Some of you know the types of threads/posts I usually get involved with, and may have noticed that a great number, have to do with EEC-IV problems...."read the codes"...."suggest to run a set of KOEO/KOER self-tests"...."measure resistance from pin x at sensor connector to pin z at ECM connector....LUK"......reads familiar?

In those posts, I usually use a lot of tech articles or write-ups links that don't necessarily have 100% correct information......but they save me from doing a lot of typing . I thought it would be a good idea to start a mythology type of thread, to be updated as information and members share their information. Soooo.....let's start with the first one:

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Resources used for the "Mythology Conclussions"...courtesy of http://fordfuelinjection.com and http://www.veryuseful.com/mustang/tech/engine/ :
1. Electronic Fuel Injection (SFI-MA) Strategy Book - Strategy Level "GUFB"
2. Tom Clouds: eectch98
3. Tom Clouds: eectch97
4. Mustang 5.0L & 4.6L TPS FAQ, By stangPlus2Birds
5. EEC-IV Inner Workings By T. Moss
6. Datastream Parameters Observations on EEC-IV Systems (non-Mustang EEC-IV and Mustang '95 w/Datastream Capabilities)

Mythology Case #1:
Setting the TPS as close to .99 vdc will give you better performance.

Fact #1:
Eventhough the TPS is a variable position resistor, the EEC-IV logic only cares about the following:

- Minimum voltage at closed throttle over .49 vdc. , less than .49 and codes 23 and 63 will set as failures.
- Max voltage closed throttle should not exceeed 1.2 vdc, or codes 23 & 53 will set as failures.
- Closed throttle TPS value is reset by the system to the lowest value read when ignition is turned on.
- A voltage increase of .04 vdc from the minimum registered to id part throttle status.
- Minimum WOT value of 3.2 vdc and not higher than actual Voltage REFerence (VREF) generated by the ECM.

The above means that eventhough the TPS varies voltage, the system only uses it to establish 3 states. Closed Throttle, Part Throttle and WOT by the voltage min-max values to set a code, minimum to determine WOT (=2.71 vdc over minimum closed throttle setting), and by monitoring TPS voltage change to determine acceleration/steady/deceleration status...among other sensors inputs like the MAF and VSS.

Based on the specified working range of the TPS by the EEC-IV system below:


The normal setting for a TPS @closed throttle, would be between .7 vdc and 1.0 vdc, allowing a .2 vdc window up or down for variance caused by thermal stress and charging system variability.
So....if your closed throttle TPS signal voltage falls within .7 vdc and 1.0 vdc.....no need to adjust or elongate screw holes to set it to .9999 vdc.

NEXT!

Mythology Case #2:
VSS Sensor is only used for the Cruise Control System

Fact #2:
The computer uses VSS input to operate the following:

1. The idle air control valve
2. The canister purge system
3. The torque converter clutch (SN95 Mustangs w/AODE/4R70W trannys)
4. Cruise control
5. Distance traveled
6. Deceleration

VSS input in the EEC-IV is also used to arrange and set idle strategy while shifting/deceleration/stopping via the "dashpot" control mode and prevent deceleration stalls. If you complain about stalling, hanging idle, surges when coming to a stop or between shifts....make sure you don't have a code 29: Insufficient input from vehicle speed sensor, and if this is a MAF conversion, make sure the VSS connection to pins 3 & 6 in the ECM are done.



The minimum value required by the system, to switch to VSS "dashpot" strategy is 5 MPH for EEC-IV systems and 3 MPH for EEC-V's. Why do MAF checking tables use a relationship between MAF output and vehicle speed?



It has to do with load/acceleration/deceleration calculations the EEC-IV uses VSS input for.

NEXT!

Mythology Case #3:
EGR deletion w/out deleting its function in the EEC-IV logic, will cause engine pre-detonation (pinging) at part-throttle.

Fact #3:
This is a special case, mainly because it would only be true under the following condition:

-----> EGR gases are blocked from entering the intake, but the EGR valve is set to operate so the EGR Valve Position (EVP) sensor related codes are not registered. No other EGR system related codes registered, and system operational (valve opening/closing portion).<-----

Deletions by:

1. Placing resistors in the EVP connector to simulate closed position EVP value and prevent code 31 (EVP circuit below minimum voltage of 0.24 volts.) from getting logged....but having EVP not opening codes registered (33 & 34).

