Skip the auto shop - Our mechanics make house calls

Q: Car engine revs way up immediately upon starting engine.

asked by on

When starting the engine, it sounds like you have your foot pressed to the floor on the gas pedal as soon as you start it, without even having your foot on the gas. Then it idles down, but then sometimes that idle is rough, or loping.

My car has 226000 miles.
My car has an automatic transmission.

A: Common causes of high RPM excursion at star...

Common causes of high RPM excursion at start-up are typically: large vacuum leak, throttle plate stuck open, cruise control stepper motor stuck in one position; faulty throttle position sensor, and/or faulty idle air control motor or solenoid. If you request a diagnostic by a certified YourMechanic technician, he or she would first check to see if any Diagnostic Trouble Codes have been set. If no codes were set, the technician would go through the referenced possibilities until the root cause of the high idle is found. Once the idle excursion is resolved, the rough running condition would be evaluated. The causes of rough idle "slightly" overlap the problem areas cited above but there are lots of additional causes such as faulty fuel and ignition system components and, of course, mechanical problems such as uneven cylinder compression, burnt valves and so forth. If you desire to set up a diagnostic to resolve both the high idle and rough running condition, please schedule with YourMechanic.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
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

Q: Code P0171. Do I need to take car to dealership to address this problem.

Hey there. It sounds like your throttle body is bad. Check to make sure it's clean and not sticking. Clean the throttle body if necessary and check for loose connections with the throttle body connectors, too. Since you said that...

Q: Car chokes after starting

There are two options for the engine for your car. They are both 3.0 v6’s that are vastly different. If you are talking about oil in the spark plug tubes on the DOHC v6, that indicates a bad valve cover...

Q: I accidentally put oil in my coolant tank, what can I do? 1998 Mercury Marquis

Hello - not ideal, but certainly not fatal. You may even be able to remove the coolant reservoir, and drain the coolant/oil mix before any has gotten into the engine. Even if oil is in the coolant, a coolant drain,...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...