1999 Chevy Tahoe accelaration

Tiny
JUATA
  • MEMBER
  • 1999 CHEVROLET TAHOE
  • V8
  • 4WD
  • AUTOMATIC
  • 11,000 MILES
Over the last month my 99 5.7 4WD Tahoe has been giving me problems accelerating when I give it a heavy foot. When I hit the gas down it loses acceleration almost like it's being starved of air or gas. When I hit the gas the engines just bogs down, begins to hesitate, and will not accelerate.

It'll drive ok if I'm light on the pedal; and the engine feels smoother than ever.

i already replaced the mass airflow sens, plugs and cables, egr valve, distributor, and air sensor, my fuel pump is about 4 yrs old and my fuel filter is 5 months old.

i get all this but my check engine light does not come on. Only my service engine soon light turns on
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Wednesday, April 8th, 2009 AT 7:44 AM

5 Replies

Tiny
MERLIN2021
  • EXPERT
The service engine soon light is telling you the PCM(computer) has identified and stored a fault code. Get the code(s) read. Autozone will do it free, then post the codes here.
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Wednesday, April 8th, 2009 AT 7:47 AM
Tiny
JUATA
  • MEMBER
Yeah I already went to autozone they dont do that no more but ill get it done somewhere
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Wednesday, April 8th, 2009 AT 7:52 AM
Tiny
ZACKMAN
  • MEMBER
Could you have been mistaken?

O'Reilly no longer offers the service, though they will let you borrow the scanner and you can do it yourself. This is from O'Reilly's corporate office.

I just called two Autozone stores and they both said that they would still do the test for free.
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Wednesday, April 8th, 2009 AT 9:07 PM
Tiny
JUATA
  • MEMBER
WELL HERE ARE THE CODES THAT I GOT

P0171
P0174
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Friday, April 17th, 2009 AT 5:19 PM
Tiny
MERLIN2021
  • EXPERT


