1998 Ford Taurus throttle issues

ARLEER157

MEMBER
1998 FORD TAURUS
6 CYL
FWD
AUTOMATIC
150,000 MILES

I have a 1998 FWD Ford Taurus-SE, 24 Valve DOHC Engine, and have been having throttle issues. When the engine is nice and cool, I can max out the revs and accelerate fully, but as the engine gets hotter, the amount of revs I can reach is reduced until eventually the engine will shut off. My service engine light has been checked multiple times, and is repeating the same code: 1518, Idle air flow controller plunger stuck open. I replaced the idle air flow controller completely, and the problem still happens, along with the check engine light still being on. I spoke to a mechanic about it and he suggested the EGR valve may have gone bad and been causing the idle air flow to stay open. I replaced this a few hours ago, and I'm still having the same throttle problems when it gets hot.

(The car was garaged for two years and has been in running condition for about 2 weeks now, the throttle issues didn't start happening until about a week of driving it again.)

5 Replies

ARLEER157

MEMBER
14 POSTS

Additional note from the original poster: I HAVE cleaned out the openings with carb cleaner, and run it through.

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Tuesday, November 23rd, 2010 AT 7:22 PM

MERLIN2021

MECHANIC
17,250 POSTS

P1518 is not an IAC code! It's a stuck intake manifold runner control, test this way:
15) DTC P1516, P1517, P1518 & P1519
DTCs P1516 and P1517 indicate control circuit failure. DTCs P1518 indicates IMRC stuck open. DTC P1519 indicates IMRC stuck closed. Possible causes are:
? Faulty vacuum hoses.
? Faulty vacuum solenoid.
? Faulty vacuum actuator.
? Cables improperly routed, binding or seized.
? Damaged or disconnected IMRC housing return springs.
? Lever return stop obstructed or bent.
? Lever wide open stop obstructed or bent.
? IMRC actuator cable or gears seized.
On models with electric IMRC system, visually inspect IMRC cables for correct routing. Ensure cable core wire has slack at IMRC housing and stop screw contacts lever. On models with vacuum operated IMRC system, ensure sensor linkage is attached and secure. With engine running, lever must contact closed plate stop screw. On all models, operate IMRC plates while checking for binding and sticking. If any faults are found, repair as necessary. If no faults are found, go to next step.
16) Check IMRC Function

If IMRC is vacuum controlled, start engine and allow to idle for 20 seconds. Turn ignition off. Turn ignition on. Using scan tool, access OUTPUT TEST MODE. Turn all outputs on. When IMRC is commanded on, lever(s) should rotate to full open position. One or both levers should contact wide open stop (one lever being slightly off is acceptable). IRMC levers should cycle fully from closed to open position. If faults are present, go to next step. If no faults are present proceed as follows:
? With DTC P1516 and/or P1517, go to step 64).
? With DTC P1518, go to step 26).
? With DTC P1519, go to step 29).

17) Check IMRC Operation
Start engine and allow to idle. Apply parking brake. Raise engine speed to more than 3500 RPM. When engine speed exceeds 3500 RPM, one or both levers should contact wide open stop (one lever being slightly off is acceptable). When engine speed drops to less than 3000 RPM, one or both levers should contact closed plate stop screw. If levers do not cycle, go to next step. If levers cycle as specified, proceed as follows:
? With DTC P1516 and/or P1517, go to step 64).
? With DTC P1518, go to step 26).
? With DTC P1519, go to step 29).

18) Perform IMRC Mechanical Test
Turn ignition off. Disconnect cables from both left and right intake runners. Operate both levers while checking for binding or sticking. Feel for return spring tension. If any faults are found, repair as necessary. If no faults are found, proceed as follows:
? With DTC P1516 and/or P1517, go to step 64).
? With DTC P1518, go to step 26).
? With DTC P1519, go to step 29).

19) Verify IMRC Circuit Fault
Possible causes are:
? IMRC control circuit open or shorted to PWR GND or SIG RTN.
? VREF circuit open or shorted to IMRC control circuit.
? Faulty IMRC actuator.
? Faulty Powertrain Control Module (PCM).
Turn ignition off. Connect scan tool to Data Link Connector (DLC). Turn ignition on. Using scan tool, select IMRCF PID. If PID value indicates YES, go to next step. If PID value indicates NO, fault is intermittent. Go to step 36).
20) Check IMRC Voltage

Turn ignition off. Disconnect IMRC actuator connector. Turn ignition on. Measure voltage between VPWR terminal at IMRC actuator wiring harness connector and negative battery terminal. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, repair open in VPWR circuit.
21) Check For Open Circuit

Measure voltage between SIG RTN terminal and VPWR terminal at IMRC actuator wiring harness connector. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, repair open in SIG RTN circuit.

