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Discussion Starter #1
My engie light came on monday morning on my way to work. Everything seamed like it was all working fine no hesitation or stumbling or rought idle. Had the guys at Discount auto parts pull the codes for me with there reader and we got a P0171 - System lean. Wound a leaking Brake booster make this code come up? I know mine is leaking cause I can hear a leak when I step on hte Brake pedal now as well.
 

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yo,
Brake Booster! Possibly, check vac line; any signs of a vacuum leak?
On idling engine; "...Check for vacuum leaks using a mechanic's stethoscope with the probe removed, or a ~3' garden hose. Don't spray flammables on a running engine. Also check the brake booster, the 2ndry air (coffee can) & HVAC vacuum reservoirs..." around intake manifold; and maybe under dash behind control panel vac line area (by Steve83's & Miesk5)
You have Cruise Control? Did you get the Recall work done esp the Field Action??? If not, do NOT park next to your home or use an attached garage to park it
Recall for 94-96 Bronco, 94-02 F-150, 97-02 Expedition & 98-02 Lincoln Navigators; NHTSA CAMPAIGN ID Number: 05V017000; Recall Date JAN 27, 2005 & Update; (search for 05V017000 in "Safety Recalls)' ON CERTAIN SPORT UTILITY VEHICLES AND PICKUP TRUCKS, THE SPEED CONTROL DEACTIVATION SWITCH MAY OVERHEAT, SMOKE, OR BURN THIS CONDITION COULD LEAD TO A FIRE. FIRES HAVE OCCURRED WHILE THE VEHICLES WERE PARKED WITH THE IGNITION 'OFF.' AS AN INTERIM REPAIR, OWNERS WILL BE INSTRUCTED TO RETURN THEIR VEHICLES TO THEIR DEALERS TO HAVE THE SPEED CONTROL DEACTIVATION SWITCH DISCONNECTED. AS SOON AS REPLACEMENT PARTS ARE AVAILABLE (EARLY APRIL 2005), OWNERS WILL BE INSTRUCTED TO RETURN TO THE DEALERS FOR INSTALLATION OF A NEW SWITCH FREE OF CHARGE. OWNERS MAY CONTACT FORD AT 1-800-392-3673. (NOTE: ALSO SEE RECALLS 05V388 AND 06V286) FORD RECALL NO. 05S28. CUSTOMERS MAY ALSO CONTACT THE NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION'S VEHICLE SAFETY HOTLINE AT 1-888-327-4236 (TTY 1-800-424-9153), OR GO TO HTTP://WWW.SAFERCAR.GOV
Source: by National Highway Traffic Safety Administration nhtsa.dot.gov

Recall Update; Field Service Action 05S28 Speed Control System Modification Supplement #7 for 94-96 Bronco, 94-02 F-150/250 (Under 8500 GVW), 97- 02 Expedition, 98-02 Navigator, 02 Blackwood
Source: by Ford via Steve83 (Steve, That dirty old truck) at SuperMotors.net


Recall; Fused Jumper Harness (14A411) pic; "List price on this is ~$11 (as of the date I posted the pic), but it will be installed at NO CHARGE (parts or labor) on vehicles covered by the recall. Even though the label is wrong about the fuse being internal, it should still NEVER be replaced. If it blows, it means the brake pressure switch is leaking, and (as the label states) should be replaced with the new switch & adapter harness kit, listing for ~$20 right now..."
Source: by Ford via Steve83 (Steve, That dirty old truck) at SuperMotors.net


here is da skinny on;
DTC P0171 - System to Lean (Bank 1); "... The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit. 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 ..."
Source: by slingblade


DTC P0171 & P0174 Lean Troubleshooting; "...These codes commonly occur on many Ford vehicles, and are set when the powertrain control module (PCM) sees the air/fuel mixture is running too lean (too much air, not enough fuel). Unmetered air can enter the engine through a vacuum leak, a dirty airflow sensor (MAF) that is not reading airflow accurately, an EGR valve is not closing (DPFE) and is leaking exhaust into the intake manifold, an EGR valve that is allowing too much flow (because the EGR differential pressure sensor that monitors EGR flow is faulty and is under-reporting EGR flow). If the problem is not enough fuel, the underling cause may be a weak fuel pump, restricted fuel filter, leaky fuel pressure regulator or dirty fuel injectors..."
Source: by Larry C



Suggest someday you get an Official FORD Bronco Electrical and Vacuum Troubleshooting Manual (EVTM), Powertrain Controls and Emission Diagnosis Manual (PCED) CD from Steve83, E bay for all pinpoint tests.
Best ~$7.00 to $10.00 you'll ever spend on the Bronco repairs.
Use the Search (Advanced Search) function for him here; then use the email option.
 

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:stupid

This guy is the $HIT!!!! always good info and even referenced to back it up... Do what he says :thumbup
 

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I had the same thing pop up on my 01 trans am... couldnt figure it out until I saw that the hose on one end of the pcv valve had melted thru... I replaced this hose and after clearing the code it went away and has not been back...
 

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Discussion Starter #5
I know it's the Brake booster cause the other week I heard a vacum leak sound as I steped on the Brake pedal. Just didnt get a light to pop till monday morning. I have been suspecting the diaphram has been slowly tearing for the past few weeks cause of a squeeling sound I heard a while back from under the dash. was just wondering if it could possibly toss a code for lean condition. Guess i wont worry about the light if it comes on again. Have it cleared for now. Next on the list is a hydro Booster I gues lol. was hopin to save up for a lift....gonna have to wait for a while now again.
 

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just had a booster go out on a 92 suburban and it didnt code, I know its OBD1 but maybe the OBD2 would...
 
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