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Discussion Starter · #1 · (Edited)
MIL light comes on for days then goes out. OBDII code P1506 IAC overspeed error with MIL not lit. When sitting at a light car misses and gets worse the longer you wait in drive with engine idling. Sounds like a plug misfiring. Formerly had code saying #3 plug misfiring. Different engine but same coilpack. Suspected coil. No DTCs for#3 cylinder now.
Engine is DOHV VIN S and has about 60 K miles on it. Plugs replaced about 2 K miles ago when engine was replaced.
Will pull IAC tomorrow and see if the piston moves and try cleaning it with carb/TB cleaner. Cleaned MAF and TB about a month ago and replaced air filter.

What do you suggest?

BIGHANK :(
 

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I would suggest that you check out the coil pack, if there is even a small hairline crack or one of the boots is gummed up it will misfire and cylinder 3 is usually the most common misfire.
 

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Also clean the TB out.
 

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Discussion Starter · #5 · (Edited)
Removed and cleaned IAC with electrical parts cleaner

Now have MIL light again. Will drive it and see if any difference when heated up and at idle in drive. Replaced with the other IAC that came with used engine. Cleaned both and put other IAC in the manifold. More to follow.

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UPDATE:
As I cleaned both IAC valves I replaced the one giving me the MIL with the original one. Disconnected battery for 5 minutes to clear MIL and restarted the engine wth the original but cleaned IAC. No MIL so far. Will drive car tomorrow and see what happens.
When I tried testing the IACs by turning ignition on and off saw no movement to the solenoid.
Anyone know how to test them?
 

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How does it run when at your foot is to the floor?

verify the tb closes all the way and there is no cable bind.
 

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Discussion Starter · #8 ·
Where is the PCV valve? Have a 24 valve DOHC

i had repeated p1506....pcv valve was junk.
Looked in the shop manuals and online and can't find a PCV valve location.
AutoZone shows a picture of one that looks like a straight thin plastic one.
Where is it located?
 

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PCV is located in the valley of the engine under the intake. It sticks out of a rectangular box, which is the oil seperator. Difficult to see unless you know exactly what you are looking for. Many threads about ways to get the PCV out with minimal effort. Do a search.
 

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Discussion Starter · #10 ·
PCV valve, Ignition Coil and IAC replaced

Finally found the PCV valve and made special tool from 3/4" PVC pipe.
After replacing still ran rough at idle with AC on. Still had misfire codes now on plug 1. Replaced coil. Still rough idling.
Replaced IAC valve. Think that is it. Occasional roughness after sitting at stop in gear with AC on but much different than before. Will see if the car learns new IAC valve and check back in a day or so. Adjusted idle up a little using the screw at the rear of the throttle body. Before replacing PCV was idling at around 900 RPM and harsh going into gear especially clunking into reverse. Lowered idle by loosening screw when had TB off doing PCV. WRONGO. After PCV change idle dropped to abt 550 RPM. Had to readjust screw to put it up to about 600. What should be the idle speed for these Duratecs? This is a 2002 SE wagon.
 

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PCV Tool

Finally found the PCV valve and made special tool from 3/4" PVC pipe.
After replacing still ran rough at idle with AC on. Still had misfire codes now on plug 1. Replaced coil. Still rough idling.
Replaced IAC valve. Think that is it. Occasional roughness after sitting at stop in gear with AC on but much different than before. Will see if the car learns new IAC valve and check back in a day or so. Adjusted idle up a little using the screw at the rear of the throttle body. Before replacing PCV was idling at around 900 RPM and harsh going into gear especially clunking into reverse. Lowered idle by loosening screw when had TB off doing PCV. WRONGO. After PCV change idle dropped to abt 550 RPM. Had to readjust screw to put it up to about 600. What should be the idle speed for these Duratecs? This is a 2002 SE wagon.
For what it is worth.

pic of PCV tool. Out of the tool box.

Idle arout 600 in my '01 DOHC. However the TB should be closed at idle. All the air throught the IAC.

-chart-
 
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