22) Check IMRC Circuit Driver For Short To Ground Turn ignition off. Disconnect scan tool from DLC. Measure resistance between IMRC

SIGNAL terminal at IMRC actuator wiring harness connector and negative battery terminal. If resistance is more than 10,000 ohms, go to next step. If resistance is 10,000 ohms or less, go to step 39).

23) Check IMRC Circuit Driver For Short To Ground
Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Connect Breakout Box (014-00950), leaving PCM disconnected. Measure voltage between test pin No. 42 and test pin No. 51 or 103 (PWR GND) at breakout box. If voltage is less than one volt, go to next step. If voltage is one volt or more, repair short circuit.

24) Check IMRC Circuit Driver For Open Circuit
Measure resistance between test pin No. 42 at breakout box and IMRC SIGNAL terminal at IMRC actuator wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in IMRC SIGNAL circuit.

25) Verify PCM IMRC Driver
Reconnect IMRC actuator connector. Turn ignition on. Connect jumper wire between test pin No. 42 and test pin No. 51 or 103 at breakout box. If IMRC plates open, replace PCM. If IMRC plates do not open, replace IMRC actuator.
26) DTC P1518: Check IMRC MONITOR Circuit

DTC P1518 indicates low circuit voltage. Possible causes are:
? IMRC control circuit shorted.
? Faulty IMRC actuator.
? Faulty Powertrain Control Module (PCM).
Connect scan tool to DLC. Ensure IMRC plates are closed. If IMRC plates are open, go to step 20). Turn ignition off. Connect scan tool to Data Link Connector (DLC). Turn ignition on. Using scan tool, select IMRCM PID from PID/DATA monitor menu. If PID voltage is more than 1.6 volts, go to step 34). If PID voltage is 1.6 volts or less, go to next step.
27) Check IMRC Monitor Circuit
Turn ignition off. Disconnect IMRC actuator connector. Turn ignition on. Using scan tool, select IMRCM PID. If PID voltage changed to more than 1.6 volts when IMRC actuator was disconnected, replace IMRC actuator. If PID voltage stayed at less than 1.6 volts, go to next step.
28) Check For Short To Ground
Turn ignition off. Disconnect PCM 104-pin connector. Disconnect scan tool from DLC. Measure resistance between IMRCM terminal at IMRC actuator wiring harness connector and negative battery terminal. Also, measure resistance between IMRCM terminal and SIG RTN terminal at IMRC actuator wiring harness connector. If both resistance readings are more than 10,000 ohms, replace PCM. If any resistance reading is 10,000 ohms or less, repair short to ground in IMRCM circuit.
29) DTC P1519

DTC P1519 indicates IMRC input is greater than expected. Possible causes are:
? IMRC circuit open.
? IMRC circuit shorted to ground or VREF.
? SIG RTN circuit open.
? Faulty IMRC actuator.
? Faulty Powertrain Control Module (PCM).
Turn ignition off. Disconnect IMRC actuator connector. Turn ignition on. Connect jumper wire between IMRCM terminal and SIG RTN terminal at IMRC actuator wiring harness connector. Using scan tool, select IMRCM PID from PID/DATA monitor menu.
NOTE: If scan tool communication error exists, remove jumper wire and go to step 38).
If PID voltage is less than.2 volt, remove jumper wire and go to step 40). If PID voltage is.2 volt or more, remove jumper wire and go to next step.
30) Check For Open In SIG RTN Circuit
Turn ignition off. Disconnect scan tool from DLC. Measure resistance between SIG RTN terminal at IMRC actuator wiring harness connector and negative battery terminal. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in SIG RTN circuit and go to step 33).

31) Check IMRCM Circuit Continuity
Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Connect Breakout Box (014-00950), leaving PCM disconnected. Measure resistance between test pin No. 8 (IMRCM) and IMRCM terminal at IMRC actuator wiring harness connector. If resistance is less than 5 ohms, replace PCM and go to step 33). If resistance is 5 ohms or more, repair open in IMRCM circuit and go to step 33).

32) Check Circuit Operation
Turn ignition off. Reconnect all components. Connect scan tool to Data Link Connector (DLC). Turn ignition on. Using scan tool, access OUTPUT TEST MODE. Access IMRCM and IMRC PIDs. Connect DVOM between test pin No. 8 and test pin No. 51 or 103. Command outputs ON. IMRCM PID reading should be less than 1.6 volts (DVOM reading should be same) and IMRC PID value should indicate ON. If PID values are as specified, fault is intermittent, go to step 34). If PID values are not as specified, replace IMRC actuator and go to next step.

