307 Cold Starting Issues

[86Olds442]

Hi guys. It's been a few years since I've had one of these, and I've never had to deal with a hard cold start on a 307 before. Here's the deal: My 86 Olds 442 with original 307 severely hates cold starting. Choke seems to work ok. Once she starts, you feel the motor rock back and forth for 30 seconds until she smooths out and runs great. New (rebuilt) quadrajet, computer and all are hooked up. This is the first winter weather with this carb. Hope I'm just forgetting something dumb, Help? Thanks Guys.

 

[Peter]

my 231 is doing the same thing and maybe rocking back and forth for about 10 seconds. today it was about 15 degrees and it sounded like my timing chain was whining for a minute but thats because i run 20W-50 but i do at least need to run a thinner oil now (my car leaks some oil so i run thicker oil). It is kind of weird though because i ran 20W-50 all winter last year with no issues. i doubt the oil has anything to do with the starting issues that we both have. I have tried a bit of carbuerator cleaner to make sure the choke was moving properly and that ended up not being the problem.

 

[joe_padavano]

...Choke seems to work ok....

Uh, probably not. At a minimum the bimetallic spring has gotten weak and is not closing the choke plate far enough or not holding it closed with enough force once the car starts. Either adjust the coil or replace it. You'll need to remove the rivets and use self-tapping screws if the carb has never been rebuilt before and the factory pop rivets are still in place.

 

[Bonnewagon]

Chokes need to be properly adjusted and the choke "vacuum break" must be set right too. That's the little vacuum canister hanging on the side of the carb with an adjusting screw that opens the flap a bit upon starting. Some have it on the rear and it gets adjusted by bending the rod. Start by having a cold motor and the air cleaner off. See if the choke closes all the way when the throttle is tapped. If not adjust it so it does. Start it up and watch to see if the flap opens a bit. There is a spec for that opening in the manuals but you can experiment and get it correct. Generally, if it was fine in warm weather but dies out in cold, you need to close it up a bit (richen). Turn the adjusting screw a half-turn and retest. When it starts and stays running, you got it set correctly. Turn the car off quickly each time so the electric choke doesn't get hot and screw up the settings. In some cases you may even need to go out each morning when it's totally cold and readjust it until you get it right. Lots of work but a properly adjusted choke is a beautifull thing.

 

[joe_padavano]

Turn the adjusting screw a half-turn and retest. When it starts and stays running, you got it set correctly. Turn the car off quickly each time so the electric choke doesn't get hot and screw up the settings.

Half a turn? I suspect you are talking about the fast idle screw. I'm talking about the black plastic choke coil. Half a turn would be impossible. The fast idle screw is set to a specified RPM with the engine warmed up and the fast idle cam on a specific step. If your choke coil is weak or not adjusted properly, turning the fast idle screw is only a bandaid, not the proper fix. Get the choke coil set properly first. Also, the Olds 307 uses a hot air choke, not an electric choke.

 

[megaladon6]

before anything, just make sure the choke is closed, then check your timing. you may need a little more advance. since it's computer controlled, test the ECT to make sure the ECM is getting a proper temp signal

 

[billyjack]

The most common cause for those symptoms is inoperative or misadjusted vacuum breaks. As a general rule, the front break should open a closed choke about 1/8 inch. The rear break, which actuates after a short delay, should open the choke about 1/4 inch. After that, it's all up to the choke bimetallic spring and the electric heater. Applying vacuum to the breaks from an outside source is the easiest, but lacking a vacuum pump, you can always fire up the motor, observe the movement of the choke blade and adjust to suit. The 1/8" / 1/4" baseline might need some fine adjustment, but it will get you in the ballpark on any Rochester carb. Also, most factory settings on Q-Jets have the choke too far in the rich direction. I've drilled out the rivets, tapped threads for machine screws, and adjusted the choke to be barely closed at room temperature for a good baseline.
Bill

 

[Bonnewagon]

No, I was talking about the vacuum break. It is on the passenger side front of the carb with a vacuum hose going to the carb. Some are rear of the carb, and some have two, one is for hot weather. It has an adjustment screw on a metal arm that opens the choke butterfly a small amount once the car starts so it gets more air. Too much or too little and she dies. Doesn't matter what kind of choke it is, they all use one. Listen to Billyjack. 1/8 to 1/4 is right in the ballpark. I lean more to 1/8 in cold weather. If it quits and dies, make small adjustments until it starts and stays running on the first try.

 

[86Olds442]

Guys,
Thanks for the insight and advice. I'm sure that I can set this up right once this snow storm is over with. I'll let you all know how it goes and what it turns out to be. Thanks again.