Random misfire on Acura – and seems mysterious

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This topic contains 31 replies, has 2 voices, and was last updated by ms2000 ms2000 1 year, 11 months ago.

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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 ago by ms2000 .
    • This topic was modified 2 years ago by ms2000 .
Viewing 31 replies (of 31 total)
  • Author
  • #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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