that the idle is unstable unless the engine light has come on, to which it has already compensated for the lean ratio but will cost me a ton of gas mileage until fixed.
All the more reason to suspect a vacuum leak. At high speeds, your engine will suck in so much air that a little leak isn't going to affect much of anything. But at idle, the computer is going out of its way to give the engine as little as possible to keep it efficient. That's when a vacuum leak will start causing problems.

----------

Quote:
Originally Posted by Andy9er View Post
One more thing...anyone by chance have a link or a diagram of my hood layout to locate the things you mentioned above??

Mainly the PCV, EGR, EVAP, brake booster hose, & other vacuum hoses.
There should be a diagram on the radiator bracket thing along with the rest of the labels just under the hood. It's not that helpful, but it gives an idea.

The EVAP hose is just across from the EGR tube, which is the metal tube that feeds from the back of the engine. The EVAP hose itself runs over the purge valve that's just behind the battery. Another hose on that valve runs to the back of the manifold, but also branches off and snakes around to the front of the passenger side. It'll go into a big black baseball-sized thing. That's the vacuum source for your HVAC system.

The 2004 revision won't have an IMRC control or actuator, so disregard any info about that if you find anything. That's '01–'03 only.

The brake booster hose is the one that connects to the top of the manifold near the firewall, and arcs over to the booster that the master cylinder connects to on the driver's side.

The PCV hose is the one on the very back of the manifold, right next to that other weird hose that runs across the engine (the one that splits to the vacuum source and purge valve; it's much much thinner). That's your suspect hose. It'll loop down underneath the manifold to the PCV valve.

Oh, and there is one more hose connecting to the fuel pressure dampener on the fuel rail. It's at the very front of the manifold, just inside it.
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2003 Ford Ranger XLT
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Sonic Blue Pearl with dark gray trim
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  #6  
Old 11-29-2016, 07:56 PM
Kus Kus is offline
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Default Re: PLEASE HELP!!! System Too Lean P0171 - Erratic Idle, Check Engine Light

In need of some knowledge
I have a 2011 4cyl xl two wheel drive 5 speed
Check engine light came on with in a month of installing a cold air intake and p0171 code popped up so I replace the intake sensor and kept the old one. After I replaced the sensor check engine light went away. About 1000 miles later it came back on. So I replaced it again and same thing happened it went away Then came back on after 1000 or so miles so I bought the sensor cleaner and that work for some time. What I'm asking is there a way to have this problem taken away for good without putting on the old airbox.
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  #7  
Old 11-30-2016, 03:01 PM
Soledad Soledad is offline
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Default Re: PLEASE HELP!!! System Too Lean P0171 - Erratic Idle, Check Engine Light

Kus: Is the filter from aFe the type that requires oiling? I know they make dry filters too. Over oiling the filter can cause the oil to coat the sensor in the MAF. Maybe instead of replacing the MAF, try installing a dry filter or if you must run an oiled filter then get some MAF cleaner from a local auto parts store and clean it every so often.

Aside from that, if it's not the MAF or filter then there's a vacuum leak somewhere down steam from the MAF.

EDIT: Ooops, I see you already have the MAF cleaner.
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Last edited by Soledad; 11-30-2016 at 03:08 PM.
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