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Thread: 3300 '93 Stumbling off the line.

  1. #1
    Member PETC's Avatar
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    Default 3300 '93 Stumbling off the line.

    My '93 recently started stumbling off the line and sometimes will try and die while sitting at a light. Seems to happen more often on hotter days when the car has been sitting. Drives just fine to work in the morning and then has problems usually at lunch and on the way home. No vacuum leaks as I just hooked it up to a gauge and didn't see any surging. Plugs and wires were done recently. Fuel pressure is unknown. I can also feel it very slightly stumbling at constant speed while cruising on the highway but it could just be my mind playing tricks on me. MAF sensor was replaced when I got the car as it was bad and then replaced again with a nicer sensor but I'm still willing to accept that it may be down to the MAF sensor being bad as I've heard finding a good one these days is next to impossible.

    Possible Problem Causes I'm leaning towards:

    MAF sensor fubared.
    Fuel pressure problems.
    Coil-Pack problems.

    It only seems to happen under load and simply revving the engine while stopped elicits no stumbling.

    On an unrelated note I noticed that my AC compressor will cycle on/off while the motor is running even when no AC setting is selected... Is there a way to make it stop doing that?

    Thanks everyone!
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  2. #2
    Senior Member CorvairGeek's Avatar
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    First, the A/C problem sounds completely unrelated, but it isn't right. I would guess the control head (ventilation selector) may have some copper transfer in non-A/C positions, or a stuck compressor relay.

    Pull the vacuum line on the fuel pressure regulator and see if it has fuel in it. Sounds a lot like ours when the diaphragm was leaking.
    Jerry

  3. 06-19-2020, 01:23 AM


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    No fuel in the FPR vacuum line. Drove fine all the way home today with just a few hiccups.

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    Senior Member CorvairGeek's Avatar
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    Wish I had another suggestion, thought sure it might be a leaky FPR. These type problems could be so many things when initially so intermittent. I hate throwing parts at problems.
    Jerry

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    I do too. I suppose I could check the coil packs and see if one is going out.
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    Senior Member CorvairGeek's Avatar
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    How many miles on the car and fuel injectors? Have you ever or can you measure the resistance of all 6 injectors?
    Jerry

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    I haven't measured injector resistance but I do have a meter. Car had 112K on it when I bought it and has 131K on it now.
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    Senior Member CorvairGeek's Avatar
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    It crossed my mind later, at this age, the injectors could start being a problem if they are still first gen Multitec in '93. The resistance drops as the windings / coils short with age. A good set is 12.8-12.9 ohms (with my Fluke 77) for our '92 3300. The dying set was all over the place, with one at 6 ohms, but were were at 190K miles, though the previous owner had been fighting with them for some time (at least the dealer was taking his money for it). They get worse with heat too. Seemed fine cold, but failed as it leaned out.
    Jerry

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    I took the work van home tonight but I'll check the injectors tomorrow when I get the car back from work.

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    Sorry. Didn't get the a chance to check the injectors yet. Got tied up in father's day brisket making. I'll get those as soon as I have the time.

    https://imgur.com/a/jFs7BhM
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    Pontiac6ksteawd's Avatar
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    I also echo the Fuel Injector Sentiment.
    Brian - Carpe Diem

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    Senior Member 85_Ciera_Rebuild's Avatar
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    Quote Originally Posted by PETC View Post
    Seems to happen more often on hotter days when the car has been sitting
    Keep fuel tank filled up with TOP TIER Gasoline Brands., and change fuel filter.

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    Quote Originally Posted by 85_Ciera_Rebuild View Post
    Keep fuel tank filled up with TOP TIER Gasoline Brands., and change fuel filter.
    I fill up at half tank indicated 90% of the time and also fill up at Chevron or Shell 90% of the time.
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  15. #14
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    Quote Originally Posted by PETC View Post
    I fill up at half tank indicated....
    Change out fuel filter

    >It only seems to happen under load

    Load means more fuel is required.....a spark issue seems to be ruled out with this comment, " simply revving the engine while stopped elicits no stumbling," which requires less fuel, than when under a load. However, when revving, less fuel is required, and less spark energy is required...under load, full spark energy is required.

    If you don't know the fuel filter's history, then change out.

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    All good ideas and I will carry them out soon. Just been very busy and riding my motorcycle a lot recently. Sometime after the 4th I will tear into this and get back to you guys on everything I find.

    Thanks!
    ________________________________________
    My god... It's full of cars!

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