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i have a 1996 mercury mystique ls 2.5l dohc

ive had a check engine light on for a while, ive got the pcv vaulve leak fixed, changed the IAC, and ERG valve, Got a new air hose to intake manifold from air housing, a new actuator for the IMRC

now, my last problem....this just wont go away
i know this guy who works for a ford dealership in the service department

i have a code 1506
the guy said its either your Idle Air Control, or the pcm, since i used a autozone IAC he said, get a ford one, so i did, no fix, so now, get a new PCM, and i did, i put it in today and still no fix, the problem is that when i turn the car on with the IAC plugged in the car idles at about 2000 rpm's then when i put the clutch in it will drop to about 900-1000, when i drive and shift from gear to gear, it will stay at about 2000 rpm's untill i let off the clutch. Now, if i disconnect the IAC and run it without, it will turn on and go straight to 800-1000 rpm, and when i drive ill go from gear to gear and it will drop to 800-1000 rpm with the clutch in, when i let off the clutch its a little hard, but thats due to no IAC, the problem is if i leave the IAC unplugged i get a check engine light, I never checked the code but its probably something like, IAC not connected, when i reset my computer and have the IAC plugged in, the car will run high idle, but no check engine light for about 15 miles, then it will come on with the code 1506, which is Idle Air Controller Overspeed error it should'nt do this, expecially since FORD's books' say its either IAC is broke or PCM and both are brand new.....and insight?




Edited by: byran

Hey Bryan,

I just bought a used 1998 Mercury Mystique and I have the same problem with the check engine light too. In my manual it says it either means the 02 sensor needs to be replaced or the fuel cap is not on properly. I tried both and it still doesn't go away, but my car seems to run fine. I hear a lot of people having the same problems with this light too. Hope this helps.

See what I "bolded" below:


Recall ID # 00V367000 - ENGINE AND ENGINE COOLING
<TABLE class=bg_recall_ovrCntr id=closed_36489 style="DISPLAY: none" cellSpacing=0 cellPadding=0>
<T>
<TR>
<TD class=bg_recall_titlecell>Recall Date:</TD>
<TD>NOV 06, 2000</TD></TR>
<TR>
<TD class=bg_recall_titlecell>Component:</TD>
<TD>ENGINE AND ENGINE COOLING</TD></TR>
<TR>
<TD class=bg_recall_titlecell>Model Affected:</TD>
<TD>MYSTIQUE</TD></TR>
<TR>
<TD class=bg_recall_titlecell>Potential Units Affected:</TD>
<TD>262559 Recall Details </TD></TR></T></TABLE>
<DIV class=bg_recall_detailCntr id=open_36489 style="DISPLAY: block">
<DIV>Recall Date:</DIV>NOV 06, 2000


<DIV>Model Affected:</DIV>1995 1996 1997MERCURY MYSTIQUE


<DIV>Summary:</DIV>VEHICLE DESCRIPTION: 1995, 1996 AND 1997PASSENGER VEHICLES EQUIPPED WITH THE 2.0L AND 2.5L ENGINES, AND 1996 VEHICLES EQUIPPED WITH 2.5L ENGINES. TIGHTENING OF THE ENGINE COOLING FAN MOTOR BEARINGS, UP TO AND INCLUDING MOTOR STALL, CAN RESULT IN INCREASED MOTOR TORQUE AND HIGHER THAN NORMAL MOTOR CURRENT AND ACCOMPANYING HIGH MOTOR TEMPERATURES. THIS CONDITION COULD PREVENT THE ENGINE FROM RETURNING TO IDLE.


<DIV>Consequence:</DIV>OVERHEATING OF THE COOLING FAN MOTOR DUE TO EXCESSIVE CURRENT CAN RESULT IN SMOKE AND ODORS FROM BEARING GREASE, INSULATION AND OTHER INTERNAL MOTOR COMPONENTS. IF ELECTRICAL CURRENT CONTINUES TO BE APPLIED TO THE MOTOR, INTERNAL MOTOR COMPONENTS COULD IGNITE POSSIBLY IGNITING OTHER ENGINE COMPARTMENT COMPONENTS.


<DIV>Remedy:</DIV>DEALERS WILL INSTALL A POSITIVE TEMPERATURE COEFFICIENT DEVICE IN-LINE WITH EACH FAN MOTOR. FORD WILL ALSO EXTEND THE WARRANTY ON THE ENGINE COOLING FAN ASSEMBLY TO A TOTAL OF 8 YEARS OF SERVICE OR 100,000 MILES FROM THE WARRANTY START DATE, WHICHEVER OCCURS FIRST. IF THE VEHICLE ALREADY HAS MORE THAN 100,000 MILES, THIS COVERAGE WILL LAST UNTIL JULY 31, 2001.


<DIV>Potential Units Affected:</DIV>262559


<DIV>Notes:</DIV>FORD MOTOR COMPANY 00S44 </DIV>

many times what people forget is that if you reset the computer, you need to start the car and let it learn again for 5-10 minutes. i would clean up the throttle body assembly since something in there might be dirty and hanging up. maybe the passages for the IAC are dirty and or clogged. did you try to clean anything out when changing the IAC?

</>The only thing that made my check engine light go off was resetting my computer.</>
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</>Edited by: dc3886

i had the same problem with mine, i replaced the IAC and O2 and the light and problem went away. might wanna replace the 02 sensor(s). how many miles are on the car? was the o2 sensor(s) replaced before?