Discussion
This is a clip from KFM's Esprit fact file.
Consult the fact file, KFM, or someone with knowledge about the mem-cal.
Some owners of multi-port fuel injected Esprits have suffered problems with engine stalls when downshifting of lifting off the throttle. The problem appears to be caused by the software in the ECM.
The ECM uses the Throttle Position Sensor (TPS) to determine how long to keep the injectors open for. When you take your foot off the throttle (as in a "coasting-down" condition), the ECM shuts off fuel delivery to the engine as a method of improving fuel economy. At this point, it is the wheels (via the transmission, clutch and flywheel) combined with the forward momentum of the car that are actually making the engine spin. During these conditions, the ECM shuts down the ignition because there is no fuel to burn. When you press in the clutch pedal, you disconnect the link between the wheels and the engine. The engine RPMs start to drop because the throttle is still closed. Usually, the ECM should detect this condition and start fuel delivery and ignition again to bring the engine speed back to idle. If this happens as it's supposed to, the engine will kick in again as the RPMs are making their way back down to the 1000RPM idle speed. If for some reason, the ECM takes too long to kick the ignition and fuel delivery back on, the RPMs will drop below the idle speed and will surge back up once it kicks in. If it takes a little longer, the engine stalls because the RPMs drop to zero and now you need to use the starter or the drive wheels to get the engine spinning again. The ECM uses vehicle speed (via the Vehicle Speed Sensor - VSS), engine speed (via the Flywheel Sensor), and throttle position (via the TPS ) to determine when to turn on or off the ignition and fuel delivery. The question is why is it taking so long to start them back up again. I don't have an answer for that one yet, but I do have a solution. Lotus has issued a software upgrade for the S4s ECM especially to take of this problem. Owners of the Esprit SE can also take advantage of this upgrade and "slightly" improve the performance of their cars at the same time. The repair involves removing the ECM's MemCal cartridge and having it reprogrammed. You may have an older S4s chip and need to have it upgraded by either Sanj or Andy.
Calvin
Consult the fact file, KFM, or someone with knowledge about the mem-cal.
Some owners of multi-port fuel injected Esprits have suffered problems with engine stalls when downshifting of lifting off the throttle. The problem appears to be caused by the software in the ECM.
The ECM uses the Throttle Position Sensor (TPS) to determine how long to keep the injectors open for. When you take your foot off the throttle (as in a "coasting-down" condition), the ECM shuts off fuel delivery to the engine as a method of improving fuel economy. At this point, it is the wheels (via the transmission, clutch and flywheel) combined with the forward momentum of the car that are actually making the engine spin. During these conditions, the ECM shuts down the ignition because there is no fuel to burn. When you press in the clutch pedal, you disconnect the link between the wheels and the engine. The engine RPMs start to drop because the throttle is still closed. Usually, the ECM should detect this condition and start fuel delivery and ignition again to bring the engine speed back to idle. If this happens as it's supposed to, the engine will kick in again as the RPMs are making their way back down to the 1000RPM idle speed. If for some reason, the ECM takes too long to kick the ignition and fuel delivery back on, the RPMs will drop below the idle speed and will surge back up once it kicks in. If it takes a little longer, the engine stalls because the RPMs drop to zero and now you need to use the starter or the drive wheels to get the engine spinning again. The ECM uses vehicle speed (via the Vehicle Speed Sensor - VSS), engine speed (via the Flywheel Sensor), and throttle position (via the TPS ) to determine when to turn on or off the ignition and fuel delivery. The question is why is it taking so long to start them back up again. I don't have an answer for that one yet, but I do have a solution. Lotus has issued a software upgrade for the S4s ECM especially to take of this problem. Owners of the Esprit SE can also take advantage of this upgrade and "slightly" improve the performance of their cars at the same time. The repair involves removing the ECM's MemCal cartridge and having it reprogrammed. You may have an older S4s chip and need to have it upgraded by either Sanj or Andy.
Calvin
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