http://www.2carpros.com/forum/automotive_pictures/62217_tahoea_1.jpg



http://www.2carpros.com/forum/automotive_pictures/62217_tahoeb_1.jpg


This means not enough fuel, if you have the right test equipment and technical skill you can diagnose if it's because of the fuel pump, or the MAF, or a vacuum leak. Or even a bad oxy sensor. here's how to test the fuel pressure.
http://www.2carpros.com/car_repair_video/test_fuel_injection_pressure.htm
Go here and checkout our video.
DTC P0171: FUEL TRIM SYSTEM LEAN-BANK 1 (4.8L, 5.3L & 6.0L "C" & "K" SERIES & 5.7L "F" & "Y" BODIES) Circuit Description PCM monitors oxygen sensor signal voltage and adjusts fuel delivery based on signal voltage. A change made to fuel delivery is indicated by long and short term fuel trim values. Short term fuel trim values change rapidly in response to HO2S signal voltages. These changes fine tune engine fueling. Long term fuel trim values changes in response to trends in short term fuel trim. Long term fuel trim makes coarse adjustments to fueling in order to re-center and restore control to short term fuel trim. Long term and short term fuel trim can be monitored by use of scan tool. Ideal fuel trim value is about zero percent. A positive fuel trim indicates that PCM is adding fuel to compensate for a lean condition. A negative fuel trim indicates that PCM is reducing amount of fuel to compensate for rich condition. DTC will set if PCM detects an excessively rich or lean condition. For duplication of DTC, ensure: DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0300, P0335, P0336, P0351-P0358, P0401, P0404, P0405, P0410, P0412, P0418, P0443, P0500, P0502, P0503, P1111, P1112, P1258, P1404, P1415 or P1416 are not set. Engine coolant temperature is 120-239 F (60-115 C). BARO is greater than 74 kPa. MAF is 5-90 gm/s. MAP is 26-90 kPa. IAT is -4-194 F (-20-90 C). Engine speed is 400-3000 RPM. TP sensor angle is less than 90 percent. Vehicle speed is less than 85 MPH. Fuel level is greater than 10 percent. PCM detects average long term fuel trim cell values are more than a predetermined threshold. Diagnostic Procedures 1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, go to next step. NOTE: For circuit reference, see appropriate wiring diagram in WIRING DIAGRAMS article. NOTE: If other DTCs are present, except P0174, diagnose affected DTCs first. Page 1 of 2 TESTS W/CODES - DTC P0135-P0204 -1999 Chevrolet Tahoe 2. Start and warm engine to normal operating temperature. Ensure system is in "closed loop". Using scan tool, select FUEL TRIM DATA LIST and monitor LT FT BN 1. If LT FT is less than 23 percent, go to next step. If values are not as specified, go to step 4 . 3. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME and/or FAILURE RECORDS data and note parameters. Turn ignition off for about 15 seconds. Start engine and operate vehicle within conditions required for this diagnostic to run, and as close to conditions recorded in FREEZE FRAME/FAILURE RECORDS as possible. Select DTC function then enter DTC P0171. If scan tool indicates that this test failed this ignition, go to next step. If scan tool does not indicate that this test failed this ignition, see DIAGNOSTIC AIDS . 4. If DTC P0174 is also present, go to next step. If DTC P0174 is not present, go to step 6 . 5. Check vacuum hoses for splits, kinks and proper routing. MAF sensor, air induction system, throttle body, intake manifold, PCV system and EGR valve for vacuum leaks. Check for fuel contamination. Check for good PCM and sensor grounds. Check engine mechanical condition. Repair as necessary. After repairs, go to step 7 . If engine mechanical repairs are not necessary, diagnose fuel system. See appropriate SYSTEM & COMPONENT TESTING article. 6. Check bank 1 for exhaust leaks or loose exhaust hardware. Ensure oxygen sensor is properly installed. Check vacuum leaks that will affect bank 1 only. Check engine mechanical condition. After repairs, go to next step. If repairs are not necessary, diagnose fuel system. See appropriate SYSTEM & COMPONENT TESTING article. 7. Repair or replace any faulty items. After repairs, go to next step. 8. Using scan tool, clear DTCs. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0171. Operate vehicle within conditions that set this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, go to step 2 . 9. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no undiagnosed DTCs are displayed, system is okay. Diagnostic Aids If DTC P0171 cannot be duplicated, problem could have been caused by engine running out of fuel. A fuel delivery malfunction will cause DTC to set. Check all items that can cause a lean condition.
4.3L, 5.0L, 5.7L & 7.4L 1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step. 2. Turn ignition off. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF . Connect Fuel Pressure Gauge (J-34730-1A) to fuel pressure test port. Using scan tool, command fuel pump on. Bleed air out of fuel pressure gauge into container. Monitor fuel pressure with fuel pump running. Fuel pressure should be 60-66 psi (4.2-4.6 kg/cm 2 ) on CSI system and 56-62 psi (4.0-4.4 kg/cm 2 ) on SFI system. If fuel pressure is as specified, go to next step. If fuel pressure is not as specified, go to step 8 . 3. Using scan tool, command fuel pump on. Fuel pump should run for 2 seconds. Observe fuel pressure after fuel pump stops running. After fuel pump stops, fuel pressure should stabilize and remain constant at 55-60 psi (3.9-4.2 kg/cm 2 ) on CSI system and 48-52 psi (3.4-3.7 kg/cm 2 ) on SFI system. If pressure is within specification and holds, go to step 5 . If pressure is not as specified, go to next step. 4. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF . Disconnect fuel filter. Drain any remaining fuel from fuel pipes into container. Install appropriate fuel line shutoff valve in place of fuel filter. Open shutoff valve. Using scan tool, command fuel pump on. Check for leaks at shutoff valve. Start engine and idle for 30 seconds. Turn ignition off for 10 seconds. Turn ignition on with engine off. Using scan tool, command fuel pump on. Wait for fuel pressure to build. Close shutoff valve. Fuel pressure should remain constant at 55-60 psi (3.9-4.2 kg/cm 2 ) on CSI system and 48-52 psi (3.4-3.7 kg/cm 2 ) on SFI system. If pressure is as specified and holds, go to step 12 . If pressure is not as specified, go to step 6 . 