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Thread: Rough, miss-like idle

  1. #1
    Join Date
    Feb 2016
    Location
    Cincinnati, OH
    Posts
    157

    Rough, miss-like idle

    After weeks of trying to diagnose a running issue, nothing I have done so far has helped. Actually I feel I've made the issue worse. The car ran "ok" before I messed with it, but not 100%. It would pop on the engine light for a minute or two then go out. Codes said something about the DIS and it going lean. Swapped a DIS, checked IC piping, checked visible vacuum lines for leaks, swapped cam sensor, swapped crank sensor, and swapped coil pack. Still no dice. Replaced the IAC since the center wall was cracked.
    Next thing I will try is replacing the spark plugs and wires. They were an issue before... Other than that, I'm not sure what else I can do other than sell the car.
    Thanks.
    Matthew "Dale" Johnson
    ~"If it looks dumb and works, it's not dumb"

  2. #2
    Join Date
    May 2012
    Location
    Denver Area
    Posts
    827
    How's the outer ring on your harmonic balancer?

  3. #3
    Join Date
    Feb 2016
    Location
    Cincinnati, OH
    Posts
    157

    Harmonic ring

    The outer ring is perfectly ok. No damage to it or play.
    Matthew "Dale" Johnson
    ~"If it looks dumb and works, it's not dumb"

  4. #4
    Join Date
    Dec 2007
    Location
    Salem OR
    Posts
    6,881
    First thing I'd do is stop firing the parts cannon at it.

    Can you re-check and list current codes?

    Have you had a look at the plugs yet?

    Do you have a reliable means of checking fuel pressure?

    When you checked vacuum lines, did you see any raw fuel in the line at the fuel pressure regulator?

    What major work has been done recently?

    How many miles on the fuel injectors?

    Is the engine all stock or are you running mods?

  5. #5
    Join Date
    Apr 2002
    Location
    Norcross, GA
    Posts
    3,323
    You might want to check your O2 sensors, also. A bad O2 sensor can make it run really rough.
    90 5spd, best ever E.T. 12.250
    best ever 1/4mi speed 112.89 mph
    Current dyno tune 383.54 rwhp 418.88 rwt

  6. #6
    Join Date
    Feb 2016
    Location
    Cincinnati, OH
    Posts
    157
    Yeah, not trying to just hang parts on it, just suck at diagnosing.

    -I have not re-checked for codes(have not bought a scanner)

    -was going to check plugs when replacing wires

    -I have an in-car fuel gauge that is quite reliable

    -no fuel in the vacuum line off the regulator

    -there hasn't been any major work to recently. Mid last year was when work was done.

    -I have no idea how many miles are on the injectors. They are 38lb's and the car has about 104,000miles on it with 12,000 on the engine.

    -some mods to the engine. Stage 1 cam, long headers, underdrive pulleys, a/c delete, EGR delete, ported 89 SC w/ 10% pulley and raised top, and a double IC.

    -O2's were replaced mid last year with the other work done.
    Matthew "Dale" Johnson
    ~"If it looks dumb and works, it's not dumb"

  7. #7
    Join Date
    Dec 2007
    Location
    Salem OR
    Posts
    6,881
    Can you get it to a local auto parts store and ask them to read the codes for you?

    I'd like to know more about why you mentioned something about being lean...

    How much vacuum are you seeing at idle?

  8. #8
    Join Date
    Feb 2016
    Location
    Cincinnati, OH
    Posts
    157
    When I checked codes on it a few months back, it gave me a code 19, 41, and 91. As for vacuum, it was about 9-10 on the gauge.
    Last edited by Matt_aka_Dale; 02-12-2019 at 11:54 AM.
    Matthew "Dale" Johnson
    ~"If it looks dumb and works, it's not dumb"

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