2001 2.3L code P0171

infamousmx664 · Jan 9, 2012

Hi I think I have tried everything and searched as much as possible to solve this check engine light problem. The truck has a slightly rough idle, throws code P0171 bank 1 too lean, spits black soot from the tail pipe, and sometimes i feel a power surge after 3500 rpms ehen im driving in say 2nd gear.

I have already replaced/removed the following;

new spark plugs
new air filter (oiled K&N)
switched MAP sensor with one I know works with no CEL
new valve cover gasket
inspected and cleaned intake manifold gasket
inspected and cleaned throttle body gasket
inspected and cleaned upstream O2 sensor
new plug wires
inspected coil pack
new thermostat
new oil pressure sensor
checked vacuum lines
new oil
new oil filter
new 50/50 coolant

can anyone HELP me with what might be the cause. i think the truck has been getting poor fuel economy because of this as well.... like 24mpg highway, where i should be seeing 27~

infamousmx664 · Jan 10, 2012

If I let it idle for a few minutes it will sometimes drop to 600rpm and then bounce back to 1100rpm and eventually level back out at 900rpm.

Does anyone think I should buy a new upstream O2 sensor to try and rule that out?

infamousmx664 · Jan 10, 2012

I am going to clean the MAF with CRC mass air flow cleaner tonight and switch the upstream O2 sensor out with one I know works. We'll see if this works. If not mabye my intake manifold has a pin hole/small crack but I didn't notice anything when I had it off and cleaned it.

rocketalpha · Jan 14, 2012

My advice get somebody with a scanner and monitor your fuel trims, and O2 Sensor. Verfy that it is running lean. Then go threw your typical lean diagnostics.

Tests/Procedures: 1. Check the oxygen sensor voltage. If the voltage is low at all times, attempt to enrich the engine by spraying propane or carburetor cleaner into a vacuum line.

2. If the voltage is still low, unplug the oxygen sensor, the engine will likely now run better.

3. Now check the output voltage of the oxygen sensor. If it still remains low at all times, but the engine runs better with it unplugged, suspect a failed sensor.

4. If the voltage is normal unplugged, but drops to zero when plugged in, suspect a circuit fault between the sensor and the Powertrain Control Module (PCM).

Sent from my ZTE-Z990 using Tapatalk

rocketalpha · Jan 14, 2012

Also get some body to power brake it , at about that 3500 Rpm mark and then check for arching around the coil packs. I would test it with my spark checker, and do it in each cylinder.
good luck.
Sent from my ZTE-Z990 using Tapatalk

hogvibrator · Jan 24, 2013

i had the same thing.it was the iac. (idle air control valve).replaced it,cant clean it on a 2.3 litre,2002 reg cab.54.00$ at auto zone.

crazypj · Feb 6, 2013

Had same code on wife's car,turned out to be a tiny split in the rubber boot between air filter and throttle body
Meant the MAF was sending wrong reading

jaynine89 · Jan 1, 2014

I have the same truck, 2001 with the 2.3L, and I've had the same code set off my Check Engine light as well. The thing is it only seems to trigger on really cold mornings (0F). Is there any correlation there? Maybe moisture creating a short in a sensor somewhere? The truck doesn't seem to run any different, in fact if the light didn't come on, I wouldn't know there was a problem. I find it interesting that it says it's running lean, though, as my gas gauge seems to drop as if I were running really rich.

adsm08 · Jan 1, 2014

In many cases running lean will use more fuel because it is trying to match excessive incoming air, or at least it thinks it is trying to.

jaynine89 · Jan 1, 2014

That's interesting. I'd think that if it were running lean, it wouldn't be putting enough gas into the system at all, whereas running rich would just be dumping it in. But that makes sense.

So do you think mine is triggering just because of the cold? Like I said, it only seems to happen on especially frigid mornings when the truck has sat outside all night. The last couple weeks in Madison, we had a few nights where the temperature got down as low as -12F.

Donaldh · May 11, 2014

Vacuum hose P0171

Also have the P0171 code. Here is my journey(275,000miles) . Found leaking vacuum hose, 90 boot, to the air intake duct and replaced it. I replaced plugs and wire set, tested/cleaned the MAF, replaced PCV. Decided to replace HO2S(both). All this seemed to help, but was still smelling like it was running lean, code still in. After checking vacuum hoses again, found another leak at 90 boot on the back end of the intake manifold. It runs down between the firewall and engine. Was able to place a smaller hose into the boot and tape it, Eureka! Problem solved runs Great again! BUT can't locate the other end of this hose. Can anyone help? I would like to replace with new hose.

2001 2.3L code P0171

New Member

New Member

New Member

New Member

New Member

New Member

Member

New Member

Senior Master Grease Monkey

New Member

New Member

Sponsored Ad

Sponsored Ad

Today's birthdays

Member & Vendor Upgrades

Truck of The Month

Recently Featured

Follow TRS On Instagram

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store

Sponsored Ad

Sponsored Ad

Sponsored Ad

Amazon Deals