2. Removal of EGR Valve Regulator (EVR) solenoid, vacuum lines, EGR valve and EVP sensor, thus getting EGR system codes logged in the system...

3. Having an EGR failure code present in the system, IS a way of deleting the EGR function from the system.....

DO NOT cause engine pre-detonation problems due to the EGR delete......Why???????

The EEC-IV logic DOES NOT allow the operation of the EGR system when an EGR failure code is present. Therefore, no timing advance is added by the system, since the EGR function is cancelled/bypassed.

Timing table compensation for EGR operation works as follows:

A. When an EGR code is not registered (EGR Failure Flag=0).
B. Advance degrees added to compensate for EGR opening, are calculated by the EEC-IV based on the actual position change of the EVP sensor...the wider it's opened, and bigger the load, more advance timing is added to the ignition timing table....if the EVP sensor voltage change = 0 from its closed position.....0° advance is the added timing to the tables.

Bottom line....if engine pre-detonation is experienced after an EGR delete, with the only exception mentioned......it's not caused by the EGR being deleted....need to check A/F, total timing advance and combustion chambers for carbon deposits.......etc.

BTW....if you have an EGR code currently set in the system as an On Demand or KOER code....you already have the EGR deleted!

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so.... if you put on one of those egr eliminator/ simulators
there should'nt be any problems egr related?

Nope...no problems at all .........even if you don't put one of the eliminators...only difference would be that the CEL might light up, but the fact that the EGR will stay bypassed will remain.

cool deal. i want to get one of those soon

FWIW....all you have to do is plug the vacuum line at the EGR valve, as long as the EVP is within specs closed position...that's it!...now, if you want to remove the valve.....you'll need the resistors pack.

Mythology Case #4:
Increasing fuel pressure will raise HP

Fact #4:
The amount of fuel added to the engine is calculated by the system based on engine conditions, and the feedback from the sensors in the system, including the O2's. A/F target is 14.64:1 and the ECM will make adjustments to the Injector Pulse Width (IPW) to reach the A/F stoichiometry goal.

EEC-IV tables are used for the calculations for IPW, including adaptive strategy learned for open loop and close loop operation, the only difference is, that once the system achieves close loop state, adaptive tables are updated....they are used under open loop, but not updated......like turning adaptive strategy off.

Fuel pressure setting does have an effect in the system since the amount of fuel will vary at the same IPW, the higher the pressure, more fuel is delivered at the same IPW setting....the system will get the feedback of this condition (O2 readings), and will trigger an IPW re-calc (shorten it) to reach A/F goal, thus cancelling the effect of a higher pressure setting at a point. However, fuel pressure setting IS important, since....


From: EEC-IV ADAPTIVE CONTROL - YOUR BEST FRIEND OR YOUR WORST NIGHTMARE! By: Mike Wesley
......and confirmed in EEC-IV setups with the datastream capabilities, watching "fuel trim" parameter while causing (or troubleshooting) extremely rich/lean conditions.

Fuel pressure setting has a "centering" effect of the ECM fuel trimming capabilites or limitations....EEC-IV has the capability of doing short and long term "fuel trims" within a 25% (+ or -) of its internal fuel tables. This means that it can either increase or decrease fuel trim given the real time conditions (short term) and the new center fuel trim (long term or adaptive learned).

Let's use an example.......if long term fuel trim is "learned" and set at +15% by the system, and you suddenly get a vacuum leak that requires a 13% fuel trim "addition", the system will be uncapable of compensating for it and lean codes will show up.....on the other hand,......... if you have the long term fuel trim at -5%, ......the system will compensate for the time the condition is present, w/out the lean codes showing up, since the correction trim required is within its pulse width compensation range limitation.

Keep in mind, that the system will continue to update long term trim, and raise its value (in close loop), ....if the vacuum leak is permanent, long term will reposition to +8% with time....leaving less "room" to add fuel when required due to..........other conditions.

How to ensure fuel pressure increase is in control for richer WOT runs?.....old EFI school trick for drag racing....increase fuel pressure, disconnect O2 sensors to force open loop and prevent adaptive strategy from updating tables, clear Keep Alive Memory (KAM) and adaptive strategy learned.....you're set until O2's are reconnected and O2 codes cleared.

NEXT!

Thanks to TENGRAM for bringing this "Mythology Case" to the table in a previous thread on the subject.

