Question for the week of September 29th, 1997
What is "fuel cut"?
When the ECU detects a condition that the factory didn't intend the engine to experience, it will try to save the engine using something commonly known as "fuel cut". All of the injectors are shut off as well as all the spark plugs, effectively shutting down the engine. When the condition has passed, the ECU will go back to running spark and fuel as normal. You might experience this as a violent bucking sensation.
What conditions will cause fuel cut?
There are three conditions under which the DSM ECU will chop fuel.
What does fuel cut feel like?
Like you hit a brick wall, if it happens when you have the throttle to the floor. Typically, the ECU thinks too much air is entering the engine, the engine shuts completely off, the air amount decreases to under the limit, and the engine goes back on again. This can be quite jerky.
Some days I get fuel cut, some days I don't, even running a consistent boost pressure.
Fuel cut does not depend on boost pressure - it depends on air flow. Remember the gas laws from high-school chemistry? If you keep the pressure constant, you can pack more of a gas when it is cold into a given space than when it is hot. So even if you keep your boost pressure the same, more air will be flowing into your engine when it is cold at night or in winter than when it is hot during the day or in summer. Thus, you might start experiencing fuel cut at night or during winter that you don't experience at other times.
How can I prevent fuel cut from happening?
Of course, we recommend the Stage II ECU modification, which removes the air flow limit imposed by the ECU. There are other methods that use MAF modifications to "fool" the ECU into thinking less air is entering the engine ("Dime Store Fuelcut Remover", MAF gutting). There is a danger with these "fool-the-computer" mods, however. The ECU might not provide as much fuel as the engine requires - possibly running lean. With our modification, the ECU still knows exactly how much air is entering the engine.
I am getting something that feels like fuel cut, but the car only has a slight hesitation, not a dramatic on/off.
Here are three possible reasons for fuel-cut like hesitation. Keep in mind that none of these involve the ECU directly.
A possible fourth reason for this sort of fuel cut might occur if you have our Stage II fuel cut removal and you are running a modified MAF on a 1st generation DSM. The vortice field that the MAF uses to count the air might be breaking down if there is air disturbance due to honeycomb removal. At this point, you will want to step up to the large MAF used in the Stealth and the 2nd generation DSM. Technomotive will has been running two daily driver cars with a 95 MAF with great results. Look for the 2G MAF upgrade soon.
Past Diagnostic Port issues available.
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