Q: Car idling rough and missing.

asked by on January 13, 2016

My car is idling roughly and missing. It could be one of many things: the spark plugs, rotor cap, plug wires, or the throttle body could need cleaning, I am not sure.

Car idle is rough Inspection $79.99 - $89.99 Get a Quote

A misfire will generally cause a rough idle, but you must find out if its one cylinder misfiring or a random misfire, this is were a scan tool is essential. If you can trace the misfire to one cylinder its usually a coil pack or injector but if its a random cylinder misfire your looking at air/ fuel delivery, vacuum leaks, dirty mass airflow sensor, "lazy" 02 sensor that doesn’t respond fast enough, or a fuel pump thats on its way out. Have a mechanic like one from YourMechanic check for codes and look at the real time engine data while its running.

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

Throttle body need replacement or not?

Hi there. Option C is best; have YourMechanic come to your location and complete a check engine light inspection first before replacing any components. This will allow them to determine if the throttle body itself is the source and needs...

My speedometer does not work

The speedometer is controlled by the PCM (Powertrain Control Module). The PCM receives data from the ABS module then sends it to the instrument cluster. In all, there are three modules, and a VSS (Vehicle Speed Sensor) involved with the...

My car battery is dying while it's parked. I replaced the battery and in just a week it died while sitting parked overnight.

Hi there. There could be a parasitic load on the battery causing it to drain overnight. To check this symptom perform the following: Remove the negative battery cable (-) Get a digital meter and put one lead on the...

Oil pressure drops too low and then when I start the drive it goes back up to normal 2002 Mercury Mountaineer

Hello - low oil pressure at a hot idle is a normal indicator of worn engine bearings in a high-mileage engine. Since the oil light turns off when you accelerate indicates the oil pump is pumping more than 5 psi...

How do I adjust the sound system clock?

It only takes a few steps to adjust the clock in your vehicle’s sound system: 1. Press and hold the Clock button until the clock flashes. 2. Use the Seek/Track buttons to adjust the hour. 3. Use the Tune/Fast Forward-Rewind...

Car jumping and trying to stall when started

There are many possibilities that could cause your concern. The most likely cause would be one of the engine sensors not reading correctly. If the computer isn't getting the right info, the engine may not be able to continue running...

EPC warning light is illuminated

Hi there. The EPC stands for Electronic Power Control. This light comes on when there is a problem with the engine. In some vehicles, the EPC limits the amount of throttle that can be used so that the engine is...

I have no codes but when in park car idles up and down and allready changed tps

You need to have the engine idle relearned by disconnecting the battery for two minutes and then starting and idle engine in park and then drive for two minutes each and then do same with a/c on and blower on...

Does the Mechanic verify the replacement part I think I need is what a actually need?

If you call out a mechanic to install a part that was diagnosed by another company then to answer your question is no. The mechanic that is to install a previously diagnosed parts cannot in most cases verify the part...

Related articles

How to Troubleshoot a Clutch Pedal Sticking to the Floor
Clutch pedals in manual cars stay on the floor if there's a failed clutch release bearing, slave cylinder, clutch master cylinder, or clutch linkage.
How to Troubleshoot a Car That is Hard to Start
"Car not starting" is a common complaint among car owners and is caused by faulty car batteries, spark plugs, car starter, or fuel pump.
The Best Tool to Diagnose Sensor Failures
Mechanics may regularly run into sensor failures when performing a repair service. Automotive oscilloscopes help properly diagnose these issues.