|11-27-2007, 08:36 AM||#1|
How to determine a vacuum leak or lack of fuel
OK I have been having issues running lean, bank 1. This is how to determine if it is caused by a vacuum leak, or lack of fuel from a plugged filter or a bad injector.
Quite long, and might want to sticky..
This FORD Technical Service Bulletin will help you determine if you have a vacuum leak, but you have to be able to read Short & Long Term Fuel Trims. The TSB will have you check this ECM fuel command, at idle and then again at 2500 rpm, to see if the lean condition is from an air leak still or a lack of fuel.
Basically, if you are not running lean at 2500 rpm, you still have an air leak. The higher RPM can overcome air leaks. But if it's fuel delvery related, the vehicle will continue to run lean under a higher rpm. (plugged injectors or filter, weak pump, etc.). Monitoring the computer's fuel delivery commands tells us what is going on. If the ECM is adding fuel (+ xx%) , it's lean...if it's subtracting fuel (- xx%), it's cuz you are too rich.
MALFUNCTION INDICATOR LAMP (MIL) TSB 04-17-4
ILLUMINATED—SYSTEM LEAN DIAGNOSTIC
TROUBLE CODES (DTC’S)—SERVICE TIPS
2000 Contour 2000-2002 Continental
2000-2002 Escort 2000-2004 LS, Town Car, Navigator
2000-2003 Escort ZX2 2002-2003 Blackwood
2000-2004 Crown Victoria, Focus, Mustang, 2003-2004 Aviator
2000-2004 Econoline, Excursion, Expedition,
2000-2004 Grand Marquis, Sable,
Explorer, F-Super Duty, Ranger
This article is intended to aid in diagnosing DTC’s FREEZE FRAME DATA WILL INDICATE THE
P0171, P0174, P1130, P1131, P1150, P1151, ENGINE AND AMBIENT CONDITIONS WHEN THE
P2195, or P2197 (system lean or lack of HEGO DTC WAS SET. THESE ARE IMPORTANT
switches) when a vacuum leak is present. HEGO BECAUSE THE VACUUM LEAKS MAY OCCUR
sensors, MAF sensors, and PCM replacements are ONLY WITHIN SPECIFIC TEMPERATURE
not an effective repair when a vacuum leak is RANGES AND MUST BE DUPLICATED TO
causing the above DTC’s. DETECT THE LEAK.
Perform the following inspections/repairs when the FUEL TRIMS AT IDLE ARE PARTICULARLY
above codes are found in memory. Procedure SENSITIVE TO VACUUM LEAKS SINCE THE
provides instructions on how to make comparisons UN-METERED AIR “LEAKAGE FLOW” IS A
of the total fuel corrections (using scan tool or HIGHER PERCENTAGE OF TOTAL AIRFLOW AT
equivalent) at idle and high RPM’s to help IDLE THAN AT PART THROTTLE. THE
determine if a vacuum leak is the root cause of the BAROMETRIC PRESSURE (BP) PID IS NOT
DTC’s. RECOMMENDED TO VIEW WHEN DIAGNOSING
A VACUUM LEAK. BP IS AN INFERRED PID
SERVICE PROCEDURE CALCULATED DURING HIGHER ENGINE LOADS.
NOTE 1. Perform preliminary inspection, retrieve and
FREEZE FRAME AND ADAPTIVE FUEL VALUES record DTC’s and Freeze Frame Data. DO
(ASSOCIATED WITH “LONGFT” PID) WILL NOT NOT PERFORM KAM RESET OR OBDII
BE AVAILABLE IF A KAM OR OBDII RESET WAS RESET (CLEAR CODES) AT THIS TIME,
RECENTLY PERFORMED. ADAPTIVE FUEL TABLES MUST BE INTACT
FOR THIS PROCEDURE.
NOTE: The information in Technical Service Bulletins is intended for use by trained, professional technicians with the knowledge, tools, and equipment to do
the job properly and safely. It informs these technicians of conditions that may occur on some vehicles, or provides information that could assist in proper
vehicle service. The procedures should not be performed by “do-it-yourselfers”. Do not assume that a condition described affects your car or truck. Contact a
Ford, Lincoln, or Mercury dealership to determine whether the Bulletin applies to your vehicle. Warranty Policy and Extended Service Plan documentation
determine Warranty and/or Extended Service Plan coverage unless stated otherwise in the TSB article.The information in this Technical Service Bulletin
(TSB) was current at the time of printing. Ford Motor Company reserves the right to supercede this information with updates.The most recent information is
available through Ford Motor Company’s on-line technical resources.
Copyright ã 2004 Ford Motor Company PAGE 1
TSB 04-17-4 (Continued)
a. If DTCs are continuous, or if other DTC’s or e. Determine total fuel correction at idle for an
drive symptoms are present other than at in-line 4 cylinder engine or bank 1 of a
idle, diagnose and repair those V-engine by adding LONGFT1 to SHRTFT1.
codes/symptoms first. Determine total fuel correction for bank 2 of
a V-engine, by adding LONGFT2 to
b. Perform visual inspection - look for SHRTFT2.
disconnected/broken/cracked vacuum hoses
especially near vacuum trees. Check PCV NOTE
elbows for cracks or loose connection. MAKE SURE ONLY THE CORRECT BANKS AND
Confirm vehicle has the correct PCV valve TRIMS ARE ADDED TOGETHER (DO NOT ADD
installed. If a suspect vacuum leak is found LONGFT1 TO LONGFT2 OR LONGFT1 TO
proceed to Step 4. SHRTFT2.)
