Strategies

What were you thinking? That is one question asked a lot, usually after something goes wrong. Lets ask EEC what she was thinking now, before something goes wrong. EEC thinks in a “flow-log,” but humans looking at a flow-log / data table without a degree makes us stare off into space and drool a lot. So it has to be converted into text and broken up into what? Yep strategies! A strategy is the arranging and planning of actions with reference to accomplishing a short-range objective. So we come up with several different strategies and we can accomplish a long-term goal. This is good information for diagnosing and setting up a good Ford EEC EFI system. If you know what she’s (EEC, I make her a “her” some times) thinking you can understand why certain things happen and why certain things don’t.

Like we stated in earlier pages there are basically 11 different strategies, the EEC looks at them all as one, so you will have to imagine those points where one strategy “flows” into another. Try to add the strategies together after you read it once or twice. To start to think like EEC makes one a little off in the head (just ask my family.) So if I start typing sentences that make no sense, just blame EEC for influencing me. EEC’s are like Borgs on Starr Trek, you can try to make them talk like humans, but in the end you’ll be thinking in 1’s, 0’s, Hz, and duty cycles. Don’t get scared, keep reading, this is meant to be read after the sensors, actuators, and the basic EEC page. I’m not going to explain a lot about those parts here, I have to keep this as short as I can for down-loading purposes.

This is the best idea of what the master “Flow-Log” looks like inside EEC that us normal civilians will ever see, or understand. Please don’t send me the typical “my grandma’s ’90 Taurus SHO does this instead, are you stupid,” e-mails just yet. Not all EEC’s are programmed the same, the following is typical logic for typical engines. Some actual numbers and dividing lines could be wrong for some models. And if you read this, thought I was wrong, and know more about this than me; PLEASE e-mail me, I’d love to talk to you on the phone and learn more. Now lets start strategizing.

Start / Crank

This is the start, I know, bad joke. The EEC senses several things to start:

· Power to EEC and fuel pump(s)

· PIP slow and irregular

· MAF/MAP low and irregular

· TPS is closed

· HEGO shows lean

These tell the EEC that you have just checked the dash, want the engine to start, and have turned the key. Even though you’ve heard the fuel pumps whirr, the injectors haven’t released any fuel until it senses engine rotation. Even when the engine does turn over EEC hesitates almost a full second to begin fuel and spark; this is to support oil lubrication. ECT and ACT determine the amount of fuel, the colder it is the more fuel it dumps in. The Throttle Air Bypass is opened 100% to alow for operator error free starting. Spark control is taken over by the TFI, as long as you hold the key in the start position. What if things go bad, your ignition system couldn’t start the engine, and it become flooded? Press the accelerator to the floor while starting, the full open TPS reading will tell the EEC to cut the injectors back to almost nothing. When you decide the fuel has been flushed out release the pedal and the EEC will fire the injectors and the engine fires up. Once the key springs into run, timing is determined by ECT and ACT, the PIP steadies out, the MAF/MAP builds, and the system bumps into the next strategy.

Cold Start & Warm Up

The engine has just started and we have to get adjusted. Well EEC does anyway, this strategy is kind of like you waking up with a hangover next to a stranger. Where’d I set my pants, should I run fast, should I sneak quietly! EEC’s first reaction is to keep the throttle air bypass open 100% or else we’ll be back to engine crank mode. She will drop however, usually to around 1000RPM, then back to base idle as she gets warmer (160°F). EEC looks almost completely at ECT and TPS; both indicate what will occur next. The colder the more fuel gets dumped in and the more timing added. When she gets warmer (about 170°F) she will lean out the mixture. This logic will speed up the time it takes to heat up the engine and converter. Now lets talk about what happens when last nights date wakes up (driver input). If you drive away with ECT under 170°F she jumps to cold drive-away strategy, with ECT greater than 170°F but less than 185°F she jumps into warm drive-away. If you stay asleep and leave everything alone ECT will cross 185°F and we are now in a warm idle. See how confusing it all gets at this point.

BUT don’t be hesitant about driving your car at any time; they wouldn’t make all the strategies if you couldn’t use them. Uncle Sam wants you to drive your car as soon as you start it for economy, cold cars burn more fuel, lets get them warmer quicker! Now hold on Uncle Sam, I recommend a few seconds to ensure oil pressure, and lets hold up on the wide-open throttle assault until we have some nice warm oil for all the internals. Lets all practice common sense and a little love for our vehicles.

