Car starts easier in cold?

1980Esprit

1980Esprit

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I have a 1980 Trans am with Turbo 301, and I am confused around something my car is doing. Yesterday I had started up the car to get fluids running, I also have the rear end up on jack-stands so that I can put it into gear and get both tranny and rear end fluids moving. However, the weird thing is that it was probably-10C out, and when I had started the car it had went into high idle for maybe 2-4 seconds until I kicked it off. The car was idling almost perfect. I had not started the car for probably a few weeks. (It was turning over for a while, expected for a cold start/old start, but it had started idling near perfect). During the summer time when we started it up, we would probably have to wait 5-8 minutes before taking choke off, and driving it out. (We have to wait for it to idle because we have to use S - turns to maneuver it out of the garage. In both, summer, and winter it is in a garage, and would say the temperature is almost the same for both times. We live in Central Canada so it does get quite cold out, and during the nights it might get down to -15C, -20C at this time.

We had not used a block heater, and the motor was stone cold both for summer and winter when we fired it up.

I am wondering if because the carburetor is out of tune that it is doing this, is there any difference in pressure between summer and winter?

Carb is running rich because where we got it the altitude was 1,048 m (3,438 ft) above sea level, and for where we are located it is around 445 m above.
(The car is running fairly rich, because when we start it up in garage we have to go out for warm up because if you do not go out. It will burn your eyes very badly from the gasoline--(?) and have to leave.)

Thanks for the help. I am just more curious than actually being a problem.
 
Automotive carburetors do not automatically compensate for altitude. Typically if an individual lives in a high altitude they lean out the jets and/or metering rods. I would first start with the choke though unless you know the carburetor has been modified. Recommend you get the factory Chasis Service manual and look in the carburetor section for adjusting the choke.
 
I am not very well known on knowing of adjusting carburetors, but I had taken one apart to see how everything works and where the parts go. I am 16, and the previous owners before had not done anything to motor/carburetor.

This queues me because I know that a carburetor has to atomize the gas, and does this better when it is warm (which is why a choke is involved to make it rich on starts I believe)

I had known that they had not adjusted to altitude which was I would have to ask for adjusting the fuel/air ratio on the bottom front of the carburetor, and then change the idle adjustment screw.

We bought the car last March, no adjustments. Would it be advised to start with adjusting the carburetor?

Another question about why it is starting easier, Would the molecular structure of oxygen in winter differ from summer? I am assuming you could get more air into the engine because of the oxygen would be able to have more atoms in the same space compared to when it was warm out.

I really appreciate the help very much! Thank you!
 
Yes start with adjusting the carburetor, especially the choke based on your description. Cold air is denser and has more oxygen. The screws in the front for mixture adjustment only effect idle and off idle performance. Once the engine gets into higher engine speeds they no longer come into play. Pay attention in any physics or chemistry classes you take, you will realize they have key information in understanding how the internal combustion engine works and cars in general.
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My thought would be that the car is running to lean, not getting enough gas in comparison with the air flow. When its cold the choke closes tight and you get less air flow meaning you get more gas.
 
chitownmikemc, you are correct in how the choke works but the OP stated it started up better when the weather was colder when the additional dense air adds oxygen and leans out the mixture. In warmer temperatures it ran rough when there was less oxygen so it was running too rich. Without first adjusting the mixture screws when fully warmed up it is hard to say if the issue is the mixture screws or the choke adjustment.
 
I'd first check the choke operation, to be sure the choke flap is fully opening when the car is warm, after about 10-15 minutes of warming up on these cold days. Then I'd check the mixture screws. Use a vacuum gauge, adjust each one until you get the highest vacuum reading at warm idle. You may need to lower the idle as you do this. Also, when the engine is warm, you should not see any fuel dripping out of the primary nozzles, looking into the carb when it is normal hot idle, or when the car is shut off. If you do, the float may be too high or the needle/seat is not working correctly.

Your altitude change really isn't that drastic, usually the carbs are jetted similar unless the altitude is about 5,000 ft or higher.

Burning eyes is evidence the car is running too rich. There will be some on these cars, especially if the catalytic converter is no longer there.
 
Hey guys, thanks for all the input. I will see maybe on Wednesday about adjusting them. Am I correct if the 2 screws on the front of the carb on the bottom are fuel/air, and the one located on the side is for idle speed? What is the RPM to have in park at idle when warmed up, or is it gauged when it is in gear?

After that is all over with, I will tell you if there is anything wrong yet, or experience any other outstanding problems.

I need a little bit of help for when I adjust the screws. Any tips?
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You are correct about the funtion of the screws. You dont have the factory Chasis Service manual for the car? There is a section on adjusting the carburetor. How about the emissions sticker on the area above the radiator which has the idle speed listed? The speed is adjusted while in gear with the parking brake on and the wheels chocked.
This video may help
http://www.youtube.com/watch?v=XRCUibTkm3o
 
I am not sure if you had known that my carburetor is awfully unusual. It is the q-jet used on the Turbo 301. I can not find the air/fuel screws anywhere. I had found the idle adjustment, just not mixtures. I have found somewhere on hte internet that in the later years that included mine, that the mixture screws were sealed off and mechanics caught doing anything with them had got a fine. Is this the problem I have? I know that I had seen 1 screw that looked like a male end of a philips screw driver in a hole where the mixture screw normally is. Except this end is inside of a hole about 1/8 of an inch inside. It had been on the right side when looking towards front of carb, the left side had something in front of it so I am not sure if that had been another one there or not.
 
I really appreciate all of the help you give, I am glad that you spare the time to help others out with troubles they face. I am now thinking that I will just leave the carburetor alone now. It was more of a pet peeve than problem and would not be a problem because next year we will be placing the 400 Poncho in. If it had been a simple adjustment of the screws there would have been no trouble for me to do so. For our new motor we have a fellow that my dad works with that will be rebuilding our Q-jet because he had a fair bit of experience. I have heard that Q-jets really like Poncho over any other brands such as Eddies, or Holley.
 
Mels, you are a wealth of information. I'm a new member, and not someone born in the 70s or 80s.

OP, I took my Holley 750 vacuum secondary 4 bbl carb off my Pontiac powered 400 '68 Le Mans, put on a 1977 Rochester 800 CFM, and I love it. The Holley worked great, but it was so rich with the square bore set-up, and it wasted gas compared to the Rochester. Now I only use 3 needle thicknesses of gas on the gas gauge to/from work with this car, instead of 4 lol.

That book by Cliff Ruggles is excellent, it's what I used when I rebuilt the Rochester. He's very helpful over the phone and internet, getting your carb set up, and with parts. Late 70s quadrajets are some of the best.
 
Holleys are good carbs but there are so many options and variations it makes it very difficult to get them dialed in properly. They take a lot of patience and expertise.

Rochesters and Carters are great for street cars as they are good performers, reliable and relatively simple to tune.
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