Mythology Case #5:
Code 67 (Neutral safety circuit failure) is OK to have as a failure code in the EEC-IV system. It does not affect anything.

Fact #4:
The neutral safety circuit for manual tranny setups, is comprised by to switches, clutch sense switch and a gear/neutral safety switch on the tranny, setup in a parallel circuit as shown below. The clutch sense switch is open pedal up, and the gear switch is open in any gear other than neutral.



As explained in Myth case #2, regarding the VSS and the "dashpot" logic in the EEC-IV for idle control....the neutral switches circuit, also have an influence in the EEC-IV calculations for the operation of the IAC valve, by helping identifying engine conditions and selecting the proper Idle Speed Control (ISC) strategy. Their input, or state, is used in the VSS/ISC dashpot calculations to identify engine operation conditions (accelerating/decellerating/cruise mode/closed loop idle modes), and prevent idle problems (stalls and surging, hanging idle).

Idle variations are more noticeable (and traceable) in Ford's EEC-V (OBD-II) systems, I worked on a case in a '02 V6 Mustang, where idle would hang above 1,200 RPM's, as long as the VSS input was of 3 MPH or more, and the clutch pedal was pressed, EEC-V followed a "shifting gears" strategy, that kept idle high....this is normal....no OBD-II failure codes were registered by the system. Eventhough this was an OBD-II case, the strategy used by the system is similar to/based on the EEC-IV's.

So.....when you're working on an idle problem with your EEC-IV Fox or SN95, make sure codes 67 and 29 are taken care of, and not present as On Demand, Continous Memory or Engine Running failure codes.

NEXT!......

Mythology Case #6:
Check Engine Light (CEL) or Malfunction Indicator Light (MIL) is not turning on in the instrument panel, there are no codes registered in the EEC-IV.

Fact #4:
The EEC-IV system CEL/MIL strategy is used by the system to let the driver know there is a failure present that is causing the system to use an alternate strategy to set A/F and timing. The strategy usually known as "limp mode" is called Failure Mode Effects Management (FMEM), and is one alternate strategy, among others, used by the system to compensate for failures.

The EEC-IV components that will cause the CEL indicator to illuminate, when a failure condition is present are:

¤ Air Charge Temperature (ACT) sensor

- Code 24: ACT input out of self-test range of .3vdc - 3.7vdc
- Code 54: ACT input greater than self-test maximum of 4.6vdc
- Code 64: ACT input less than self-test minimum of .2vdc
¤ Barometric Pressure (BP) sensor/Manifold Absolute Pressure (MAP) sensor

- Code 22: BP/MAP out of self-test range of 122.4 Hz - 162.4 Hz
¤ Engine Coolant Temperature (ECT) sensor

- Code 21: ECT input out of self-test range of .3vdc - 3.5vdc
- Code 51: ECT input greater than self-test maximum of 4.6vdc
- Code 61: ECT input less than self-test minimum of .2vdc
¤ Throttle Position Sensor (TPS)

- Code 23: TPS input out of self-test range of .49vdc - 1.22vdc closed throttle
- Code 53: TPS input greater than self-test range of 4.84vdc
- Code 63: TPS input less than self-test minimum of .39vdc
¤ EGR Valve Position (EVP) sensor

- Code 31: EVP input is below minimum voltage of .2vdc
- Code 32: EVP voltage is below closed limit of .29vdc
- Code 34: EVP voltage is above closed limit of .67vdc
- Code 35: EVP circuit is above maximum voltage of 4.81vdc
¤ Hard Failure Code 98 present

- MAF code 66: Mass Air Flow sensor is below self-test minimum of .4vdc
- MAF code 56: MAF sensor input is greater than self-test maximum
- MAF code 26: MAF sensor input not in range of .2vdc - 1.5vdc engine running

As you can see, there is a BIG list of EEC-IV codes that will not cause the CEL/MIL to illuminate (12, 13, 14, 15, 18, ..........and the list goes on), but they will cause driveability problems, lack of power, idle control issues, stalls, etc, etc....without you knowing about their existence in the system, if a KOEO/KOER self-test combo is not performed.

So make sure you do run a DIY KOEO/KOER self-tests to check for codes, don't assume a "no codes" present condition because the CEL/MIL indicator does not turn on in the instrument panel....or, let the symptoms be your guide...

NEXT!.......