Pathfinder runs very rough, backfires.

1997 Nissan Pathfinder initially would not start. When the tow truck driver sat in the vehicle and his weight moved the car up & down, the car started and he backed it onto the tow truck. When the car arrived at the auto shop it would not start again and the tow truck driver set the vehicle at an incline, placed it into neutral and coasted it into a parking space. Again, the vehicle started. He turned it off but it would not restart. The mechanic replaced the distributor ($600.) but after driving 10 miles from the repair shop the car stalled. I was able to restart it but it was running rou
Experienced mechanics share their insights in answering this question :
The most common reason why a car will stop running after a distributor has been replaced is due to the distributor being too loose, causing the vehicle to fall out of correct ignition timing. The misfiring and backfiring issue is a clear indication of something not right with the ignition system. A coil pack, frayed spark plug wire, or fouled spark plug might also be causing this problem.

I think your best bet is to contact a different ASE certified mechanic to inspect your 97 Nissan Pathfinder and diagnose your backfiring problem correctly.

How to Identify and Fix Common car Problems ?

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Backfiring in internal combustion engines occurs outside of the combustion chamber, and is typically the result of an improper air to fuel ratio. An overly lean air-fuel mixture (i.e. an overabundance of air) can lead to a failure to ignite in the combustion chamber, also called a “misfire”.
Common culprits include the ignition control module, plug wires, coils, and spark plugs. Defective Airflow Sensor: A defective airflow sensor can be responsible for a rough idle.
Fuel injector nozzles can become clogged over time, which can lead to a sputtering engine, slow acceleration and the car not having enough power. Fuel injectors can be cleaned if the problem is caught early, but as the conditions worsens, the injectors may have to be replaced.
If too much fuel is added to the engine, it may not all burn up before the exhaust valves open — letting unburned gasoline into the red-hot exhaust headers, where it can combust and lead to a backfire. Too much fuel could be getting into your engine due to damaged and leaking fuel injectors or bad engine sensors.
Backfiring. When your vehicle starts to backfire, a bad ignition coil could be the culprit. A vehicle makes a loud bang sound when unused fuel in the combustion cylinders explodes, causing black smoke to emerge from the exhaust pipe and the strong smell of gas.
Engine Backfires

Backfiring can damage other parts of your car if it`s allowed to continue, so it should always be checked out. But it`s sometimes caused by the ignition coil failing to ignite the fuel in the combustion cycle, and allowing it to infiltrate the exhaust system.

The most common reasons a Nissan Altima has rough idle are a vacuum leak, an issue with the spark plugs, or a problem with the ignition coil.
The common causes for rough running in an engine are: Engine miss. Vacuum leak. Dirty fuel injectors.
Dirty or Worn-Out Spark Plugs

Often, your car shakes when idle simply because it`s time to replace your spark plugs! When yours are dirty or worn out, they fail to fire in the right way. If this happens, they`re unable to ignite the fuel located within each of the piston cylinders on time.

Among the potential underlying causes are vacuum leaks, EGR system malfunctions, malfunctioning oxygen sensors, dirty fuel injectors, fuel pump malfunction, faulty spark plugs, a faulty mass airflow sensor, or a faulty throttle position sensor.
Another possible cause of your backfire is a spark plug refusing to “spark” when the exhaust valve opens. If the air/fuel mixture has become too rich, unburned fuel is left in the exhaust system. The misfired spark plug ignites the rich air/fuel mixture, causing a loud “bang” in the tail pipe.
These sparks can cause fuel to accumulate in the cylinders. As this fuel builds up, it can ignite suddenly and with great force, causing your car to backfire.
Misfires related to fuel system issues are far more noticeable at idle or low-speed driving than they are at highway speeds. A misfire could be caused by not enough fuel getting into your cylinder, leading to an oxygen-heavy explosion.
Worn-out spark plugs or the electrical cables attached to them are one of the most common causes of cars stuttering. A deficient spark plug causes the engine to misfire, making your car jerk when you accelerate.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

01 mustang v6 running rough at idle and drive. Please help. Replaced a bunch, still can’t figure out issue.
ANSWER : This may be a sign of a faulty MAP sensor as the vehicle responds adversely to a load put on the motor (i.e. putting it in gear, turning on AC or engaging the brakes). The Manifold Absolute Pressure (MAP) sensor senses engine load and generates a signal that is proportional to the amount of vacuum in the intake manifold. The engine computer then uses this information to adjust ignition timing and fuel enrichment. When the engine is working hard, intake vacuum drops as the throttle opens wide. The engine takes in more air, which requires more fuel to keep the air/fuel ratio in balance. When the computer reads a heavy load signal from the MAP sensor, it adjusts the fuel mixture to slightly more rich than normal so the engine can produce more power. The computer will then retard (back off) ignition timing slightly to prevent detonation that can damage the engine and decrease performance. This may also be caused by other closely related components such as a dirty or failing mass air-flow sensor, a faulty throttle position sensor or potentially a vacuum leak. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.

