Q: Reving

asked by on January 23, 2018

How come when the truck is in park or neutral and I tap the gas it will rev up to 3000 rpm and then back down slow, but it doesn’t do it in reverse or drive

When the car is in gear, the load on the engine is sufficient to prevent the malfunction. If the engine idle speed on your vehicle is controlled by an idle control valve (ICV), that ICV valve can fail or a faulty or blown fuse in other electronically controlled systems can cause the IAC motor to malfunction, leading to a higher than normal engine idle speed. Failures in the ICV valve itself are often due to excessive carbon buildup in the intake manifold. Other possible causes of the excursion in RPM you are describing include vacuum leaks, a malfunctioning throttle and, rarely, a PCM/ECM malfunction. With regard to vacuum leaks, on a fuel injected engine a vacuum leak will cause high engine idle as the engine’s oxygen sensor detect the extra oxygen entering the engine through the vacuum leak. The newly lean (too much air relative to fuel) status will result in the engine’s computer pumping in additional fuel, resulting in an abnormally high idle. A malfunctioning throttle system can cause both a high idle as well as an engine stall. A dirty air intake or cracked air intake tube is often the culprit. If you desire that this high idle problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, please request an engine idle speed diagnostic - high idle and the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

My car cuts off once it gets hot and there's white smoke

It is very possible that you could have an oil leak from your valve cover gasket. If this happens this oil can land on the exhaust and burn away causing the white smoke you are seeing. I would recommend having...

Metal-on-metal sound coming from front driver's side brake.

Hello, brakes being one the most important systems on the car, this should be handled sooner rather than later and the vehicle should not be driven. I am unclear as to why you believe the caliper should have been replaced....

I changed the coil pack spark plugs and plug wires my car still runs bad why

If the engine is running bad then you should be getting a code set in the computer. If not, then a scanner should be used to view data to see if the engine is running lean or rich. Check the...

Related articles

The Best Used Cars to Buy If You're a General Contractor
If If you're a general contractor, you probably aren’t in the market for a used car. More likely, you’re looking for a pickup truck, because you need to haul equipment and supplies to various job sites. Most contractors will likely...
2012 Chevrolet Silverado vs. 2012 Dodge Ram: Which One Should I Buy?
When you are looking for a way to get a load of mulch or gravel, or need to haul a large trailer or boat behind your vehicle, chances are you are looking for a truck. Trucks are not meant to...
Ten Sports Cars That Double as Good Daily Drivers
The best daily driver is a car that's reliable, usable, and still fun to drive. Popular daily sports cars include the BMW M3, Subaru WRX, and VW GTI.