Cold Drive-Away

So the TPS and pip are going up, the MAF/MAP is showing greater load, and the ECT is under 170°F. Just for a side note it is almost impossible to draw a dividing line between cold and warm drive-away. But for human comprehension they are separated; don’t ask me why. The TPS and MAF/MAP tell EEC that we are now “driving away.” The goal at this point is to move the vehicle without stalling and warm up the engine as fast as possible. The IAB opens 100% yielding a larger TB and insurance from stalling if the TB slams shut suddenly. We have an enriched mixture that leans out as temp rises. Once ECT is greater than 170F the mixture is actually less than 14:1, this rushes us into normal operating temperatures. After approximately 3 minutes the air diverter moves airflow from the manifolds to the cat. This prevents overheating the manifolds with the enriched fuel ratio. Timing is advanced and retards slowly as temps rise. Once ECT temp has reached the 170’sF we can transfer over to warm drive-away.

Warm Drive-Away

Remember that impossible line from cold to warm drive-away? You can get into warm drive-away strategy one of two ways. First, if the ECT is over 165°F when you drop the trans into gear. Second, cold drive-away passes the command to warm drive-away after ECT crosses 170’sF. Warm drive-away begins life with a lean mixture; remember lean mixtures create a hot harsh combustion chamber. This extra heat will rush us up to normal operating temps faster. Once the ECT temp cross’s 185°F the mixture should return to normal and relate to HEGO signal as long as you aren’t accelerating enough to be in another strategy. The IAB remains at 100% for insurance against stalling. Timing gets pretty tame as fuel is lean and temps are rising. Warm drive-away does include a little EGR function and canister purge activation. Once warm enough for EGR, the timing is advance a little. Exhaust gas dilutes the air making it harder to ignite and less likely to detonate. Once we are warm enough to get EGR function it’s about time to pass command to the “Big-3.” Warm cruise, Part-Throttle, and Full-throttle acceleration can take us down the road from here.

Warm Idle

This one tends to be more about emissions. Warm idle occurs if the engine starts and ECT rises above 185°F, we come up to a stoplight, or place it back into neutral. We now include overheating strategy, where 225°F is the magic number to start complaining. Lets break it down by system. Fuel is now closed loop with HEGO switching. We are now aiming for 14.7:1 A/F ratio for perfect emissions, enrichment will occur only if the ECT is above 225°F. There will be no EGR operation at these RPM’s. Timing is mildly advanced and will begin to retard after a minute. We need hot exhaust gasses to help complete combustion and converter operation. Air is pumped into the converter, but will dump to the atmosphere after several minutes to prevent overheating the converter. The Throttle Air Bypass will be controlling idle, we need a nice smooth idle. Not to high in A/T transmissions to prevent creep at stoplights. Idle will increases 100-200RPM if the ECT or ACT is over 225°F. This RPM increase will help burn the rich mixture cooling the combustion chamber. The faster RPM speeds up the accessories, specifically the water pump and fan. Belt fans will speed up, and electric fans will need more juice from the alternator.

Warm Cruise

We have come to a point where we are happy with our speed and want to just cruise into the sunset. What sounds easy turns out to be one of the most in-depth strategies we use. It is assumed that we citizens spend most of our time at cruise (yeah right), so we need the lowest emissions, highest economy, and moderate power at this time. The only good thing of warm cruise is that engine conditions are stable and need the least amount of safety nets. We still have the throttle air bypass at 100% in preparation for future braking. Fuel is stabilized with the switching of the HEGO, it cycles about 10-20 times a second. To do this the fuel ratio is leaned and enriched slightly each time the HEGO switches from lean to rich. Its like a high wire act, balancing fuel for maximum economy. EGR is operational allowing more timing with less fear of detonation. EGR also lowers the amount of oxygen in the mixture; this means we don’t need as much fuel. The canister purge valve is opened to ingest fuel vapors, this allows us to cut back on fuel metering slightly more and prevents fuel vapors from escaping to the atmosphere. Timing can be advanced to increase engine temperature and counteract EGR influence upon igniting combustion gasses. Timing is used to control engine temps, hotter engines burn fuel more completely. And for the fuel that wasn’t burned in the combustion chamber, we need extra airflow pumped into the exhaust system. This air with the heat of the exhaust creates further break down of HC, CO, and Nox into CO2, H2O, and N2. The catalytic converter can accept all of the airflow without fear of over heating during cruise. The converter is cooled by air passing under the vehicle.

