Contour Enthusiasts Group Archives Forums General Troubleshooting P0171

Hey all, I keep getting a 171 code. All I have been told is that it is the o2 sensor, no one can tell my how to check to determine which one. I looked at the MAF. It looks as though one of the filimints in it is toast. When the car is started cold you can't rev up the engine, it will kill it. It has to be running for a minute. When at a stop in gear the engine revs up and down, but much more so with the A/C on. Often when starting out from a stop it will die.\


Thanks for the help.

Check for vacuum leaks in the engine bay (hissing sound or something similar).

Also clean the MAF sensor (as you say it looks like one of the filaments are toast).

From TSB,

P0171 - System Too Lean (Bank 1) The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The code is set when the adaptive fuel tables reach a rich calibrated limit.

Fuel System:
�· Contaminated fuel injectors
�· Low fuel pressure or running out of fuel (fuel pump, filter, fuel supply line restrictions)
�· Vapor recovery system (VMV)

Induction System:
�· MAF contamination
�· Air leaks between the MAF and throttle body
�· Vacuum leaks
�· PCV system concern
�· Improperly seated engine oil dipstick

EGR System:
�· Leaking gasket
�· Stuck EGR valve
�· Leaking diaphragm or EVR

Base Engine:
�· Exhaust leaks before or near the HO2S
�· Secondary air concern

Powertrain Control System:
�· PCM concern

Edit. MAF sensor

http://www.contour.org/mods/mods.php?s=howto&displayid=36
and
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=zetecmaint&Number=989728&page=&view=&sb=5&o=&fpart=1&vc=1
and
http://www.autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/1b/cb/25/0900823d801bcb25.jsp

I sprayed ether all over the engine area. I couldn't get anything from it. What do I clean the MAF with, and where do I get it?

Thanks

Okay. I got some Gunk Non-Chlorinated Carb-Medic cleaner and clean the ol' MAF up with the help of a Q-Tip. I un did the battery cable for a bit to clear the fault. I fired up the car and drove about 10 miles. The CEL did not return. The engine stopped surging while in gear with the A/C on, but it was still running a bit rough, even with the A/c off. In park she purrs like a kitten, but when the accelerator is depressed there is a hesitation still there.

What next? Seems like we are making progress.

Thanks

Change the fuel filter and clean the IAC valve.


Fuel filter.
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=v6maint&Number=958655&page=0&view=collapsed&sb=5&o=186&fpart=1


IAC cleaning
Zetec IAC location.

For the Zetec I-4, you need to access the IAC from the bottom of the car.

IAC cleaning
from Ray's UIM/LIM how to in Duratec Maintenance how to.

"Replacing the IAC gasket:
(From IAC faq)
Over time, the IAC (Idle Air Control) valve becomes sticky due to buildup from the EGR and PCV systems. It can stick partially open such that idle quality is adversely affected, and engine RPM's will not drop below 1500. For a while, blipping the throttle will restore normal idle, but this only works for so long.

The fix is to remove the IAC valve by unbolting the two 8mm bolts that hold it on and disconnected the wiring plug. If you are careful enough, replacement of the gasket will not be necessary. The gasket costs less than US $1.00, so it is no tragedy if you destroy it. Once the valve is off, spray it out with some carb/intake cleaner and make sure any gunky residue is gone. Reattach, and you are done. It is a lot cheaper than a new IAC, which runs around US $70. Note: Ford claims the IAC cannot be cleaned, but this is not true in my experience." Ray.

Location of the IAC for the Zetec.

"It's on the back side of the intake plenum under the throttle body area." DESIGN.

I looked at the Haynes manual and the Zetec IAC valve is located next to the starter. Below are the steps from the 1996 Ford CD to remove it .

Idle Air Control (IAC) Valve


Removal

1. Disconnect battery ground cable

2. Remove the air cleaner outlet tube and resonator assembly.
3. Disconnect the main chassis vacuum line.

4. Disconnect the ignition coil and radio interference capacitor wiring.

5. Remove the fuel line bracket retaining bolt.

6. On 2.0L engine equipped vehicles, raise vehicle on hoist.
7.
7. Disconnect the engine control sensor wiring or fuel charging wiring (depending upon application) from the idle air control valve (IAC valve) at the idle air control valve connector.

8. On 2.5L engine equipped vehicles, remove retainer for engine control sensor wiring from the upper retaining stud bolt.

9. Remove the two idle air control valve retaining bolts or stud bolt (depending upon application).

10. Remove the idle air control valve and idle air control valve gasket.

Installation

1. Note: If scraping is necessary, be careful not to damage idle air control valve or intake manifold idle air control valve gasket surfaces or drop material into intake manifold.

Clean idle air control valve gasket mating surfaces.

2. To install idle air control valve, reverse Removal procedure. Tighten the fuel line bracket bolt to 8-12 N-m (71-106 lb-in).

3. On 2.5L engine equipped vehicles, tighten the retaining bolt and stud bolt to 8-12

4. On 2.0L engine equipped vehicles, tighten the idle air control valve retaining bolts to 8-11 N-m (71-97 lb-in).