explanation of B3 ecm/ecu.

[jawbraeka]

Can someone please explain what the ecm/ecu is for for a carbed Ford Festiva please? I've been looking around for an answer and can't find one at all. as far as I've gathered, its to do with the ignition and some electrical systems as well as sensory systems, but specifically what would they are has got me stumped.. can someone clarify what they would be? I'm specifically wanting to know for a 1.3 litre carburettored motor as I also understand that ECM/ECU has to do with the efi also in some regards too.

Can someone please clarify exactly what it does for a carburettored vs efi car please and if there is Also some difference between manual and automatic, please explain that too.

Thanks.

[bravekozak]

Unfortunately, you have a feedback carby. The Feedback carburetor Actuator modifies the air fuel ratio in the idle and primary main metering systems according to computed signals received from various engine sources, primarily exhaust gas oxygen content. A stepper motor operates an air bleed control valve that varies air bleed into the fuel.

My personal recommendation is to swap in a Weber/Escort carby instead.

Since you are in Australia, you may even consider adapting the single carb model from a KB laser. Be sure to get him to throw in air cleaner too for the $65. Post lots of pics if you decide to do the swap.

[KingFish]

On a Carbed car the ECM controls the carb. The Festiva uses a 'feedback' style carb, meaning sensors provide inputs to the ECM that uses programmed strategies to control outputs, i.e. vacumme and electronic solenoids to change the characteristic of the carb with the intentions of decreasing emissions form the tailpipe and increasing fuel economy and drive ability The strategies can get real complicated real quick and I have never bother to learn them. The ECM is not used in the control of ignition in a carbed car as far as I am aware. If you change over to a early 1.6L Escort carb, you can eliminate the ECM altogether. The ignition is controlled by the ignitor in the distributor or on the strut tower depending on your car.

The EFI cars use the ECM to control most functions of the engine and cannot be eliminated unless you opt for a aftermarket ECM like a StratifiedAuto PnP or a MegaSquirt you build yourself.

[KingFish]

Damn you spell check, you slowed me down!!

[denguy]

Great info. Thanks guys. I bet the techs ran for cover when a carbed Festy pulled into the dealership.

[FB71]

Great info. Thanks guys. I bet the techs ran for cover when a carbed Festy pulled into the dealership.

nope, not all of us! I used to love feedback carbed cars!

[Safety Guy]

Jim wrote:

"nope, not all of us! I used to love feedback carbed cars!"

Jim loves him some feedback carbs! I heard he really loves it when they spit fuel back in his face!

Karl

[Movin]

^^ it is the carb cleaner from cans, used when checking to make sure a passage is open..
and not noticing the other end is pointing at your face..
Its kind of like bear spray, you recover eventually!!

Back to OP I believe the ecu shuts off idle fuel during decel
to reduce back fire in exhaust and clean emissions during
decel.