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Discussion Starter #1
I'm having two new issues in this cold weather. The truck isn't idling well during a cold start, idle drops down to 400 rpm and stall sometimes. I usually have to open the throttle to prevent it from stalling. After driving it and warming it up this isn't an issue. I read somewhere that a vacuum leak could cause this, but I thought a vacuum leak would make it idle higher not lower? The other issue I noticed is there is no brake booster power when its cold, the pedal is rock hard. Again, after it warms up the pedal is softer. Any suggestions?
 

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Discussion Starter #4
Clean your air bypass vavle
I did clean it a few weeks ago before this issue. It was also open 100% when it was stumbling / stalling. Or at least that's what my IAC psoition sensor claimed, I haven't ruled out the IAC
 

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Discussion Starter #5
Also more background info: I recently had the intake manifold replaced. Since getting the truck back I noticed this issue and also the brake pedal is rock hard when it's cold (as if there is not booster assistance). Could it be a possible vacuum leak?
 

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My '85 does the same thing, might not be as bad as yours, if I don't keep my foot into the throttle some it tries to stall (usually keep this up a minute or so). Then it's done and running well, always figured it was normal for a carb. How long does yours last for before it evens out?
 

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Discussion Starter #8
Mine takes about 5-10 minutes to warm up and then idling is normal, but it's totally dependent on weather. The colder it is the worse the idle is, even if the block heater is on. I have throttle body injection, no carburetor by the way. I ordered new IAC motor and I think I am going to adjust the throttle plates. When I'm idleing warmed up, the IAC position at a red light is 50% ish and I think that's too high. I will update the thread if I figure it out.

My '85 does the same thing, might not be as bad as yours, if I don't keep my foot into the throttle some it tries to stall (usually keep this up a minute or so). Then it's done and running well, always figured it was normal for a carb. How long does yours last for before it evens out?
 
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