Ever since I bought my current Camaro a little over a year ago, it would idle and run really rough when it was cold outside and the engine was cold. I initially suspected the ignition system (being inexperienced under the hood as I still am), but figured that ambient temperature would not affect this. So now I'm down to two possibilities, at least; it's either the carburetor or the EGR.

The problem is, I'm not very familiar with either system. From the things I have learned, I'm guessing the problem is choke-related on the carb or the valve that allows exhaust gases into the intake is always open.

I only really know these things by reading and talking to a few people, but don't know how to start troubleshooting this problem. Anyone want to help out a nub under the hood?

 

sounds like the choke.youve had it a year. have you changed plugs, rotor, distributor cap and wires?? that should help anyway you look at it if you havent

 

I'm about to do all of that. I have a set of plugs in the trunk and about to get the MSD HEI upgrade kit (coil, cap, rotor, module) with some MSD wires (probably 8.5s for future upgrades).

I checked my current plugs just this past Friday, and they looked ok. I also checked the resistance on the wires and they seem ok, too. Still, I don't think this would fix my problem.

 

does it run ruff only when its cold out and when you start it up? and after it gets warm it runs fine? if so then welcome to the world of carbs, if thats whats happening let the car warm up 5-10mins in the morning before you go anywhere. basiclly the car is running rich when its cold and after it warms up it get to operating temps then it should be fine.

 

It's only when the engine is cold, but it should not run this rough. I do let it sit 5-10 minutes, but I doubt the car should act like this normally. I need some suggestions to get this back to normal.

 

ok does it shake alot cause then if it does that it's called diesling and thats realy bad notin you can do about it but let it warm up then it's all good cause everything gets cold a shrinks very lil cause of heat and conspation and contraction but yeah thats it it's happens to my frien in his 72 monty calro but his timing is retarted so but it still does it

 

Sounds like it could be the choke. If the choke isn't working, you would be running lean due to fuel condensing inside of the cold intake. A vacuum leak would cause a similar problem (leaning out the mixture by letting in extra air and reducing fuel) and it would also be more noticable in the cold due to the condensation of fuel. Something else that may be worth checking is the THERMAC if you have the factory air cleaner. You wouldn't think that it'd make much of a difference, but I had a horrible off idle stumble when it was really cold out. When I started looking, the flexible tubing that runs from the exhaust manifold heat stove wasn't connected to the THERMAC. After connecting it, the stumble is gone.

 

Haha... if it's just a disconnected piece of hose, I'd laugh at myself for days for missing it. Where exactly is the thermac (and what is it)?

Also, I'm not really sure if it's running too lean or not when it starts up in the cold. I am getting black smoke and a hefty stumble (almost sounds like a few plugs aren't firing) until the engine warms up.

 

well then its running pig rich and my car does that until its warmed up on a very cold day.

the thermac should be in the stock single snorkle air cleaner if you have the stock air cleaner on there, basiclly ull be lookin under the snorkle part and from there, there should be a like flexable metal tube that goes from the round hole in the bottem to the heatsheild on the manifold on the driver side

 

My car had this problem, the car would shake when cold in winter time and I just accepted it as how it was supposed to be.

What caused me grief on my car, was the emissions system. On my car, a valve that sits on top of the intake manafold was the problem, I think it's called the TV purge valve. It has two ports on it and one of these ports connects to the charcoal cannister.

I basically removed the purge valve, bunging up open ports and the car was happy to sit and idle in cold temperatures.

These valves are known to fail from time to time. What's supposed to happen is that when the coolant in the manafold gets warm the valve opens up and lets fumes from charcoal cannister into the carb. When the valve fails, it is in a permanently open state, causing your car to run rough when it's cold.

To test if yours is faulty, disconnect hoses from it and if you can blow air through it, it's stuffed.

 

Hey thanks for the heads up. It kinda sounds like the EGR valve but on a different location (maybe? I'm not too familiar, as I said). I'll look for it and try blowing air through it. Is it fine if this port is always closed? I'd like to get rid of all that emissions crap anyway; maybe a new intake manifold is in order...

 

Not quite like an EGR (although I think I see what you're mearning). The purge valve allows fumes from the gas tank to be fed into the carb when the engine is warm. This is the only way the tanks in our cars are able to breathe so if you remove all the emissions stuff, get either a breathable gas tank cap and block the breather line, or, run a hose from the breather line to under the car with a small filter on the end of it.

The port should only be closed when the engine is cold. If air passes through it when it's cold, your purge valve is stuffed.

You don't need to get a new manafold to take off the emissions stuff. I still have mine still on the car, and I want to keep my EGR valve, personally.