Part-Throttle Acceleration

Unlike full throttle, part throttle makes an environmentally conscience rate of acceleration. The TPS indicates more speed, but not wide-open throttle. If the TPS and acceleration rate causes a downshift, you might get a brief full-throttle acceleration strategy, see below. Fuel remains closed loop, so we can only go mildly rich to stay within HEGO readings. The throttle air bypass remains at 100% incase of sudden braking. Emissions testing have shown that brisk accelerating to a desired speed and cruising makes for cleaner engines. This means that we have to take extra steps in part throttle to help ensure clean emissions. EGR functions reaches its maximum recycling of exhaust gases during part throttle, at most this will be 15% of the incoming air in the intake manifold. Exhaust gas dilutes the air making it harder to ignite and less likely to detonate. This means we can advance the timing more.

Full-Throttle Acceleration

Seat belts on please, this is the master plan, what is the quickest route from point A to point B? Wide-Open throttle assaults of course. The TPS signals wide open throttle to the EEC, this states that the driver doesn’t care about economy or emissions and want maximum power to the rear wheels. Fuel enriches to a set level and richer the colder the ACT is. The timming jumps up around 30°BTDC, and this is where the Knock plays a role. The Knock sensor acts as a safty net for the Ford. The factory does not want the EEC to bump the timing utill we reach that edge. If you buy a new Mustang and add timing with a chip or by twisting the dizzy you could cause detonation. People do this to get more timing and better performance. So the Knock sensor is there to stop the owner that buys a NEW '92 Mustang and twists the dizzy for more performance from blowing a ring or burning some valves. The automatic transmission EEC’s has a worse timing curve during shifts, and the manual transmission EEC’s have worse timming at high RMP. Why you ask? Automatic EEC’s suck out timing during a shift to give the transmission longer life. Manual EEC’s don't have as agressive timing on full throttle just in case you miss a shift and go into melt down. The throttle air bypass remains at 100% giving you a larger throttle inlet and as a back up incase the throttle slams shut. All EGR functions are stopped and the canister purge valve are closed to ensure the exact air to fuel ratios desired. Smog pump air is dumped to atmosphere, air conditioning, electric fan, and all other high demand accessories are shut off to lessen the accessory drive load from A/C and alternator. We also need a rev limiter for the safety of the vehicle; this changes from each model and engine. Basic models are limited to around 6000RPM by cutting back on the injectors. Some Ford engines equipped with factory installed turbo / superchargers include maximum boost control through wastgates.

Deceleration

The vehicle is moving and you lift your foot off the accelerator. EEC sense’s the TPS go to closed and VSS signal slow. This presents a few problems that are easily overcome. First we have to prevent stalling, this is why the IAB has been open, just in case the throttle snaps shut. After throttle closure the Throttle Air Bypass closes slowly closes. Then it controls idle as we reach a stop and move back into warm idle strategy. We are always thinking of emissions and burning fuel as we decelerate is a big waste. EEC turns the injectors almost completely off when RPM is over 1500. Injectors begin operating under 1500RPM or if you hit the skinny peddle. EGR is turned off but the canister purge is opened to burn off fuel vapors from the gas tank. Timing can be advanced for two reasons; first with low airflow signals there is little chance of detonation. Secondly, advanced timing helps push back on the pistons, this helps create that engine brake effect. Engine braking is something diesel owners spend money to increase while EEC is trying its best with gasoline engines.

Failure Mode

Failure mode is an alternate system strategy in the EEC designed to maintain vehicle operation should one or more sensor inputs fail. When a sensor input is perceived to be out-of-limits by the EEC, an alternative strategy will be initiated. Engine running trouble code 98 or 998 will be displayed when failure mode is in effect.

Okay, Ford has a plan for failure, but what is that basic plan? Hot day, cold day, start up, wide open throttle? Well the government has influenced this program. They did not pass a law about failure mode, but Ford doesn’t want to get in trouble either. Emissions are huge part of automotive politics. America wants good emissions during the majority of driving, and Americans want to pass emissions testing. Tests are taken with a warm engine with a moderate load placed one them. The best emissions come from part throttle going down the highway. So the Ford failure replacement values are averaged towards this warm sunny day, with the engine up to normal temperature. Wide-open throttle will produce a lack luster power curve. STARTING is also a big concern, but is it? No, the TFI uses its own timing curve during start, and the stator and TFI tell EEC to dump in the extra fuel. So the engine will still start with the EEC assuming it’s a warm sunny day.

