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.

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?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Car engine revs way up immediately upon starting engine.

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: front end vibrates when in park and at stop lights

Hello there, many faults will cause your 2008 Mazda 3 to have a vibration at idle. The most common would be a misfire condition, fuel pump, vacuum leak, oxygen sensor, mass air flow sensor, or a coil. A qualified Technician...

Q: The mechanics is saying to change the Brake pads and engine mount replacement cost $550. is this worth to repair the car or sell

You have an "older" car but one with relatively low mileage on the engine. (My car is 26 years old, so don't feel bad). The big issue with "older" cars is corrosion and deterioration of critical rubber products like valve...

Q: Loud clicking noise sound like something is about to blow up less power then usual

You may have blown out one of the spark plugs on the cylinder head. It would cause a misfire and noise like air escaping every time the cylinder should fire. I suggest having a certified mechanic, like one from YourMechanic,...

Related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
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...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...