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96 Nissan Pathfinder - Missing/Hesitation/Bad Idle
Howdy folks. 96 Nissan Pathfinder. 3.3L V6 2WD. 151K on the odom. Three
weeks ago started getting a real bad surging/poor acceleration problem. At a stop, the engine would idle poorly, and on acceleration, would be very sluggish, and then suddenly accelerate as if nothing was wrong. So, this is what I ended up changing: Fuel pump, all fuel lines (rubber), fuel filter, under hood fuel hoses, fuel pressure regulator. New Plenum gasket. New Throttle Position Sensor. All new vacuum lines under hood that I could reach or replace. New spark plugs. New rotor. Cap and wires have less than 5K on them. Both front O2 Sensors (Denso). So the surging/poor acceleration is gone. But here is the problem that remains. When the engine is cold, it starts and runs perfect. As it warms up, everything is ok. After about 10-15 mins of driving I start getting a bad miss between 40 and 50 mph, real evident on cruise control. The engine appears to be "hesitating". Here is the kicker. Disconnecting both front O2 sensors makes the problem go away. Both sensors are brand new Denso, OEM style replacements. I can run all day with the O2 sensors unplugged (at the under hood wiring harness) and the engine runs perfect. Plug them back and I get: Cold engine: Good running engine Hot engine: Missing, stuttering, hesitation. What is the problem? Dirty fuel injectors? I have never cleaned the injectors. Bad O2 grounds? Help! |
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"Not Anyone We Know" > wrote in message nk.net... > Howdy folks. 96 Nissan Pathfinder. 3.3L V6 2WD. 151K on the odom. Three > > So the surging/poor acceleration is gone. But here is the problem that > remains. When the engine is cold, it starts and runs perfect. As it warms > up, everything is ok. After about 10-15 mins of driving I start getting a > bad miss between 40 and 50 mph, real evident on cruise control. The engine > appears to be "hesitating". Here is the kicker. Disconnecting both front > O2 sensors makes the problem go away. Both sensors are brand new Denso, OEM > style replacements. > > I can run all day with the O2 sensors unplugged (at the under hood wiring > harness) and the engine runs perfect. Plug them back and I get: > > Cold engine: Good running engine > Hot engine: Missing, stuttering, hesitation. > > What is the problem? You probably have a vacuum leak. When the O2 sensors are unplugged the computer sees a major fault and runs it rich. I would guess if you went through an emissions check it would be exceeding HC. When it's hot the O2 sensors allow the computer to lean it down, and due to your vacuum leak it's getting way too lean. Ted |
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