Skip the auto shop - Our mechanics make house calls

Q: Misfires at idle

asked by on

I have a relatively new truck that's idling rough. If I'm sitting still, it stays at around 500 rpms, but every few seconds the needle dips and goes back up. I've been to the dealership several times, but they keep telling me it's normal. I have another chevy truck that doesn't do this. One line they're feeding me is that the engine deliberately misfires one cylinder while it's idling to do some sort of diagnostic check every few seconds. Is that true? If not, what else can you suggest as a cuprit?

A: Hello. This engine does do a series of self...

Hello. This engine does do a series of self-tests, but you should not feel them. Since the idle is so low, I typically check the throttle body as it may be defective since the vehicle is still so new. If that is fine then I would typically start by reprogramming the vehicle's computer. If the problem is very subtle, then it is normal. If it is very well-pronounced, then you need to get GM's service center involved if the dealer is not helping you with this, as your car should still be under warranty. Alternatively, a technician from YourMechanic can diagnose your engine's misfire and determine exactly what needs to be repaired for you.

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・Save up to 30%

Get a quote

What others are asking

Q: Problems with battery draining for no 'obvious' reasons.

Your problem could be a module staying on or a faulty relay. If you have an alarm installed, they can sometimes drain a battery when engaged. The parasitic drain you are experiencing can be diagnosed by a certified technician that...

Q: CEL purge valve manifold

Hello there, thank you for asking about your 2011 Mercedes-Benz C63 AMG. If you are suspicious, you may want to hire another facility for a second opinion. Each time the Check Engine Light was illuminated, there's a good chance the...

Q: Stalling and misfiring at idle on a 1999 BMW Z3

Those things are notorious for getting vacuum leaks on them because the tops of the engines are all made out of plastic--including the intake system. Especially on the driver's side, there are all kinds of plastic piping. You'd want to...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
How to Renew Your Car Registration in Oklahoma(DELETED)
Having your car registered with the Oklahoma Tax Commission is an important part of driving legally in this state. You will need to do this within 30 days of moving to Oklahoma...
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...