33) IMRC Verification Drive Cycle
Clear PCM memory. Using scan tool, select IMRC PID, IMRCM PID and RPM PID. Test

drive vehicle with transmission in Overdrive. Complete 3 accelerations from a complete stop to a speed requiring engine speed of more than 3500 RPM. Watch for PID values to change. Stop vehicle. Repeat QUICK TEST and retrieve all DTCs. If any DTCs are present, go to appropriate CIRCUIT TEST. If no DTCs are present, testing is complete.

34) Wiggle Test
Turn ignition off. Disconnect IMRC actuator connector. Connect jumper wire between terminals IMRCM and SIG RTN at IMRC actuator wiring harness connector. Turn ignition on. Using scan tool, select IMRCM PID. Observe PID for signs of fault. A fault will be indicated by change in PID voltage from less than.2 volt to more than 1.6 volts. Wiggle wiring harness between IMRC actuator connector and PCM connector. If fault is indicated, isolate fault and repair as necessary. If no faults are indicated, remove jumper wire and go to next step.

35) Wiggle Test
Leave IMRC actuator disconnected. Turn ignition on. Using scan tool, select IMRCM PID. Observe PID for signs of fault. A fault will be indicated by change in PID voltage to less than 1.6 volt. Wiggle wiring harness between IMRC actuator connector and PCM connector. If fault is indicated, isolate fault and repair as necessary. If no faults are indicated, go to CIRCUIT TEST Z.
36) Intermittent Circuit Malfunction

Turn ignition off. Reconnect all components. Connect scan tool to Data Link Connector (DLC). Turn ignition on. Using scan tool, select OUTPUT TEST MODE. Select IMRCM and IMRC PIDs. If scan tool will not allow access to PIDs while in Output Test Mode, install Breakout Box (014-00950). Connect PCM to breakout box. Connect a DVOM between test pin No. 42 and test pin No. 51 or 103 at breakout box. Command outputs ON. IMRC PID should indicate ON and (DVOM should indicate less than one volt) and IMRCM PID should indicate less than 1.6 volts. Observe PID values for signs of fault. A fault will be indicated by sudden change in IMRCM PID voltage or in DVOM voltage reading. Wiggle wiring harness between IMRC actuator connector and PCM connector. If fault is indicated, isolate fault and repair as necessary. If no faults are indicated, go to next step.
37) Check For Intermittent Short To Ground
Turn ignition on. While observing IMRC plates, wiggle wiring harness between IMRC actuator connector and PCM connector. If IMRC plates move while wiggling harness, a possible short to ground in IMRC control circuit is indicated. Isolate fault and repair if necessary. If no faults are indicated, go to CIRCUIT TEST Z.
38) Check For Short To VREF Circuit
Turn ignition. Disconnect IMRC actuator connector. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Connect Breakout Box (014-00950), leaving PCM disconnected. Measure resistance between test pins No. 8 and 90 at breakout box. If resistance is more than 10,000 ohms, replace PCM. If resistance is 10,000 ohms or less, repair short between IMRCM and VREF circuit.

39) Check For Short To Ground
Turn ignition off. Disconnect IMRC actuator connector. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Connect Breakout Box (014-00950), leaving PCM disconnected. Measure resistance between test pin No. 42 and test pin No. 91 (SIG RTN) and 103 (PWR GND) at break. If both resistance readings are more than 10,000 ohms, replace PCM. If any resistance reading is 10,000 ohms or less, repair short to PWR GND or SIG RTN in IMRC control circuit.

40) Check IMRC Circuit
Turn ignition off. Reconnect all components. Connect scan tool to Data Link Connector (DLC). Turn ignition on. Using scan tool, access OUTPUT TEST MODE. Command all outputs ON. Observe IMRC lever(s). If lever(s) cycle open during output command, go to step 32). If levers do not cycle open during output command, go to step 20).
NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 40) to step 64). No test procedures have been omitted.
64) Determine IMRC Fault Path

DTC P1516 or P1517 indicate IMRC plates open or closed time exceeded PCM program. Connect scan tool to Data Link Connector (DLC). Turn ignition on. Using scan tool, select IMRCM PID. Also select IMRC2M PID. If PID voltage is less than 3 volts, go to step 29). If PID voltage is 3 volts or more, go to step 26).

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