Ford Thudnerbird LX 3.8 liter Codes 411 and 412

Hi Group/Experts:
I am reposting some data on my older T-bird after fixing some previous problems and finding time to work on it again.

I posted about a year ago with some hesitation problems and othe OBD I codes.

I am getting Codes 411 and 412, here is the work and tesinug I have recentnly accomplished:

1 Retimed engine to exactly 10 degrees BTDC with SPOUT connector disconnected
2 Replaced upper and lower intake manifold gaskets and checked for leakage __> all good
3 Checked all the vacuum hoses for leaks and proper routing ,
4 Replaced the IAC valve on the throttle body after ALLdata steered my to this with atest of pulling the IAC harness and seeing if the idle dropped about 100 RPMs. --> mine did not do anything when removed
5 Checked all fuel injectors for proper resistance --> all within spec
6 New Battery
7 New distributor after finding the new one I replaced last year had the #1 post turned 180 degrees around so that the round part was facing the rotor
8 New spark plugs/wires rotor/cap installed last year with little driving done between then and now
Other issues I found:
9 Re-Checked all spark plug gaps


Other issues i found while working on car:

1. While timing found that the spark would miss every coupla blinks on #1 cylinder using an inductive timing light (I originally thought this was due to the defective distributor cap but still doing ti with the new one
2. when removing the harnes from the New IAC, RPMs still do not drop by 100
3. the timing does not seem to change whether spout shorting bar is removed or not
4. No Check Engine light or hard codes since replaciung the IAC but only monitored while idling no driving (I was getting some prior to replacement but they were intermittant while driving and the light would go off. Usually happened during decleration or static cruising but no during aggressive throttle.)
5. I notice a lag in throttle response when I snap it on very quick, it seems to lag a split second


ALLData Excerps:

Diagnostic Trouble Code (DTC) 411 indicates that during Engine Running Self-Test, engine rpm could not be controlled within the Self-Test lower limit band.

Possible causes:



Improper idle air flow set. ??
Vacuum leaks. --> Checked
Throttle linkage binding. --> not binding
Throttle plates open. --> not open
Improper ignition timing. --> timed
Idle Air Control (IAC) solenoid contamination. New
IAC circuit short to ground. ?? don't have a breakoiut box
Damaged IAC solenoid. --> new
Does engine Idle speed appear normal? --> about 850-900
Yes -- Remove IAC solenoid and Inspect for contamination. If contamination is present, determine if solenoid is a type that can be cleaned.

If Diagnostic Trouble Code (DTC) /symptom is still present, replace IAC solenoid.



No -- Reset idle airflow to specification. Refer to Fuel Delivery and Air Induction for idle airflow adjust procedure. If unable to reset idle to specification, go to KE16. See: KE16 - Check For Condition Affecting Idle

DTC P0412:

Diagnostic Trouble Code (DTC) 412 indicates that during Engine Running Self-Test, engine rpm could not be controlled within the Self-Test upper limit band.

Possible causes:



Open or shorted circuit.
Throttle linkage binding.
Improper idle airflow set.
Idle Air Control (IAC) solenoid contamination.
Items external to Idle Air Control system that could affect engine rpm.
Damaged IAC solenoid.
Damaged Powertrain Control Module (PCM) .
Key "OFF".
Connect engine tachometer.
Start engine.
Disconnect IAC harness connector.
Does rpm drop or stall?
Yes -- Go to KE2. See: KE2 - Check For Other DTCs
No -- Go to KE3. See: KE3 - Check For Other DTCs


could this be my EGR circuit? I am gonna test this tonite

What would cause a missing timing strobe every couple of seconds?

How about the coil? Gonna also check R tonite.