Skip the auto shop - Our mechanics make house calls

Q: Nonstop backfiring

asked by on

I am replacing a few parts on my truck. DPFE sensor, camshaft position sensor and fan shroud. Since I have to replace the cam sensor I put a socket on the crank shaft and wanted to see if it would move and it did. But I couldn't get to the bolt that holds down the camshaft position sensor because it's behind the engine so I decided to leave it for now. I installed the new DPFE sensor hooked everything back up and went to start the vehicle. It is now backfiring nonstop and even blew the hoses off themes DPFE sensor. So I put the old one back on and it is still backfiring. Did I throw the truck off timing by moving the crankshaft? What could be causing it to backfire this way.

My car has 160000 miles.
My car has a manual transmission.

A: Backfiring occurs when the air fuel charge ...

Backfiring occurs when the air fuel charge in a cylinder(s) fires at the wrong moment often when the exhaust valve is opening. There are backfires into the intake manifold, too, however. If during your work on the engine you moved the distributor, yes, you could have altered the engine timing. However, merely turning the crankshaft, using the harmonic balancer bolt only, clockwise is harmless. The possibility of the ignition timing being off is easy to check with a timing light...just check the basic ignition timing at idle and check the advance function, too.

It is possible that the distributor cap is cracked and/or the plug wires have carbon tracking. In working on the engine, you may have sort of "tipped the balance" on already old, failing parts and set the stage for this backfiring you are getting. Backfiring is also possible is the fuel to air ratio is too high (rich); that means there is too much fuel to create an explosive, fast-burning flame. When too much fuel, the fuel burns slower, and isn’t complete before the exhaust part of the engine cycle. When the exhaust valve opens on the affected cylinder(s), the extra air allows the unburned fuel to explosively burn and the popping noise of a backfire is heard. Check for a dirty air filter by the way which can cause too little airflow. A certified Mechanic can be dispatched to determine the causes of the backfiring in your engine.

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

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

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: My truck keeps giving me the cylinder #8 misfire code

Hello. A continuing misfire on #8 suggests a bad plug wire, a bad spark plug, or possibly oil leaking down onto the #8 plug, shorting it out. Also, if one plug wire is bad, replace them all. Given your mileage,...

Q: Replacement of rear seals

Hi there, thanks for writing in. First, check the surface where the seal rides to see if it is damaging the seal. If it is clean, then you may have bad wheel bearings. The main thing when reinstalling the rear...

Q: Gas pedal sticks

Try and see if the throttle sticks when the engine is not running. If the throttle does not stick, check the throttle plates for carbon buildup. This can cause the plates to stick when it is running. Cleaning off the...

Related articles

Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.