1993 Ford Crown Victoria Strange running after IAC change

Tiny
FORDI6
  • MEMBER
  • 1993 FORD CROWN VICTORIA
  • V8
  • 2WD
  • AUTOMATIC
  • 120,000 MILES
Changed the IAC valve, Now the engine starts, then runs for about twenty seconds almost stalls then picks up again. When cold it almost stops then it seems the computer wakes up and picks the revs up.
Have fitted a new MAF but still getting 157 code.
Strangest part is that when I turn on ignition, no start, the fuel pump runs then stops as normal but after a few seconds it does it again, I can also hear a noise from the regulator.
I'm lost with this one
Do you
have the same problem?
Yes
No
Wednesday, April 7th, 2010 AT 7:23 AM

3 Replies

Tiny
MERLIN2021
  • EXPERT
Did you clear the keep alive memory after you replaced the IAC? You need to do this, and the ECM will relearn idle...Remove negative battery cable for 5 minutes minimum to clear the KAM. Codes 157:
10) Continuous Memory Code 66/157: Check For Intermittent Sensor Failure Continuous Memory Code 66/157 indicates MAF signal was less than 0.4 volt sometime during last 80 warm-up cycles. Possible causes for this fault are: Open MAF circuit. MAF circuit shorted to ground. Faulty MAF sensor. MAF sensor disconnected. Start engine and allow to idle for 5-10 minutes. Perform KOEO SELF-TEST. If Code 66/157 is present, go to step 13). If Code 66/157 is not present, go to next step. 11) Turn ignition off. Disconnect and inspect 60-pin connector at PCM. Service if necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), reconnecting PCM. Connect DVOM between MAF test pin and MAF RTN test pin. See appropriate table at beginning of this CIRCUIT TEST. DVOM should read above 0.4 volt. Start engine and allow to idle. Lightly tap on MAF sensor and wiggle wiring harness to simulate road conditions. If sudden change in DVOM reading occurs, fault is indicated. If fault is indicated, replace MAF sensor and repeat QUICK TEST. If no fault is indicated, leave DVOM connected and go to next step. 12) Check Wiring Harness For Open Or Short Circuit Turn ignition on. Shake and bend small sections of wiring harness starting at MAF sensor and working toward dash panel. Shake and bend small sections of wiring harness starting at dash panel and working toward PCM. If fault is indicated, isolate and repair as necessary. If fault is not indicated, problem is intermittent and cannot be duplicated at this time. 13) Codes 66/157 Or 72/129: Check For Air Leak At MAF Sensor Check for broken or loose air outlet tube clamps at throttle body and air cleaner assembly. Repair or replace as necessary. If no faults are found, go to next step. 14) Check Continuity Of MAF & VPWR Circuit Turn ignition off. Disconnect MAF sensor and PCM wiring harness connector. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between MAF VPWR terminal of MAF sensor wiring harness connector and test pins No. 37 and 57. Measure resistance between MAF terminal of MAF sensor wiring harness connector and test pin No. 50 (Sequential Fuel Injected engines) or test pin No. 14 (except Sequential Fuel Injected engines). If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST. If resistance is less than 5 ohms, go to next step. 15) Check MAF Signal For Short To Ground Turn ignition off. Ensure MAF sensor and PCM wiring harness are disconnected. Measure resistance between test pin No. 50 and test pins No. 9, 40 and 60 (Sequential Fuel Injected engines) or between test pin No. 14 and test pins No. 15, 40 and 60 (except Sequential Fuel Injected engines). If resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If resistance is 10,000 ohms or more, go to next step. 16) Turn ignition off. Ensure MAP sensor and PCM wiring harness connector are disconnected. Measure resistance between PWR GND terminal at MAF sensor wiring harness connector and NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 3) to step 10). No test procedures have been omitted. negative battery terminal. If resistance is 10 ohms or more, repair open PWR GND circuit and repeat QUICK TEST. If resistance is less than 10 ohms, go to next step. 17) Check Continuity Of MAF RTN Circuit Ensure ignition is turned off. Measure resistance between MAF RTN terminal of MAF sensor wiring harness connector and test pin No. 9 (Sequential Fuel Injected engines) or test pin No. 15 (except Sequential Fuel Injected engines). If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST. If resistance is less than 5 ohms, go to next step. 18) Check MAF Circuit For Short To Ground Turn ignition off. Ensure MAF sensor is disconnected. Connect PCM to breakout box. Measure resistance between test pin No. 50 and test pins No. 9, 40 and 60 (Sequential Fuel Injected engines) or between test pin No. 14 and test pins No. 15, 40 and 60 (except Sequential Fuel Injected engines). If resistance is less than 10,000 ohms, replace PCM and repeat QUICK TEST. If resistance is 10,000 ohms or more, go to next step. 19) Check MAF Circuit Output Turn ignition off. Connect MAF sensor wiring harness connector. Start engine. Measure voltage between test pin No. 50 and negative battery terminal (Sequential Fuel Injected engines) or between test pin No. 14 and negative battery terminal (except Sequential Fuel Injected engines). If voltage is .36-1.50 volts, go to next step. If voltage is not .36-1.50 volts, replace MAF sensor and repeat QUICK TEST. 20) With engine running, measure voltage between test pin No. 9 and test pin No. 50 (Sequential Fuel Injected engines) or between test pin No. 14 and test pin No. 15 (except Sequential Fuel Injected engines). If voltage is .36-1.50 volts, replace PCM and repeat QUICK TEST. If voltage is not .36- 1.50 volts, replace MAF sensor and repeat QUICK TEST. 21) Code 56/158 Turn ignition off. Disconnect MAF sensor wiring harness connector. Start engine, and allow it to idle for one minute. Turn ignition off. Repeat KOEO SELF-TEST. If Code 66 or 157 is present, replace MAF sensor and repeat QUICK TEST. If Code 66 or 157 is not present, go to step 22). 22) Check MAF Circuit For Short To VPWR Turn ignition off. Disconnect PCM 60-pin connector, and inspect it for damaged or corroded terminals. Service if necessary. Measure resistance between MAF and VPWR terminals at MAF sensor wiring harness connector. If resistance is 10,000 ohms or more, replace PCM and repeat QUICK TEST. If resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST.
4/7/2010 ...


http://www.2carpros.com/forum/automotive_pictures/62217_MAF_1.jpg



http://www.2carpros.com/forum/automotive_pictures/62217_maf2_1.jpg

Was this
answer
helpful?
Yes
No
Wednesday, April 7th, 2010 AT 12:57 PM
Tiny
FORDI6
  • MEMBER
I did disconnect the battery after the change but I took off the positive not the negative ( would that make any difference)?
From what I see is it crucial that I obtain a "breakout box" If I am to have any chance of fixing problems.
Was this
answer
helpful?
Yes
No
Thursday, April 8th, 2010 AT 7:40 AM
Tiny
MERLIN2021
  • EXPERT
Yes, disconnect the negative cable to erase the codes, removing the positive does kill power but doesn't clear memory, and can cause shorts when reconnecting. ALWAYS disconnect negative to either clear memory, or work on the electrical system! You dont NEED a breakout box, it's nice, but you only need to find the same colored wires at the PCM/ECM connector.
Was this
answer
helpful?
Yes
No
Thursday, April 8th, 2010 AT 12:30 PM

Please login or register to post a reply.

Recommended Guides