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Old 05-09-2003, 09:28 AM
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Post olds 455: engine idles rough when started cold.

i'm a little concerned with the idle of my stock olds 455 engine with 110K original miles. here is the problem:

if the air is cold (40-50) and the engine is cold, it will start up quickly and go into fast idle as usual. then, about 7 seconds later, a few of the cylinders will begin to miss. this gets progressively worse until the engine seems to lope badly.

during the loping, i notice grey smoke will come out the exhaust. it's not super-heavy, but i can see a haze through the rear window.

this behavior can last for around 30 seconds if i allow it. at this time, the cylinders gradually begin to fire again, untill all are running smoothly at fast idle. then, the smoking stops and everything is fine.

however, if i press and hold down the accelerator a little during the loping period, it usually causes the idle to return to normal within 5-10 secs.

the engine runs fine once warm. the loping only happenens when it's cold out, although it also did it this morning with the temperature at 65. it just rained, humidity was near 100%.

i should mention this behavior has happened since i bought the car at 85K miles. however, it seems to have gotten a little worse over time. used to only occur at 40.

to be honest, i like the way the it sounds when it lopes. it almost feels like i put a cam in it! but there's very little power, and it has stalled before while idling this way. i just have to wonder: when this is going on, is is bad for the engine? what causes this to happen? is there anything i can do to remedy the problem? could it be a vacuum leak?

the engine runs fine other than that. it uses a couple quarts of oil between changes, but this is partly from leakeage. it runs pretty smooth, and still has lots of power. i'm planning a rebuild within the next year.

thanks for your 2 cents.

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Old 05-09-2003, 12:48 PM
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sounds normal to me, everything needs to warm up
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Old 05-09-2003, 01:31 PM
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Idle Air Bleeds probably are clogged and not emulsifying well at cold tempetures.
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Old 05-09-2003, 02:57 PM
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OK, I'll step up to the plate! I've got a 455 with a "smog" Olds 350 Q-jet on it from a later year. I hate the darn carb but I can't afford another carb so I've made due with it and have learned some things along the way. I'll bet you a whole box of Crispy Creams and 10 dollars that your vacuum brake on the passenger side at the rear of the carb is kaput. What this little jewell does, is slightly pull the choke blade open at early start up so that the choke dosen't have the blade fully close while it's warming up, hense a very rich mixture and sooty fumes while cold. Once you get the new vacuum brake installed then you can "fine tune" it by slightly bending the brake rod until you have your desired idle quality during cold start. OK that will be 10 dollars and a box of Crispy Creams!!
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Old 05-09-2003, 03:35 PM
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[quote]Originally posted by dallam1:
<strong>OK, I'll step up to the plate! I've got a 455 with a "smog" Olds 350 Q-jet on it from a later year. I hate the darn carb but I can't afford another carb so I've made due with it and have learned some things along the way. I'll bet you a whole box of Crispy Creams and 10 dollars that your vacuum brake on the passenger side at the rear of the carb is kaput. What this little jewell does, is slightly pull the choke blade open at early start up so that the choke dosen't have the blade fully close while it's warming up, hense a very rich mixture and sooty fumes while cold. Once you get the new vacuum brake installed then you can "fine tune" it by slightly bending the brake rod until you have your desired idle quality during cold start. OK that will be 10 dollars and a box of Crispy Creams!!</strong><hr></blockquote>

I Agree with this Guy!
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Old 05-09-2003, 05:01 PM
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dallam1 seems to have the right idea. sounds like vacum to me
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