If the engine stays cranking for a while without catching, adjust the cranking pulse width setting at the temperature where you’re having this problem. It’s often best to start with what you think is not enough pulse width and add more in, since a flooded engine can take a bit longer to clear. A good rule of thumb to figure out which way to go is to try giving it a little bit of throttle and cranking it. If more throttle makes it easier to start, try less cranking pulse width. If it makes things worse, try more. Note that if you’re seeing zero cranking pulse width, you’ve probably triggered flood clear mode. Check your TPS readings, as having this go too high will shut down the injectors.
If you find you’re not getting anywhere with the throttle test, try pulling a spark plug after a failed start, and see if it’s wet with fuel or dry. If it’s wet, reduce the fueling; if it’s dry, add more fuel to the cranking pulse width.
Next, have a look at what happens after the engine catches. In this case, you’ll want to adjust the afterstart enrichment (ASE) by trial and error to keep the engine from stalling. You can try pulling a spark plug after a failed starting attempt to see if it’s wet with fuel (too much) or dry (too little). Give it whatever combination of ASE and throttle keeps the engine going (not necessarily idling – revving it to 1500 RPM to keep it from stalling can be a good idea on an untuned engine) until it warms up, then dial in the VE table with the engine hot, where ASE and warm up enrichment have shut down. Once you have the final values on these, you can dial in final values for warmup enrichment and ASE.
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Lean idle on hot starts
If the engine runs lean and roughly after hot starts for about a minute or two, then settles to normal, check your air temperature sensor readings. Often, this is caused by sensor heat soak, where the sensor absorbs more heat from the intake manifold than the air does. There are several approaches you can take to fixing this.
- If using a closed element air temperature sensor, switch to an open element type.
- Sensors located in the intake manifold are especially prone to this – try relocating the sensor to the intake piping.
- Use the “Ignore MAT correction during ASE” option to turn off the air density correction for the time when after start enricment is active.
- Adjust the MAT correction curve to add more fuel at high air temperatures.
Too much fuel even with zero cranking pulse width
On some cars with very large injectors, you may find yourself having reduced the cranking pulse width to zero, and the engine is still acting like it has too much fuel. The reason is that the code is adding the injector dead time to the cranking pulse width, and if your dead time setting is high enough, it can be enough pulse width on its own to flood the engine. If this happens, reduce the injector dead time. Note that if you already have a fuel table dialed in, you will need to add more fuel in to compensate.
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