Hot start issue
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Thread: Hot start issue

  1. #1
    FRESHMAN ROVER
    Join Date
    June 20th, 2018
    Posts
    14

    Hot start issue

    Been trying to solve a hot start issue for years and finally have a starting point. The issue is when the engine is hot and you start it after letting it set for 15 mins or so it has a rough idle for 10-15 secs then clears up or dies. I discovered today that when this happens if you remove the vacuum hose that runs from the IAC to the fuel regulator it clears up. Any thoughts?
    Thanks,
    Rusty

    FYI 1995 RRC 3.9

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  3. #2
    SENIOR ROVER
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    June 11th, 2016
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    northern va 22003
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    Re: Hot start issue

    by disconnecting said hose, you are introducing false air to the possible rich mixture. this allows for proper / better combustion mix. if you have diagnosis software you could look at sensor functions on real life, among other important components on any fuel injection system you need to look into coolant temp sensor for loose or failed connector, failed sensor, static fuel pressure and 02 sensor activity when hot.

    basically you may be experiencing a flooding hot engine.
    2k p38 4.6
    95 lwb 4.6
    01 d2 4.0

  4. #3
    SENIOR ROVER
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    Re: Hot start issue

    may I add, make sure you have a working thermostat. otherwise the readings by the temp sensor are null.
    2k p38 4.6
    95 lwb 4.6
    01 d2 4.0

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  6. #4
    FRESHMAN ROVER
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    June 29th, 2011
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    Re: Hot start issue

    I am dealing with same issue on my '95. It happens only after longer highway drive. I was thinking leaking injector or two making the spark plugs wet, but that should be happening all time. It passing "smog test" fine!

  7. #5
    FRESHMAN ROVER
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    Thanks for the info 95classiclwb . I’ve replaced the fuel temp, coolant temp and 02 sensors and fuel pump/filter. I’m going to try this weekend to test the wiring leading from the sensors to the ecu to see if that may be the problem. I’ll post results. Thanks!

  8. #6
    FRESHMAN ROVER
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    Well I’ve checked the fuel temp and coolant temp sensors and both are with parameters. It’s definitely a heat issue because in the winter I rarely have this happen. Could the MAF have anything to do with it? Thanks for all the help,
    Rusty

  9. #7
    FRESHMAN ROVER
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    If you ever figure it out please let me know. I’ve tried everything that I know to do with no success.
    Thanks,
    Rusty

  10. #8
    FRESHMAN ROVER
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    June 29th, 2011
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    166

    Re: Hot start issue

    Rusty. I agree with you! It never happens in winter.All my sensors check within the parameters, fuel pressure right on. Just passed Colorado emission test fine. I swapped ECU before... no difference. I may attempt to get it hot and when it happens again, take all spark plugs out, to see which one is wet and clean the fuel injector (s). But it usually happens somewhere on parking lot.
    Lets stay in touch, maybe we will figure this out.
    Eugene

  11. #9
    FRESHMAN ROVER
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    I’m glad I read your post. I was thinking about ordering an ECU and trying that route. If I come up with something I’ll let you know. Good Luck!

  12. #10
    FRESHMAN ROVER
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    June 29th, 2011
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    Re: Hot start issue

    One more thing my Rover does. In the winter or when it is pretty cold I have a "dead spot" in gas pedal and it sometimes stalls. I am thinking Throttle positioning sensor is causing it. Could it be that is gives wrong signal to ECU when is hot weather? I do not have a spare to test it. With multi meter testing, it has a smooth curve but it depends how tight are the screws holding it in place.

  13. #11
    FRESHMAN ROVER
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    Update. Just discovered that when I had my distributor replaced the mechanic bypassed the ignition module that was mounted at the coil (conversion for heat) and relocated it back on the distributor. Could this be a cause of the hot start issue? Thanks

  14. #12
    SOPHOMORE ROVER
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    Wimbledon UK
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    Re: Hot start issue

    I'd doubt it would give hot start issue.

    Thoughts about amplifier location relate to durability of components it's generally presented as. Amp just has to switch coil for HT, so if it does that then it's working correctly.

    Have you any hot condition compression test results for it? It may at least give you a combustion condition baseline to understand. Compromised pressure usually doesn't help hot start efficiency.

    What plugs are fitted? And what gap are they set too?

  15. #13
    FRESHMAN ROVER
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    No hot compression test. Used champion plugs and not sure on gap setting. What do you recommend on gap setting? At this point I’ll try anything. Thanks

  16. #14
    SOPHOMORE ROVER
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    Re: Hot start issue

    In my experience they need to be kept at their minimum spec setting, many advise to increase the gap which I don't feel helps.

  17. #15
    FRESHMAN ROVER
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    December 12th, 2015
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    Milton, Ga
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    Re: Hot start issue

    Quote Originally Posted by RRclassic95 View Post
    Update. Just discovered that when I had my distributor replaced the mechanic bypassed the ignition module that was mounted at the coil (conversion for heat) and relocated it back on the distributor. Could this be a cause of the hot start issue? Thanks
    Several of these items have already been discussed; however, I would recommend the following:


    • Remove and clean the ICV - spray cleaner into the plenum where the valve seats.

    Reinstall the ICV with pipe tread tape and a paper gasket.You may try adding an additional paper gasket if you are running an inexpensive GM ICV – I have found the plunger length to vary.


    • Reinstall the ignition amplifier to its original position. I have found them to heatsink and produce a degraded spark when overheated and old. The truck will stumble about, and struggle to maintain idle/ignition – will smell like it is running very rich too.


    I would address these items separately – I never like to change more than one variable at a time when sorting an issue.
    My money is on the ignition amplifier….

    Thanks,

    Chris

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