Vehicle started running rough while driving. Now running/idling rough running rich.
ANSWER : Hello. From the symptoms you describe, it would appear that your vehicle is having issues with the oxygen sensors. P0172 is the code for bank 1 being too rich. This can be caused by a wide variety of issues. The other two codes are for the sensors on bank 2, having excessively high voltage.

This may be due to the rich condition, faulty oxygen sensors, or faulty wiring. The black smoke and soot is a result of excessive fuel that is not being properly burned, and exiting the tailpipe as smoke. A few common causes for these symptoms are a bad fuel pump, fuel pressure regulator, or engine management sensor. As engine management systems can sometimes be difficult to diagnose, I would recommend having the rough idling issue inspected by a professional technician.

The truck intermittently, has a very rough idle, and runs rough,usually after warming up.
ANSWER : Hello. This can be caused by a number of different things. If this occurred right after you had gotten fuel then I would start by testing the fuel pressure. I would do this when the vehicle starts running poorly. It is possible that the bad fuel contaminated the fuel pump and it is not putting out the right pressure. If the fuel pressure is fine then I would check the other sensors readings with a scan tool. One other common thing that I have seen on this engine is a leaking intake manifold gasket. It starts leaking on the bottom side and that leak causes the MAF and MAP to not read correctly which causes it to run like this. If you would like to have this rough running condition looked at, consider having a YourMechanic certified techniciancan come to your home or office to diagnose why it is running rough.

Truck is running rough, loses power, backfiring noise – 1994 Nissan D21
ANSWER : Hey there. I would check fuel pump output and condition of fuel injectors (flow rate and solenoid resistance). After that, I would evaluate the ignition system, including distributor, plug wires, timing. If you would like to have this checked for you, a certified technician from YourMechanic can come to your car’s location to inspect the loss of power symptoms and help get your car back in running shape.

Hi i have a 2003 impala…it runs rough and backfiring after i put bad gas in it…
ANSWER : If the rough running started virtually "instantly" after you bought the gas, of course bad gas is a possibility. You might ask the station if they received reports from other customers. If they did, drain the tank for sure and make a claim. Of course it is always possible that the purchase of gas and the malfunction are just a coincidence. To get expert advice and get the cause of the problem identified, you can request a rough running diagnostic. If the responding certified mechanic recommends draining the tank, he or she can do that. If the issue turns out to not be fuel related, an ordinary rough running diagnostic would be performed to identify the problem. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

Cranks and runs rough have to keep foot in gas to keep running. Has new fuel pump and died while driving after pump was changed
ANSWER : Check fuel pressure. There are only three possible explanations: a fault in fuel supply (plugged filter, injectors, etc.); ignition system problems; and air induction including the idle air control valve, throttle position sensor, mass air flow sensor and vacuum leaks including the PCV and EGR systems. If obvious, and easy to check, possibilities do not reveal the fault, the recommended service to request is a rough running diagnostic and the responding certified mechanic will travel right to your location and get this diagnosed and resolved for you. It is also possible that diagnostic trouble codes have set and the mechanic will attempt to retrieve those using an appropriate scan tool. If you have further questions or concerns, do not hesitate to re-contact YourMechanic.

Car is running roughly at around 45 mph
ANSWER : Hello. It is possible that all of the spark plugs and spark plug wires need to be replaced in order to fix the problem on your Plymouth Grand Voyager. Also, if carbon has built up in your intake, throttle body, and EGR valve parts, this may cause the problem you are experiencing. Having the throttle body cleaned as and a fuel induction service may help as well. Have a certified technician, such as one from YourMechanic, come and assist you with diagnosis and repair of your car’s rough running at high speeds.

replaced bad coil pack and new coil not sparking car starts but runs rough engine light on blinks sometimes
ANSWER : Hello and thank you for your questions. If your engine was rebuilt about 10 months ago, the question is to determine if the management system has been installed as well. With the symptoms that you are having, it sounds like the coil packs are old and in need of replace. You replaced numbers 1 and 4 and now number 6 is not firing. I recommend replacing number 6, 2, 3, and 5. This will ensure that you have all 6 coil packs that are new.

Just because the coil packs are okay during a test doesn’t mean that they are functioning correctly. Coil packs on Buick vehicles from 1998 – 2005 last between 150,000 to 200,000 miles. I also recommend having your fuel injection system flushed. Unless you have new injectors, the old injectors could cause a cylinder to fail, even though it is working correctly. These symptoms can cause the engine to have a rough idle and rough running during conditions. If you need assistance troubleshooting the rough running condition, I recommend having a professional, like one from YourMechanic, inspect the car and move forward with repairs.