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Old 07-14-2008, 10:33 AM
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Poor Idle on 1991 MS 351 Indmar

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My 1991 Tristar 351 Indmar has always run great. It starts fairly well but idles in "surges" or "chugs". I have cahnged the fuel filter and adjusted the idle speed up a bit but it still doesn't idle very well. It runs great at high RPM. Any ideas? I don't want to lose 2 weeks in the shop at this time of the year.
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Old 07-14-2008, 10:42 AM
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Mine was doing this just last week and it was running too fat, I leaned the mixture with the screws on the side of the bowls and then upped the idle a little. Per a friend I need to fatten the mixture up a bit because as lean as I have it I may burn up the cylinders but it wont be nearly as fat as the PO had them. One of them was almost all the way out. Here is a PDF on your carb, it has all the adjustment info.

http://www.tmcowners.com/teamtalk/sh...ad.php?t=24873

O and welcome, hang out here and do some searching, there is awesome information.
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Old 07-14-2008, 11:00 AM
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If idle speed was never a problem before, it won't fix the problem you're having. How long since the last tuneup? Has the flame arrestor been cleaned recently?
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Old 07-14-2008, 11:30 AM
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JimN:

Thank you for your comment. The problem started a couple of weeks ago. It was never a problem before. I have never had a tune up done. (it only has 400 hours on it). I changed the spark plugs about 10 years ago. The flame arrestor is clean.
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Old 07-14-2008, 01:21 PM
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You think a car would run well if it had a tuneup 10 years ago and hardly ever ran?
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Old 07-14-2008, 02:12 PM
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Poor Idle on 1991 MS 351 Indmar
Team:

My 1991 Tristar 351 Indmar has always run great. It starts fairly well but idles in "surges" or "chugs". I have cahnged the fuel filter and adjusted the idle speed up a bit but it still doesn't idle very well. It runs great at high RPM. Any ideas? I don't want to lose 2 weeks in the shop at this time of the year.


I would like to see some pics of this 1991 MariStar TriStar, if that's what your referring to. It has to be one or the other, but not both! TriStar model from 1987 to 1991 and MariStar from 1989 to today.
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Last edited by TMCNo1; 07-14-2008 at 02:19 PM.
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Old 07-14-2008, 06:48 PM
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You wont burn up cylinders with a lean idle. It just wont run as well.
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Old 07-15-2008, 10:00 AM
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It is a Tristar
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Old 07-15-2008, 10:29 AM
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I always did plugs every year. I think she just needs a tune-up per JimN's recommendation. They do a lot of sitting around and I would bet you have some fouled plugs by this point. The carb shouldn't just go out of adjustment like that. I woould just swing by autozone and grab some plugs - also check your cap, rotor and wires - make sure the rubber bushings haven't dried and cracked. My 2 Pennies...
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Old 07-16-2008, 05:28 PM
Storm861triple Storm861triple is offline
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Quote:
Originally Posted by learjet2230 View Post
You wont burn up cylinders with a lean idle. It just wont run as well.
I agree. You won't even "burn up cylinders" at WOT, running lean on an engine that makes 41 hp/liter.

OP; the symptoms that you're describing are indicative of an improper air/fuel ratio at idle. While you can adjust the idle mixture screws as described and probably solve the immediate issue, I agree w/JimN that the engine is overdue for a "Tune up", which would include adjusting the idle mix adn idle speed...among other things.
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