HELP!! P0302 and P0171

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Jun 21, 2011 | 08:05 PM

MLance12107

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HELP!! P0302 and P0171

Hi everyone! I have a 2000 Expedition XLT with 96,000 miles on it. My check engine light just came on, took it to AutoZone and got codes P0302 and P0171. I've read a little bit on here, and will definitely be checking the hose that everyone seems to have found a hole or crack in, I'm curious as to if I should replace all of my O2 sensors as well. My truck idles rough, the RPM's jump when stopped, and it does not like to go over 55mph without my easing off the gas and then staying steady on it. It gets really jumpy between 50 and 55mph. Any advice you all could offer would be greatly appreciated, I don't have $500 to spend on diagnostics or bull**** repairs that most mechanics seem to mention simply because I have a vagina and they expect me to just say "Ok!" Daddy didn't raise no fool....

Jun 21, 2011 | 08:48 PM

lv2race

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From: The OC

Don't spend all your money on 02 sensors yet. My Expo started running bad right at 97,000 mi. A new set of spark plugs and an IAC cleaning made it run like new. Do you know when or if the spark plugs were ever changed? Has the IAC been cleaned? How old is the fuel filter? A bad COP will do what you describe at 50-55 mph, a stuttering annoying miss. Inspect your COP boots and wire if you change your plugs, use dielectric grease in the boots and anti-seize on the plug thread. Check these links for possible solutions... OBD-II Trouble Code: P0171 System Too Lean (Bank 1) , OBD-II Trouble Code: P0302 Cylinder 2 Two Misfire Detected

Jun 21, 2011 | 09:52 PM

pdqford

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From: Central NYS

Quote:

Originally Posted by MLance12107

I'm curious as to if I should replace all of my O2 sensors as well.

No! Well, at least I wouldn't. Many drivers don't realize that the PCM periodically tests the O2 sensors, first forcing them lean and then rich. The PCM measures the O2 sensors voltage when driven rich and when driven lean to see if they are still in spec. The PCM also measures the time in milliseconds that it takes the O2 sensor to swing from rich to lean and from lean to rich. If the O2 sensor fails the PCM will set a code and turn the SES light on to let you know.

So if the PCM is happy with the O2 sensors performance, so is my wallet.

Jun 22, 2011 | 08:57 AM

MLance12107

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Quote:

Originally Posted by lv2race

The truck is new to me, I bought it in November last year and since I've had it, it's only ever had a regular oil change and been in the shop last month to replace a cracked ring when my air ride suspension went out. I pulled the carfax on it and it's only had 1 owner before me, she drove it less than 9,000 miles a year after buying it brand new, it's never had any major work done as far as Carfax is concerned, so I'm assuming all parts are factory original. I drove it this morning, and it drove perfectly! I live in Houston, Tx, so it's been in the high 90's lately..today with the rain it's at 69 degrees, I'm wondering if that has anything to do with it. All of my gauges are reading normally, it's not running hot at all. My hubby would rather put it in the shop, let them pinpoint exactly what's wrong, but I prefer to fix it myself if I can.

Jun 22, 2011 | 01:07 PM

lv2race

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From: The OC

Quote:

Originally Posted by MLance12107

My hubby would rather put it in the shop, let them pinpoint exactly what's wrong, but I prefer to fix it myself if I can.

Sounds like you got a good Expo, just a little maintenance to bring it back to new. A few things to note, the shop (Ford) will probably charge you $300 - $500 to change just the plugs, which is why you should take the time and do DIY. If you or your hubby are mechanically inclined, it will take you a few hours. Here is what I suggest. Replace these first with Motorcraft parts; Plugs about $3.50 each (verify plug gap), Fuel filter $13 and a few hours of your time. You'll need these to remove the fuel filter available at any auto parts store for a few bucks. K-D Tools 3530 6 Pc. Low Profile Fuel Line Disconnect Set - Toolfetch.com Clear your codes and drive for a while. As I said earlier, check the boots for cracks/splits and replace as necessary. Apply dielectric grease to the boot and anti-seize to the plug thread. Start with the cheap fixes first and if it doesn't fix you, let us know and we'll go from there. If you decide to do the plugs, we can walk you through that too.

Jun 22, 2011 | 02:15 PM

r2millers

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From: Southern Cal

JL is right. Start simple and check the egr rubber tee if that's what you were referring to in your original post. When that cracks and starts to leak, you will get "lean" firing codes.
Besides the great suggestions above, especially using anti sieze and dielectric grease on those coil packs, you might think about changing out the tranny fluid and filter. Ford recommends between 35-50k but 100k definitely makes it time. If towing and having a limited slip rear end, also change out the rear end oil with synthetic.
Some inexpensive maintenance here will go a long way to prevent the big ones.