When going at the desired speed (say 40mph) and there is lots of coasting room, I just let go off the accelerator and the car basically coasts. The engine RPM drops from 1600-1800 down to 900-1000 and it actually can coast a long way. Sometimes, I need to go faster (if I’m initially started at a slower speed) and when I press the gas pedal slightly, the tachometer shows the engine rpm jumps from the coasting 900-1000 to 1600-1800.
Is the tachometer (add on by ScanGuage) reporting it correctly? Is this a bad form of acceleration for the engine?
If you’re going the desired speed and you let go of the accelerator, the car will eventually slow down, and then you’ll have to get on the accelerator again.
I just looked at the scangauge website. The tachometer should be accurate, since it is seeing the same rpms that the PCM is seeing
I believe you’ll eventually revert to “normal” driving
This sounds like relatively conservative (and proper) driving to me, and is waaaaaay gentler than any mechanical stress levels you would need to worry about. It doesn’t even sound like the transmission is downshifting to a lower gear, which is good. You don’t need to worry until the engine RPM is close to 6000 for this car… you sound like a driver who will rarely exceed 3000 (thanks for that :-).
Letme give another scenario…If I’m going the desired speed and I let go off the accelerator…the RPMs drop to 1000 from 2000. If after a few seconds (the car is still going at the same speed…hasn’t slowed down), I press the gas pedal again (at the same pressure level)…the RPMs show 2000 (same as before). Is this bad for the engine?
Yeah, I never exceed 3000, try to keep it around 2500 when merging and 1000-1600 for normal driving. This is not for MPG…but I want to keep my engine for 1 million miles
At 40 mph, your torque converter is not locking up, assuming that your car has a lockup torque converter. At 55-60 mph, you should be running about 2400 rpm and it would not change as much when you let up at the torque converter would be locked up, but you would feel more drag.
BTW, it isn’t doing any harm as you describe it now.
Million miles, lofty ambition. I drove my Saturn 100 miles a day commuting to work and back and a couple cross country trips, in 9 years, I racked up almost a quarter million. It would have taken me about 40 years to reach a million miles at that rate.
The engine isn’t the only thing on the car that should be cared about. Your engine acceleration is so OK that you don’t have to worry about it for 200,000 miles. Steady engine speeds will make it last much longer, even more than 300,000 miles. After that, luck is involved.
Unsteady engine speeds will prevent the O2 sensor from doing useful work, like making the computer find the right fuel/air mixture. A more even speed will help out your catalytic converters and they cost money too. You shouldn’t coast and then accelerate when you can do a steady speed. You only coast when there is a stop coming up. Coasting to a stop will save you some fuel.
Lastly: There’s nothing wrong with having a few squirrels running around in your head. Just try to keep them from chewing up the wiring.
