1986 Ford Bronco poor acceleration

Tiny
ERICDS30
  • MEMBER
  • 1986 FORD BRONCO
  • V8
  • 4WD
  • AUTOMATIC
  • 200,000 MILES
My Bronco has no power at low RPMs in drive or reverse. Out of gear it idles fine and revs with no heasitation. In drive or reverse it feels like I am starting in a high gear if it was a manual transmition, or like it is cold and the choke is stuck if it had a carb or as if it is missing, when I get over 1500 RPMs it seems to run ok.. I have changed all fluids and filters, plugs wires and cap and roter. We checked the timiing, compression is between 140 & 150 on all cylinders, fuel pressure is at 35 at idle and increased to 45 as the RPMs increased. When we put a vaccume on the EGR it stalled the engine at 10 psi. My code readre gave a code 11 engine off. But the continous codes are 31, 53, 63 and engine running are 34 and 44. Can you help me figure out what needs to be replaced or cleaned?
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Friday, October 30th, 2009 AT 10:45 AM

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Tiny
MERLIN2021
  • EXPERT
Two TPS codes, a secondary air not working code=44, and two EGR related codes. How is the vacuum systm on the truck? Check for vacuum leaks with a can of spray TBI cleaner, spray vac hoses and around the intake manifold, if a leak is found, engine speed will change, usually increase. TPS is tested with an ohm meter. Ford states to test the code 31 first, so lets do that, and see if it cures your problem! Here's how:
TEST K - EGR VALVE POSITION (EVP) & EGR VALVE REGULATOR (EVR) To prevent replacement of good components, be aware that the following non-EEC related area may be at fault: damaged EGR valve. Code 31 Displayed. Turn key off and wait 10 seconds. Disconnect and plug EGR vacuum line at EGR valve. Perform KEY ON/ENGINE RUNNING SELF-TEST . Check for code 31. If code 31 is not displayed, but codes 32 and 34 are, go to step 8). If code 31 is displayed, go to next step. 1. Turn key off and wait 10 seconds. Disconnect and plug EGR vacuum line, then connect vacuum pump to valve. Disconnect harness at EVP sensor. With DVOM on 200,000-ohm scale, measure resistance between EVP signal and VREF at EVP sensor while gradually increasing vacuum to 10 in. Hg. If reading is less than 100 ohms or more than 5500 ohms, replace EVP sensor. Connect vacuum line and harness, then repeat QUICK TEST . If reading does not decrease or valve does not hold vacuum, go to step 13). If reading gradually decreases from no more than 5500 ohms to no less than 100 ohms, go to next step. 2. Turn key on, leaving engine off. Disconnect and plug EGR vacuum line. Disconnect EVP sensor. With DVOM on 20-volt scale, measure voltage between VREF and signal return at EVP connector. If reading is less than 4.0 volts or more than 6.0 volts, go to TEST C - REFERENCE VOLTAGE , step 1). If reading is between 4.0 and 6.0 volts, go to next step. 3. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin 27 and EVP signal at EVP connector. If reading is 5 ohms or more, repair open circuit. Remove breakout box, connect ECA and EVP sensor. Repeat QUICK TEST . If reading is less than 5 ohms, go to next step. 4. With key off, breakout box installed, and ECA and EVP sensor disconnected, set DVOM on 200,000-ohm scale. Measure resistance between test pin 27 and test pins 26 and 46. If any reading is less than 10,000 ohms, repair short circuit. Remove breakout box, connect ECA and EVP sensor. Repeat QUICK TEST . If all readings are 10,000 ohms or more, go to next step. 5. Turn key off and wait 10 seconds. Connect a known good EVP sensor and EGR valve assembly to vacuum and vehicle harness. Remove breakout box and connect ECA. Perform KEY ON/ENGINE OFF SELF-TEST . If code 31 is displayed, replace ECA. Connect original EVP sensor and EGR valve assembly. Repeat QUICK TEST . If code 31 is not displayed, go to next step. 6. Turn key off and wait 10 seconds. Install original EVP sensor on known good EGR valve. Connect EVP sensor. Perform KEY ON/ENGINE OFF SELF-TEST . If code 31 is still displayed, replace ECA. Connect original EVP sensor and EGR valve assembly, then repeat QUICK TEST . If code 31 is not displayed, service exhaust gas recirculation system. 7. Codes 32, 33, or 34 Displayed. Use only VOM/DVOM, not STAR tester, for this step. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale. Connect DVOM negative test lead to STO at SELF-TEST connector, and positive test lead to battery positive terminal. Use a jumper wire to connect STI to signal return at SELF-TEST connector. Perform KEY ON/ENGINE OFF SELF-TEST until end of CONTINUOUS SELF-TEST codes (DVOM reads zero volts). Depress and release throttle. If reading does not go to high voltage, depress throttle to WOT and release. If STO voltage does not go high, go to TEST HH - NO CODES/CODES NOT LISTED , step 15). If reading did change to high voltage, stay in OUTPUT STATE CHECK and go to next step. 8.Turn key on, leaving engine off. Stay in OUTPUT STATE CHECK and set DVOM on 20- volt scale. Connect DVOM to VPWR and EVR signal circuits of EVR. Depress and release throttle several times to cycle output on and off. If solenoid output does not cycle on and off, remove jumper wire and go to step 14). If solenoid output does cycle, stay in OUTPUT STATE CHECK and go to next step. 9. Turn key on, leaving engine off. Stay in OUTPUT STATE CHECK . Disconnect and plug vacuum line from bottom port of EVR solenoid, then connect vacuum pump. Connect vacuum gauge to common output (top) vacuum line to EGR valve. Cycle outputs on and off with throttle. Observe vacuum gauge while maintaining vacuum supply. If vacuum output does not cycle on