Random Engine Rev's

I was wondering if this is a common issue...or maybe it's normal on newer cars? I've only driven an old beater before the taco.
When I leave the truck in park/neutral for a few minutes, the engine will rev up about 300 revs for about a second or two and then come back down. It's really annoying while trying to eat lunch in my car, but not sure if something like that would do any actual damage.

 

This is a normal characteristic of the truck. I believe the truck has to kick up the RPM's every so often to boost power to the alternator in order to power the AC Compressor or some mumbo jumbo. There was a guy here talking about how it could be re-calibrated or Toyota could just tweak your idle up a couple hundred RPM in order to prevent the dramatic shift.

 

The idle is intentionally kept low to reduce fuel burn, but that leaves it lacking enough amperage for the AC compressor kick in.

 

I have the same thing. It's annoying AF but its "normal" and Toyota wont do anything to fix it because they say thats how it's suppose to behave.

If you turn off the AC it shouldn't do that.

 

That's a lot of new cars not just a Toyota thing. Ford Transit work van does the same stuff. It's just the way it is now.

 

Every car with AC has done that for me but the annoying one is when parking and you turn the wheel, the engine bumps up the rev and the truck slightly lurches. Not enough to overcome the brakes but is bothersome.


J

 

Same here, i have the habit to turn off ac before shutting down car to avoid hearing it at start up while letting the engine warm up.

 

You just confirmed that I'm not crazy! I noticed the lurching months ago and haven't been able to pinpoint the cause of it. I was beginning to think it was all in my head

 

My Truck does not do this at all, with the AC running my Tach Needle is rock solid at around 700 RPMs.

 

At idle turn the wheel a little, if you have any lights on the will dim a bit and the engine will rev a little

 

Normal. Many factors affect the need for more rpm and alternator draw.

 

I messed around with my Car and my Truck, if i turn the steering wheel while sitting the idle drops maybe 100 RPMS, thankfully neither has that surging idle. Starting to wonder if this is something that affects vehicles with Automatic transmissions as mine is Manual.

 

Some common items that will change the idle RPM on ANY vehicle:
Turning the wheels (power steering pump)
Air Conditioning
Turning on lights
Brakes
Cold Start in morning
engaging 4WD
depressing the accelerator pedal.
Using the stereo

All these things put a load on the engine so all these things affect engine RPM. Every single vehicle will do it. Some are just more noticeable.

 

I am aware of that, my responses go back to the OP talking about being in Park and the engine constantly Revving up and down. Mine truck is rock solid at idle and then as Lawfarin suggested I tried cranking the steering wheel around which caused maybe a 100 RPM drop but no surging of any kind.

 

you want bad, go drive a new car that shuts the engine off every time you stop/starts it when you let off the brake... drove a jeep grand cherokee rental that did that. annoying AF.

 

I would never want a vehicle with that Stop/Start crap.

 

Sounds like it would go away with AC off......most cars rev up as AC kicks on and off

 

Yeah but surging to one person is not a big thing to another. My truck has a delta of 200 or so rpm when a.c. compressor is on. No biggie.

 

I think another source is switching from port and direct injection to clean the valves off.

 

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My 1997 Jeep Cherokee used to do that. The Problem was it was never a feature offered by the manufacturer.