5. If fuel pressure is suspected of decreasing during acceleration, cruise or hard cornering, go to step 27 . If fuel pressure is not suspected of decreasing during acceleration, cruise or hard corning, go to step 26 . 6. Check fuel feed line between shutoff valve and fuel pipes. If fuel feed line is faulty, go to step 25 . If fuel feed line is okay, go to next step. 7. Open shutoff valve. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF . Disconnect fuel return pipe union located near fuel filter. Drain remaining fuel from fuel pipes into container. Install appropriate fuel line shutoff valve in place of fuel return pipe union. Open shutoff valve. Using scan tool, command fuel pump on. Check for leaks at fuel shutoff valve fittings. Start engine and idle for 30 seconds. Turn ignition off for 10 seconds. Turn ignition on with engine off. Using scan tool, command fuel pump on. Wait for fuel pressure to build. Close shutoff valve installed on fuel return pipe. If fuel pressure remains constant, go to step 22 . If fuel pressure does not remain constant, go to step 29 . 8. Turn ignition on with engine off. Using scan tool, command fuel pump on. Fuel pump should run for 2 seconds, and then turn off. Observe fuel pressure after fuel pump stops running. If fuel pressure is present, go to step 13 . If fuel pressure is not present, go to next step. 9. Using scan tool, command fuel pump on. Listen for operation of fuel pump. If fuel pump operates, go to next step. If fuel pump does not operate, see appropriate FUEL SYSTEM ELECTRICAL CIRCUIT under NO START DIAGNOSIS . 10. Check for restricted fuel filter, fuel pump strainer or fuel line. If a problem is found, go to next step. If no problem is found, go to step 12 . 11. Repair or replace as necessary. After repairs, go to step 30 . 12. Replace fuel sending unit assembly. After repairs, go to step 30 . 13. Turn ignition on with engine off. Using scan tool, command fuel pump on. Fuel pump should run for 2 seconds. Observe fuel pressure. If fuel pressure is greater than 66 psi (4.6 kg/cm 2 ) on CSI system or greater than 62 psi (4.4 kg/cm 2 ) on SFI system, go to next step. If fuel pressure is not as specified, go to step 15 . 14. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF . Disconnect engine compartment fuel return line. Attach a flexible hose to fuel return line. Place other end of hose in container. Using scan tool, command fuel pump on and observe fuel pressure within 2 seconds. Fuel pressure should be 60-66 psi (4.2-4.6 kg/cm 2 ) on CSI system and 56-62 psi (4.0-4.4 kg/cm 2 ) on SFI system. If fuel pressure is as specified, go to step 16 . If fuel pressure is not as specified, go to step 17 . 15. Turn ignition on with engine off. Using scan tool, command fuel pump on. Fuel pump should run for 2 seconds. Observe fuel pressure. If fuel pressure is less than 60 psi (4.2 kg/cm 2 ) on CSI system or less than 56 psi (4.0 kg/cm 2 ) on SFI system, go to step 19 . If fuel pressure is not as specified, go to step 30 . 16. Locate and repair restriction in fuel return line. After repairs, go to step 30 . If fuel return line is not restricted, go to next step. 17. Check for restriction in engine fuel return outlet pipe at point where fuel line was disconnected. If fuel return pipe is restricted, go to next step. If fuel return pipe is not restricted, go to step 22 . 18. Replace engine fuel pipes. After repairs, go to step 30 . 19. Inspect in-line fuel filter and fuel line for restriction. If restriction is found, go to next step. If restriction is not found, go to step 21 . 20. Repair or replace in-line fuel filter and fuel line as necessary. After repairs, go to step 30 . 21. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF . Disconnect fuel return pipe union located near fuel filter. Drain remaining fuel from fuel pipes into container. Install appropriate fuel line shutoff valve in place of fuel return pipe union. Open shutoff valve. Using scan tool, command fuel pump on. Bleed air out of fuel pressure gauge into container. DO NOT allow fuel pressure to exceed 75 psi (4.5 kg/cm 2 ). Excess pressure may damage fuel pressure regulator. Slowly close shutoff valve installed on fuel return pipe. Fuel pressure should increase to greater than 66 psi (4.6 kg/cm 2 ) on CSI system or 62 psi (4.4 kg/cm 2 ) on SFI system. If fuel pressure increases as specified, go to next step. If fuel pressure does not increase as specified, go to step 23 . 22. Replace fuel pressure regulator. After repairs, go to step 30 . 23. Check for the following conditions: Low fuel pump voltage due to high resistance connections. High fuel pump voltage due to internal pump binding. Poor fuel pump ground. Partially restricted fuel pump strainer. Incorrect or faulty fuel pump. If any of the listed conditions are present, go to next step. If none of the listed conditions are present, go to step 12 . 24. Repair or replace as necessary. After repairs, go to step 30 . 25. Replace fuel feed line. After repairs, go to step 30 . 26. Start engine and allow it to reach normal operating temperature. Open throttle quickly. Observe fuel pressure. Fuel pressure should increase to near 66 psi (4.6 kg/cm 2 ) on CSI system or 62 psi (4.4 kg/cm 2 ) on SFI system. If fuel pressure increases quickly, see appropriate TROUBLE SHOOTING - NO CODES article. If fuel pressure does not increase quickly, go to next step. 27. Check for the following conditions: In-line fuel filter for restriction. Fuel feed pipe for restriction. Mispositioned or damaged fuel pump strainer. Fuel pump flex pipe for leaks. Vehicle is equipped with correct fuel pump. Fuel pump electrical wiring for high resistance. If any of the listed conditions are present, go to next step. If none of the listed conditions are present, go to step 12 . 28. Repair or replace as necessary. After repairs, go to step 30 . 29. Locate and replace any leaking injector(s). After repairs, go to next step. If all injectors are okay, go to FUEL INJECTOR BALANCE TEST under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. 30. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If additional DTCs are present, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If DTCs are not present, system is okay.
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Saturday, April 18th, 2009 AT 7:35 AM

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