I am going to divide up the sensors into two groups. Ones that will cause failure mode but alow drivability, and the sensors that will cause a no-start or barely drive. Actuators can cause failure mode to take over, but only if the failed actuator is giving a sensor reading way off the chart.

Failure Mode with Drivability	No-start or barely drive*
Air Charge Temp Engine Coolant Temp Oxygen Sensor Heated Exhaust Gas Oxygen Knock Sensor Barometric Pressure Pressure Feedback EGR Delta Pressure Feedback EGR EGR Valve Position	Hall Effect Switch Thick Film Ignition Stator Cylinder Identification Crankshaft Position Variable Reluctant Sensor Manifold Absolute Pressure* Mass Air Flow* Throttle Position*

Limited Operation Strategy

LOS mode is used when the system faults to an extreme, beyond the ability for EEC to act in failure mode. In LOS mode, we have a multi system failure. A faulty ground, blown fuse, or other major incident can cause this. EEC runs in LOS mode so infrequently that Ford thought about dropping it from the programming. In conditions that would cause multiple sensors to fail, there’s a big chance that something else is wrong and it won’t start anyway. There is also the possibility that all software operations have stopped within EEC and she is running on hardware control only. We’re talking huge internal failure, and I’ve already talked on EEC’s durability. There is no set of tables during this condition, EEC runs with one set vales for everything strictly to allow the vehicle to operate until it can be serviced.

This brings us to Ford’s reason to end this program, with this much vehicle damage happing at once, if the vehicle could start, should it? Probably not, the program is set pretty safe for timing and fuel ratios, but there is still a high risk of damage. And that’s all if engine damage hasn’t occurred yet. Newer EEC-V has a whole new set of LOS strategies, some models will not allow engine to operate it oil pressure falls or if the coolant begins to drain out. I personally believe the future will be geared towards safety rather than “limping home.”

Again the engine light will be on when the EEC is operating in Limited Operation Strategy (LOS) modes. The light will stay on for as long as it takes to regain control of the faulty systems.

OVERVIEW OF STRATEGIES

Strategy	Fuel Control	Spark Timing Additions	Emissions	Sensors in Use
1 - Start / Crank	Open loop, 2:1 A/F	TFI controlled	None	PIP / ECT
2 – Cold Start & Warm Up	Open loop, set enrich values	ECT	Air to CAT	PIP / ECT / ACT / NDS
3 – Cold Drive-Away	ECT < 170° = Enrich ECT > 170° = Lean	RPM / Load	Air to CAT	PIP / MAF or MAP/ ECT / ACT / TPS
4- Warm Drive-Away	ECT > 160° = Lean ECT > 185° = Enrich	RPM / ECT / EGR / Load	EGR Can purge Air to CAT	PIP / MAF or MAP/ ECT / ACT / TPS / EGR
5 - Warm Idle	Closed loop, 14.7:1	Retard after 1 minute	Intermittent Air to CAT	PIP / MAF or MAP/ ECT / ACT / TPS / EGR / NDS / HEGO
6 - Warm Cruise	Closed loop, 14.7:1	Approx 30 degrees	EGR Can purge Air to CAT	PIP / MAF or MAP/ ECT / ACT / TPS / EGR / HEGO
7 - Part-Throttle Acceleration	Closed loop, slightly richer than 14.7:1	Load / RPM / ECT / ACT / EGR /	EGR Air to CAT	PIP / MAF or MAP/ ECT / ACT / TPS / EGR / HEGO
8 - Full-Throttle Acceleration	Open loop, set maximum A/F ratio	Set WOT Values or Advance to KS	None	PIP / MAF or MAP/ ECT / ACT / TPS/ KS / VSS
9 – Deceleration	RPM > 1500 = Ø RPM < 1500= 14.7:1	Set Advanced Value	Can purge	PIP / ECT / TPS / VSS
10 –Failure Mode	Open loop set by last ECT signal	Set by last ECT signal and RPM	None	PIP / TPS / MAF or MAP
11 –Limited Operation Strategy	Open loop 14.7:1 from last MAF or MAP signal	Base 10°BTDC	None	PIP

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