Q: Nonstop backfiring

asked by on November 05, 2016

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.

Engine is backfiring Inspection $94.99 - $114.99 Get a Quote

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.

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


Experienced Mechanic?

Earn up to $70/hr

What others are asking

Can't shift out of Park
The shift mechanism has a solenoid that is part of the mechanism, which may have broken the small lever that releases the lock that enables the shifter to get out of Park. The fix is to replace the shifter assembly....
Water leaking into car
Water leaks can come from various sources: a clogged drain tube in the AC/Heater box can cause overflow through the heater vent, or faulty cowling can cause water ingress into the passenger compartment. With the battery disconnected, water needs to...
Car's rpm goes up and down while idling.
The power train control module controls the idle on the vehicle using different sensors and actuators. If you do not have any codes in the computer for the problem then you may have to have the computer reprogrammed per the...
Difficulty starting 1992 Volvo 740 when the engine warms up
The fuel pressure on your 1992 Volvo 749 should be checked to make sure it is within proper specifications. If there is a clog or malfunction in the fuel system, the car may experience a poor running situation or may...
Won't turn over. No crank.
If the alternator quite working, this will mean the battery is likely discharged, which would be a normal condition when an alternator fails. The starting system uses ten times the current of every other electrical system on the car. It...
Can i drive my truck with a small leak from the oil pan gasket
Hi There, Unfortunately, an oil leak from the oil pan is the area of the motor with the largest capacity of oil. A leak from this area can quickly go from very minor to very major with little time to...
AC Thermostat
Hi there. Check the thermostat on the air conditioning system and see if its freezing up again by shutting off the vehicle and letting it sit for about 30 minutes. If you see frost on the evaporator, then the system...
Leaking fluid AND sometimes won't start right away.
Hi there. Typically a 'coolant leak' and a hard starting problem is not related. However, coolant should be mixed at a ratio of 50 percent coolant and 50 percent distilled water. Adding water instead can thin the mix, crack the...
How likely would all 4 tires lose 8 pounds of pressure each at the same time when just a week before they were fine?
Tire pressure changes 1 PSI (up or down) for every 10 degree change in ambient temperature so temperature differences would not account for a large 8 PSI drop. The only other possibilities are leakage through the valve core and at...

Related articles

The Best Used Cars to Buy If You Just Had a Baby
Having Having a baby will completely change your life. Your activities and hobbies will change. Your sleeping patterns will change. Chances are good that you’ll also be looking for a change in vehicles. You need to ensure that your car...
Symptoms of a Bad or Failing Fuel Pump
Common signs include a whining noise, hard starting, engine performance issues, and an inability to start the car.
How to Find the Keyless Code on a Ford Explorer or Mercury Mountaineer
Many Many Ford Explorers and Mercury Mountaineers were manufactured with an option known as the Ford keyless entry keypad. Some models refer to it as SecuriCode as well. It is a five-button numeric keypad that is used to: Eliminate fumbling...