Q: Rough idle when cold

asked by on January 20, 2017

rough idles when cold (30 deg or less). Smooths out once temp is achieved. Has lean bank 1 codes. MAF sensor has been replaced and cleaned. No change.

My car has 180000 miles.
My car has an automatic transmission.

Hello, As a general rule, car engines do not like cold weather and will generally require more fuel in cold operating temperatures. When you start your car in the morning and turn the key to on, the coolant temperature sensor immediately reads the temperature of the coolant and relays this to the computer indicating that the coolant is cold. The computer then knows at this point that it needs to enrich (add more fuel) the air/fuel mixture at startup due to the change in air density. When you start the car, you will notice that it idles high for a period of time until the engine warms up. This is the enrichment cold start process. This is done with what is called a cold start injector which injects more fuel into the motor until the engine reaches a specific operating temperature. The computer simply feeds a little extra gas through the fuel injectors to start the engine and then maintains a certain amount of fuel supply to the motor until it is warm. I would recommend having an expert from YourMechanic come to your location to take a look at your vehicle and diagnose your cold start issue.

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

What others are asking

How do I adjust my 2015 Equinox steering wheel? My leg touches it every time I want to put leg on brakes. I believe I have in high

Hi there. Your steering wheel adjusts so that it can be in the ideal position for you while driving. Adjusting the steering wheel only takes a few seconds: 1. Locate the steering wheel lever, which is to the left of...

Break Pedal Started to make noise when pressing and releasing it

Hello there, a variety of issues will cause noise when the brake pedal is pressed and released on your 2002 Chevrolet Tracker. The most common issues is the pedal return spring, the pedal mount, or the brake pedal rod itself....

2002 GMC Envoy message displayed on message board, turn engine off now. What does this mean?

Hi there. The message could have came on for something that may have been active on the engine or transmission. If the light comes on again, then the computer (ECM) should store the events and you could have them read...

Engine misfire, StabiliTrak wiring problem 2010 Chevrolet Equinox

Hello - these are likely unrelated problems - although all frustrating. The engine misfire will require further diagnosis based on ignition codes. There was likely another problem code - perhaps for an ignition coil or misfiring plugs issue. It is...

ABS light goes on and off when driving at low speeds

The most common cause of the pedal becoming hard is due to the power brake booster failing. The brake booster can cause the ABS faults as well or it could be something different. A qualified technician like one from YourMechanic...

Squeaky noise at the back of the car.

This would need to be heard while driving the vehicle to try and to diagnose if it is a brake or suspension problem. Recommend a qualified mechanic check it out for you.

no spark fire no power to fuel pump computer won't communicate with code reader

Hello, thanks for writing in. When dealing with this kind of situation, you need to start with the simplest options, and work your way down the list. When the electrical power supply is questioned, we need to rule out the...

locks up at high rpm then able to free up and run again

The problem may be the transmission pilot bearing for the transmission input shaft on the back of the crankshaft seizing up or the input shaft on the transmission seizing. If it is not the transmission, then it is the internal...

How do I use the passenger airbag status light?

The passenger airbag status light lets you know whether or not the front passenger airbag is turned on. Your vehicle will automatically detect when there is a passenger in the front passenger seat. When there is a passenger, the airbag...

Related articles

How to Buy a Classic Chevy
For experienced car collectors and rookies alike, owning a classic Chevy is a rite of passage. There are multiple decades and styles in which Chevrolet made popular cars. Many of these cars then had a devout following in the years...
A Buyer’s Guide to the 2012 Chevrolet Cruze
Until Until just the past few years, the Toyota Corolla and the Honda Civic were the kings of the compact car class, and domestic manufacturers had almost nothing in the way of competition for these models. With the 2012 Chevrolet...
How to Get Chevrolet Dealership Certified
Chevrolet car dealerships offer automotive technician jobs to mechanics who are certified through the many training programs available.