Engine starts spitting and backfiring when driving 55 MPH or more

1995 NISSAN PATHFINDER
250,000 MILES • 3.0L • V6 • 4WD • MANUAL
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TERESA BISHOP
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  • 24 POSTS
i have a problem when accelerating to change gears. it starts spitting and backfiring between 2,000 and 3,000 rpm's. also when driving at 55 mph and above on the highway. we have replaced spark plugs, wires, ignition coil, ignition switch, TPS sensor, MAF sensor, distributor cap. we have checked vacuum lines and EGR system, unplugged the 02 sensor, checked fuel pressure, replaced fuel filter and air filter. engine idles fine. replaced catalytic convertor and muffler. replaced plenum gasket. replaced the ECU. no check engine light.
Oct 25, 2020 at 1:35 PM
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JACOBANDNICKOLAS
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  • 110,175 POSTS
Wow, that's a lot. Can you tell me if it is backfiring through the exhaust or is it through the intake?

I noted that you mentioned the fuel pressure. Can you tell me the pressure reading? Often times a rich fuel mixture will cause a backfire.

Take a look through this link and let me know if it helps:

https://www.2carpros.com/articles/engine-backfires-while-running

Also, if you have a scan tool that has live data ability, please let me know what the short term fuel trims are.

I will watch for your reply.

Take care,
Joe
Oct 25, 2020 at 5:44 PM