My car doesnt chug in the summer or warmer weather, but when it gets cold it chugs at 70mph, what could cause this

first check No.5 spark plug wire closely...change if necessary....if good then change crankshaft position sensor.

You stated that it was hard to start. Did it crank over more slowly than usual? If so the motor oil may be too thick for below zero temperatures. If it cranked normally, there are a number of things that can cause this.This car has fuel injection controlled by the computer(ECM). If the temperature sensor for the ECM is out of specifications, then the ECM will not fuel the motor properly when cold starting. Old age, lots of miles can lower compression and cause hard starting. the fuel injectors may be worn, defective or clogged, delivering the fuel pooly. Was there a check engine light on? This is before mandated ECM monitoring, but if there is a light on, there is a way to check what it is causing it. There are other things like cracked vacuum hoses that can affect the starting. Worn spark plugs and wires can have an effect. When it chugged coughed and spit, was there black or blue smoke coming out of the tailpipe? Black smoke is too much fuel and blue smoke is oil consumption. I know that it is hard to decide where to go for repair, but the dealer has trained personnel, and a warranty for repairs. In my experiance as a dealership technician and an independant shop owner that some things are better off at the dealer, unless the independant shop has factory trained people and lots of information available, you may be charged with them trying to learn on your car. I had a 1987 LeSabre that when the temp was way low, the coil pack failed to spark the car.

dont just change parts without knowing--scan car at a parts place 1st-------it cud be a failin fuel pump or pressure regulator----or an egr valve--dirty injection system-----worn plug wires------fuel system pressure test or ignition inspection may be in order

Change the fuel cap. It may not be venting properly.

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High MPH and chugs = Clogging fuel filter. Also check the air filter. No beer needed.

I do not know much about this vehicle but if it is diesel it sounds like you should clean and or replace air filter and or glow plugs or grid heater... if it is a gas vehicle changing the fuel filter and checking spark plug gaps and plugs and wires also the cap and rotor may have where witch will cause intermittent and weak spark so you could be getting to much fuel and running rich. also if it has a catalytic converter you may want to check if it is partially clogged and if it is have it replaced hope this helps good luck

sounds like a fuel prob injectors or pump would be my guess have fuel pressure checked 1st though

Change the mass air flow sensor (maf) . Summer months tend o be humid, this could cuz the sensor to react strangly and alter the Stoch/richness or the air-fuel mixture....Check it out tell if it its helpsful, if not There are acouple others we can look at..

Sounds like the system lacks fuel pressure, check the fuel pump pressure.