Rough Idle, Hesistation on Throttle

Discussion in 'Workshop Forum' started by Conda, Dec 2, 2019.

  1. Conda

    Conda Daily Driver

    Hey everyone. Got a chance to mess with the X1/9 a bit today and got it fired up to only find that its now a sputter-y thing.

    I went around the engine removing and plugging vacuum lines and it had no positive effect on the idle when removed, all did make it worse. So I'm thinking it isn't a basic vacuum leak.

    After shutting it off and thinking a bit, going out to start it again it was very insistent on having the throttle pressed to fire and start and took a couple tries to do so. After "warm" starting it was once again sputtering and I took this video of it.

    Anyway, I'm gonna drag it into the garage and have at it, anyone got suggestions about what to examine first? Thanks all.

    edit Forgot to mention that this is a 1987 X1/9 with FI on a 1.5L. Timing belt was done within the last 6 months along with fuel pump/filter.
    Last edited: Dec 2, 2019
  2. aarpcard

    aarpcard True Classic

    First two things I would do would be to make sure the ignition timing is correct and make sure the TPS is adjusted correctly.

    Also probably a good idea to run through the whole FI troubleshooting manual too.
    Last edited: Dec 2, 2019
  3. Conda

    Conda Daily Driver

    Ignition timing looks great, fired it up and had absolutely no issues. Idled evenly. Thinking its an issue that may come and go with temp or moisture.

    Decided to have at cleaning the intake assembly to give me something to do. I have the Air flow meter along with the auxiliary air valve off of the car now.

    What is the process for cleaning these two? Generic intake cleaner? Should i take the lid off of the air flow meter and clean the contacts?
  4. myronx19

    myronx19 True Classic

    Toronto, ON Canada
    I would start with the ignition system - check the connections, the cap/rotor/plug wires and the wire going into the coil. Even the reluctor pickup coil connection.

    Easy stuff first :) - do you have a copy of the Fuel Injection Diagnostics manual? I think it's in the wiki, if not - it should be! I've scanned it, so I can share it.
  5. Huey

    Huey True Classic

    Xenia, Ohio
    I battled with the exact same problem, spending countless hours chasing phantom vacuum leaks. If I advanced the timing, it would idle fine but it would hesitate on acceleration. If I retarded the timing, I would get the opposite effect. I finally gave up and took it to Midwest 124 to have Jon dial it in for me.

    Ultimately, the problem turned out to be a combination of TPS and airflow meter. He replaced the TPS (even though it was new, I guess it was defective) and adjusted the airflow meter spring -- he said they wear at a certain spot and adjusting the spring tension will fix it. It runs great now so I would check those two things.

    However, having said all that, if the problem seems to present only in damp conditions, it could be as simple as a cracked distributor cap.
    myronx19 likes this.

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