Random misfire on Acura – and seems mysterious

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  • #989572

      1999 Integra LS with 144k miles and Auto, B18B1 – no mods
      Well maintained. Due to the random misfire at idle (car shakes too), did the following still an issue:
      P0300, P0304 and at times P0303 – now all cylinders
      – sparks (OEM), wires (after market)
      – front O2 sensor (OEM)
      – cap & rotors
      – valves adjusted 22k miles ago
      – air filter has 8k
      – cleaned IACV
      – Compression were from 175 to 190
      – Spark plugs did not show any abnormality
      – Swapped ignition coil but no change
      – Batt and Alternator tested fine
      – cold start gave gas smell through exhaust
      – at times smelt gas under the hood but no sign of leaks
      – engine compartment is mostly dry – needed to put new O-ring on Dizzy – the issue started before this repair
      – Lately idle misfire goes away when warms up but happens at 2500rom – then misfires on all Cyl
      – only known issue is the car would need jump start if you don’t drive for 2 weeks & high NOx

      Fuel Trim:
      1500 rpm 2500 rpm
      LTFT 6.2 6.2
      STFT 6.2 8.6

      After I disconnected the battery and let all the Capacitors discharge at idle:
      LTFT – 4.6 4.6
      STFT – 7.8 – 12.5

      Had the car for more than 10 yrs.
      Any help? How can I get Eric to reply?

      Can 87 vs 91 gas or additives cause misfire?

      • This topic was modified 2 years, 11 months ago by ms2000.
      • This topic was modified 2 years, 11 months ago by ms2000.
    Viewing 31 replies (of 31 total)
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    • #990120

        My car passed SMOG despite the potential of P0171 at idle:
        Test 2021-Final → 2021 (prior 2 tests)
        15mph 81 → 357-> 578 (from highest 578 to 81)
        25mph 44 → 1079-> 639 (from highest 1079 to 44)

        This is a 1999 with 144k miles. Emission levels are amazing! These are better than what I had 10yrs ago.
        I still have to figure the Fuel Trim maxing out on idle! I was going to change the IAC but saw some improvement (unsure its lasting improvement) so instead went for the SMOG. I will be pursuing a diagnosis.

      Viewing 31 replies (of 31 total)
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