Sluggish Starting

Discussion in 'Fox 5.0 Mustang Tech' started by Strype, Jun 22, 2013.


  1. Strype

    Strype Cuthbert catcher Founding Member

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    My 93 has HCI, b303. It is very cold hearted. It has to warm up before it will idle on it's own. I've got it set to around 900 rpm. It stumbles down to 500 rpm, kicks up to 2000, slowly comes back down then stumbles again, maybe a slight pop out of the intake when it does this. Takes about 10 minutes depending on how hot it is outside.

    I got a new TPS last week, set it to 1.10, took the cone filter off, took the breather off of the valve cover, and it runs much better once warm. So is this a IAB problem (it's already been replaced once), or do I have a lifter not pumping up? I don't want to bend a valve on my GT40X heads.

    Thanks!
  2. mikestang63

    mikestang63 Mustang Master

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    Do the "Surging Idle Chcklist" Jrichker put together, It will answer your question.
  3. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    As suggested...


    You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix. :D:

    It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 125,000 hits, which indicates it does help fix idle problems quickly and inexpensively.
  4. Strype

    Strype Cuthbert catcher Founding Member

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    I'm going through the check list little by little. On a hunch I checked the timing that my neighbor set... It was at 20! Needless to say it doesn't pop out of the intake or start crappy now. I set it to about 14, and will probably drop it to 12 tomorrow. It didn't like anything less than 10 but I think that's factory. It is MUCH quieter now and doesn't rattle the interior anymore.

    Still searching for idle. I went ahead and replaced TPS last week and IAB this week. Gave her an oil change with some lucas added. :nice:

    Idle hangs about 1500 now and eventually drops. I'm gonna check voltage to the IAB tomorrow.

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