Q: Truck is back-firing.

asked by on February 13, 2017

After changing the harmonic balancer my truck was running rough. I asked the friend that did the work what he suggested, he said a tune-up. He then performed a tune-up on the truck and now it is back-firing. He doesn't know why. I asked if he adjusted the timing (thought this was done after a tune up, not sure) he said he didn't touch the timing. Please help.
My car has an automatic transmission.

There are a few possible causes for an engine to backfire. Some of the more common causes are a vacuum leak, lean condition caused by a weak fuel pump, an exhaust manifold leak, or a faulty ignition system. With the information that you’ve provided, in that the engine was running rough before doing the tune up, I would focus on either the ignition system, or the fuel system. With the backfiring showing up after the tune up, I would suspect that there has been a pair of wires crossed when they were reinstalled after replacing the plugs. This is a very common occurrence, and even the best in the business do it from time to time. With the engine running rough before the tune up, I would look more at the ignition coil, the wires, and check the fuel pressure. If you feel you could use some help identifying and/or repairing the problem, contact a certified mechanic, like those available at YourMechanic.com.

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

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

Truck cuts off when stopping

Hello. Stalling at stops can be caused by many things. A few common causes are: faulty idle air control valve vacuum leak fuel or engine management issue The most common of these is a failed idle air...

When I give my car gas and let off it keeps throttling up by itself, I changed the tps sensor no help

In the majority of vehicles, engine idle speed is controlled by an idle control valve (ICV). The ICV valve can fail or a faulty or blown fuse in other electronically controlled systems can cause the IAC motor to malfunction, leading...

I am upgrading the suspension on my 2009 dodge charger sxt do I need to upgrade the rack and pinion as well

Hi Natasha. Thanks for contacting us tonight. Anytime you make an aftermarket adjustment to suspension, you should always make corresponding changes to the steering system as well - as they work together and both impact suspension alignment. It's best to...

Related articles

The Best Used Cars to Buy If You Don’t Have Kids
Buying Buying a used car is rarely a simple process, but if you don’t have kids, you have many more options than those who have to account for additional passengers. There are plenty of choices out there, depending on your...
The Best Used Cars to Buy If You're a General Contractor
If If you're a general contractor, you probably aren’t in the market for a used car. More likely, you’re looking for a pickup truck, because you need to haul equipment and supplies to various job sites. Most contractors will likely...
Top 10 Best-Selling Cars of 2016
Ford F-series pickup trucks, Toyota Camry, and Honda Civic are some of the best-selling cars of 2016 and all deliver on reliability and efficiency.