NOTE • EXAMPLE 1: BANK1 LONG FUEL TRIM;
EACH VEHICLE APPLICATION REQUIRES A PCV LONGFT1 = +13% AND SHORT FUEL TRIM;
VALVE CALIBRATED FOR THAT VEHICLE. SHRTFT1 = +23%. THE TOTAL CORRECTION
MOTORCRAFT PARTS ARE STRONGLY ON BANK1 IS +36% (13%+23%=36%).
RECOMMENDED. ALSO, THERE WILL BE A • EXAMPLE 2: BANK2 LONGFT2 = +24% AND
NORMAL VARIATION IN FUEL TRIMS FROM BANK 2 SHRFT2 = -3%. THIS TOTAL FUEL
VEHICLE TO VEHICLE. CORRECTION ON BANK 2 IS +21% (+24%
2. Determine if vacuum leak is present. A TYPICAL VACUUM LEAK WHICH MAY SET A
LEAN CODE DTC WILL HAVE TOTAL
a. Set up scan tool to monitor the following
CORRECTION OF AROUND +20% OR GREATER
PIDS: ECT/CHT, LONGFT1, LONGFT2,
AT OR NEAR IDLE (DEPENDS ON CALIBRATION)
SHRTFT1, SHRTFT2, IAT.
f. Depress and hold throttle pedal to maintain
b. Start the engine and run at idle with all
an engine RPM of 2500.
accessories off - gear lever in Neutral/Park.
g. Observe PIDS with engine RPM at 2500.
c. Run engine until ECT/CHT matches the
View and record LONGFT1, LONGFT2,
corresponding freeze frame data from Step
SHRTFT1, SHRTFT2. Do not hold engine
1. This will duplicate the customer’s engine
RPM’s at 2500 for more than 20 seconds.
operating temperatures when the DTC was
Release pedal and repeat if more time is
set in memory. Hood may remain open
necessary to record PIDS.
during this test to help reduce ECT/CHT/IAT
temperatures. Keep IAT below 115° F (46° h. Determine total fuel correction at 2500
C). RPM’s by adding the LONGFT’s to the
d. Record LONGFT’s and SHRTFT’s.
i. If the fuel correction decreases, more than NOTE
15%, (example: was +31% at idle on bank 1
TO PREVENT HIGH ECT/CHT AND IAT but changed to +12% at 2500RPM on bank
TEMPERATURES IT MAY BE NECESSARY TO 1, a decrease of 19%) then a vacuum leak
PERFORM THIS TEST WITH THE ENGINE is most likely causing the lean diagnostic
RUNNING FOR SHORT INTERVALS, ESPECIALLY test codes. Proceed to Step 3.
WHEN AMBIENT TEMPERATURE IS ABOVE 85° F
(29°C). USE OF A GARAGE FAN WILL HELP TO j. If the total correction remains approximately
KEEP ENGINE TEMPERATURES STABILIZED the same then the lean condition is not
DURING TEST. IT MAY BE NECESSARY TO RUN caused by a vacuum leak. Refer to the
THIS TEST AT SPECIFIC ECT/CHT/IAT PC/ED for further diagnostics.
TEMPERATURES, REVIEW FREEZE FRAME
DATA. EXAMPLE: IF ECT WAS AT 160° F (71° C) 3. Pinpointing vacuum leaks.
THEN ENGINE MAY NEED A COLD START TO a. Monitor SHRTFT’s with scan tool with
DUPLICATE THIS TEMPERATURE. engine running at idle.
TSB 04-17-4 (Continued)
b. Locate vacuum trees off air induction d. If vacuum leak is located proceed to Step
system and PCV system. Use hose clamp 4c.
or pinch off pliers (avoid tools with sharp
INTAKE GASKETS OR MANIFOLD LEAKS
NOTE CANNOT BE DETECTED BY PINCHING OFF
USE CAUTION WHEN CLAMPING HOSES. A LINES. USE OTHER LEAK DETECTION
VACUUM CAP OR EQUIVALENT CAN ALSO BE METHODS, SUCH AS SMOKE TEST, SONIC
USED TO BLOCK THE VACUUM SOURCE TO A TESTS, AND PROPANE.
SPECIFIC SYSTEM. DO NOT TRY TO PINCH OFF
A HARD PLASTIC HOSE OR CONNECTION, TRY e. If no vacuum leaks are found, refer to the
ISOLATING BY CAPPING. CLAMPING OF THE PC/ED for further diagnostics.
FUEL SYSTEM PURGE HOSE MAY SHIFT 4. Verification of repair.
SHRTFT DURING PURGING MODES, USE
VISUAL INSPECTION ON THIS HOSE IF a. Prepare scan tool and vehicle to monitor
RESULTS ARE NOT CONSISTENT. short term fuel trims (SHRTFT’s).
c. Observe short fuel trims when pinching b. Get vehicle into stabilized idle condition,
specific vacuum lines. The SHRTFT values unless freeze frame indicates other
should decrease more than 15% towards temperatures.
the negative direction, if a vacuum leak was
pinched off. (wait up to 20 seconds to c. Repair vacuum leak.
observe if pinch has any effect on d. SHRTFTs should decrease by at least 15%.
SHRTFT’s). If they do not, return to Step 2.
NOTE e. Clear KAM and codes.
EXAMPLE: PINCH OFF THE BRAKE BOOSTER
VACUUM HOSE (DO THIS ONLY IN PARK) AND WARRANTY STATUS: Eligible Under Provisions Of
OBSERVE SHRTFT’S. IF THE SHRTFT’S New Vehicle Limited
DECREASES, BY MORE THAN 15%, A VACUUM Warranty Coverage And
LEAK IS PRESENT. IF THE SHRTFT1 WAS AT Emissions Warranty
+14% BEFORE PINCHING THEN SHIFTS TO -7% Coverage
AFTER PINCHING, TOTAL SHIFT OF 21%
TOWARDS NEGATIVE DIRECTION.
good luck all.....
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