Ive got a 1981 dippy with a 225 super six. In the summer time the car runs great and I can tune the air/fuel mix down and lower the rpm's to a point where the engine doesnt diesel without any problems. However it's winter in western canada and while temperatures arnt super low maybe a -5 to 10 range ive had to fatten up the air/fuel mix and turn rpm's up quite a bit just to make the car driveable. The problem with this however is that I know its killing my fuel economy and unless I shut the engine off in drive it diesels for a good 5-10 seconds, sometimes pretty badly.

What can I do to make it run better? Is there anything I could be missing? as far as I know nothings amis in the engine bay. Maybe I should just tone everything down and drive with one foot on the brake and one on the gas until the weather warms up.

First I would determine why the engine diesels unless you mess with the mixture and idle. It should run fine with the idle speed and mixture at the correct factory settings.

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Casually looking for a Clifford hyperpak intake for cheap.

Well, I know that the engine is dieseling because ive set the idle and fuel/air mix so high. Ive had to do that because it runs so roughly and dies so easily while cold. Sometimes just shifting into gear or taking a corner at more than 20km/hr will kill the engine. However its better after raising idle rpms and fattening up the air/fuel. That is only a temporary fix however because now it creates the dieseling problem.

When I say the car is cold I mean its idled in the warm up phase for 5-10mins before I kick the carb down and allow it to engage the curb idle. So it isnt stone cold.

One other symptom that may be important is that upon hard acceleration the car will hesitate and choke for 2-3 seconds before engaging and taking off. Sometimes if im not careful it will die when I do this.

The behavior you describe sounds kind of like timing is way off. But why just in the winter? There are several devices that are either activated, or de-activated by the cold. It seems one of them may not be working properly. The EGR valve is supposed to open only on a hot engine and will kill a cold one. The carb picks up warm air when the weather is cold. There is something that changes the timing curve ( I think) when the engine is cold. The timing controls on that era engine were a bit of a mystery. They were playing with ways to cut emissions on cold engines with timing management that kind of messed with the drivabiity.

Could the carb actually be icing up? My friend's old VW will ice up on a cold day. It then behaves as you describe.

If all else fails, leave it in drive when you shut it off. And yes, Heal and toe driving is common with these old slants in the winter. I still drive all my cars with two feet because of my experience with my slant.

Sam

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Cold start the way it should run:

Step on accelerator ½ to ¾ to floor to set choke & high idle cam, release depress ¼ down, crank engine, it should start in a second or two and run at high idle at any temperture. After a few seconds you should be able to drop it into gear and drive off with no problem.


Is this a leanburn car? If so several sensors may not be working which will cause all kinds of drivability problems that become less of an inconvenience during warm weather. Having to play with idle A/F mixture seasonally is not necessary with properly adjusted and working carburetor. Check all system sensors, vacuum lines & their routing, grounds & connection to computer.


On top of possible LB sensor problems, I suspect you have a float level problem, choke adjustment and pull-off problem, perhaps cold air heater flap problem, accelerator pump problem, and vacuum leaks at manifold to carb and any pull-off diaphragm. Also, is the heat riser diverter at intake/ exhaust manifold free to move, and its passages clear? If this carburetor has not been rebuilt in the last few years it is time to get a kit and go through it.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

First of all thanks for the replies guys.
So im not sure if this is a lean burn vehicle or how much of a "computer" it may have. Im going to check vacuum lines and check out the carb while in operation to see if I can spot a problem. Otherwise the heat riser is working and is not obstructed so the carb is being heated that way.

Also @Sam Powell how can I test my EGR valve? Is it vacuum actuated, as in should i just check to see if its got vacuum pressure?

You know if the car is a "lean burn" vehicle because there will be a large plastic black box hanging off the side of the air cleaner.

I would start by thoroughly investigating your timing hardware. Check if the outer ring of the vibration damper has slipped and is no longer indicating true TDC. Check if your timing chain has stretched. Check if the mechanical advance mechanism in the distributor is sticking. Check your base timing.

Try temporarily disconnecting the EGR hose and plugging it. Try driving the car with the EGR valve unplugged. If it isn't any different, get a hand-held vacuum pump and apply vacuum to the EGR valve. Watch if the valve holds a vacuum. Finally, remove the EGR valve and check if the valve is closing all the way.

I would also make sure your choke mechanisms are connected, adjusted, and functioning properly.

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Casually looking for a Clifford hyperpak intake for cheap.