and off in less than 2 seconds, check and replace EVR filter if obstructed. If filter is okay, replace EVR solenoid assembly. Connect all vacuum lines and repeat QUICK TEST . If vacuum output does cycle on and off in less than 2 seconds, connect all vacuum lines and go to next step. 10. Turn key off and wait 10 seconds. Connect all vacuum lines, and check vacuum lines for proper routing, kinks, cracks, obstructions, leaks, etc. Use vehicle emissions decal as a guide. If vacuum lines are not okay, repair as necessary and repeat QUICK TEST . If vacuum lines are okay, go to next step. 11. With key off, disconnect vehicle harness from EVP sensor. Inspect for and repair any damaged wiring. Set DVOM on 200,000-ohm scale. Disconnect vacuum line at EGR valve and connect vacuum pump to valve. Measure resistance between EVP signal and VREF at EVP sensor while increasing vacuum to 10 in. Hg. If reading decreases gradually from a maximum of 5500 ohms to a minimum of 100 ohms, replace ECA. Connect EVP sensor and EGR vacuum line. Repeat QUICK TEST . If reading does not decrease gradually, go to next step. 12. With key off and EVP sensor harness disconnected, remove EVP sensor from EGR valve. Measure resistance between EVP signal and VREF at EVP sensor while gradually applying pressure to EVP sensor shaft. Look for sudden changes in resistance as shaft is slowly pushed in and released. If readings change smoothly between 5500 ohms and 100 ohms, service exhaust gas recirculation system. Connect EVP sensor and EGR vacuum supply line. Repeat QUICK TEST . If readings change abruptly between 5500 ohms and 100 ohms, replace EVP sensor. Connect harness and EGR vacuum supply line. Repeat QUICK TEST . 13. Turn key off and wait 10 seconds. Disconnect EVR solenoid connector. Set DVOM on 200- ohm scale and measure resistance of EVR solenoid. If reading is less than 30 ohms or more than 70 ohms, replace EVR solenoid assembly. Repeat QUICK TEST . If reading is between 30 and 70 ohms, connect EVR solenoid and go to next step. 14. Disconnect EVR solenoid from harness. Turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between negative battery terminal and VPWR at EVR solenoid connector. If reading is less than 10.5 volts, repair open in harness. Repeat QUICK TEST . If reading is 10.5 volts or more, go to next step. 15. Turn key off and wait 10 seconds. Disconnect EVR solenoid and ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin 52 and EVR signal at EVR solenoid connector. If reading is 5 ohms or more, repair open circuit. Remove breakout box and connect ECA. Repeat QUICK TEST . If reading is less than 5 ohms, go to next step. 16. Turn key off and wait 10 seconds. Leave breakout box installed and ECA disconnected. Set DVOM on 200,000-ohm scale and disconnect EVR solenoid. Measure resistance between test pin 52 and test pins 40, 46, and 60. If any reading is less than 10,000 ohms, repair short to ground. Repeat QUICK TEST . If all readings are 10,000 ohms or more, go to next step. 17.With key off, breakout box installed and ECA disconnected, disconnect EVR solenoid. Set DVOM on 200,000-ohm scale. Measure resistance between test pin 52 and test pins 37 and 57. If any reading is less than 10,000 ohms, repair short circuit. Remove breakout box and connect ECA and EVR solenoid. Repeat QUICK TEST . If code is repeated, replace ECA. If all readings are 10,000 ohms or more, replace ECA. Remove breakout box, connect EVR solenoid and ECA. Repeat QUICK TEST . 18. Code 35 Displayed. This code indicates that engine RPM is too low for correct EGR testing. If code 12 is also displayed, go to TEST X - IDLE SPEED CONTROL (BY-PASS AIR) , step 1). If code 12 is not displayed with code 35, go to next step. 19. Turn key off and wait 10 seconds. Connect tachometer. Perform KEY ON/ENGINE RUNNING SELF-TEST while maintaining a steady 1500 RPM. Record service codes. If code 35 is displayed, replace ECA. Repeat QUICK TEST . If code 35 is not displayed, repair codes as necessary. 20. Continuous Code 31 Displayed. Using CONTINUOUS MONITOR (WIGGLE) TEST , observe VOM or STAR tester LED for indication of fault while doing the following: Connect vacuum pump to EGR valve. Slowly apply 6 in. Hg vacuum to EGR valve, then slowly bleed vacuum and lightly tap EVP sensor. Wiggle EVP sensor connector. If fault is not indicated, go to step 23). If fault is indicated, go to next step. 21. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and connect ECA. Connect DVOM between test pin 27 and test pin 46. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Repeat step 21) and observe DVOM. If fault occurs below 4.25 volts, disconnect EVP sensor connector. Inspect connector and terminals for damage. If connector and terminals are okay, replace EVP sensor. Repeat QUICK TEST . If fault does not occur below 4.25 volts, EGR valve over-shoot may have caused continuous code 31. EVP sensor is good. Go to next step to test harness. 22. Using CONTINUOUS MONITOR (WIGGLE) TEST , shake, bend or wiggle small sections of EEC-IV harness from EVP sensor connector to firewall, and from firewall to ECA. If fault is indicated, isolate fault in wiring and repair as necessary. Repeat QUICK TEST . If no fault is indicated, go to next step. 23. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connector and terminals for obvious damage. If connector and terminals are damaged, repair as necessary. Repeat QUICK TEST . If connector and terminals are okay, fault cannot be duplicated at this time. Continuous code 31 testing is complete 24.


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Saturday, October 31st, 2009 AT 9:09 AM

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