Rough cold weather starts

[zuke448]

The last couple of mornigs my girlfriend has drove the car and tells me later that it was "vibrating" well I took the car this morning and it was running very rough until it started to register a temp on the guage. I am not sure what is causing this but I just changed the oil this past weekend but it was the same synthetic blend 10w-30 I am at a loss right now. Other than the rough starts it runs very good even when it warms up. Thanks again

[Blue Bowtie]

Warmup without load until the coolant temperature is at least 100ºF is always prudent, despite what the self-proclaimed geniuses at the U.S.E.P.A. might say they know about fuel mileage and pollution.

Engines waste a lot more fuel, emit a lot more pollutants, and wear a lot faster when run under load at cold temperatures. That wear will cause a lifetime of pollution and waste, compared to a minute or 90 seconds of running unloaded while warming up every morning until the coolant (and head) temperatures are sufficient.

If the ignition system in intact, what you are experiencing may be due to the necessarily rich mixture needed to get the engine started and keep it running until it is sufficiently warm to keep the fuel vaporized as it is injected. It the car is driven in this manner, even under light loads, the rich mixture can cause poor combustion, misfire, and contamination of the spark plugs, chambers, and engine oil. This will shorten engine life and cause you to waste more fuel and pollute more over the life of the vehicle.

[zuke448]

Sorry for taking so long to get back on here. (finals) i had let the car sit for a couple minutes because I know that cold weather is harder on the motors. But is there some sort of sensor or possible with the computer that is causing this to happen? It is possible that I also had gotten some bad gas. Took a trip and stopped at the only station in town (mom and pop) I am just trying to keep my car running its best. Thanks again for your imput.

[jeffcoslacker]

Other common causes include a leaky injector causing a fuel-wet cylinder after sitting that has to clear out, or a sticky IAC valve causing an incorrect cold start mixture, vacuum leaks that cause the mix to be too lean for cold run, and a throttle plate that's not fully closing due to deposits, which undermines the IAC's ability to control the mix, coolant temp sensor gone bad, making the ECM command wrong mix for the ambient temps, etc...

I suspect an injector leaks on my '97 from time to time...occaisionally, and only in cold weather, it smells slightly of gas in the morning and one cylinder misses for a few seconds after start up...oddly it has never coded for misfire though...

Could be you just got some watery gas making some ice crystals overnight in the line if it's that cold there...has to be pretty damn cold for that though...

[ChrisinVT]

Be lucky that's the only problem. When it gets below 30* (Seriously, 29* and this happens) my car will just NOT start. It'll turn over and over and over and over. It won't even attempt to fire up.

After carnking the car over until the battery dies, I have to connect a charger up to it. After 10-15 minutes of the charger I can attempt to start it again (an alternative to the charger is boosting it off my truck with my 0ga boost cables). Now if I start it and hold the pedal to the floor, about once every 5 revolutions ONE cyl will fire; just once. After cranking it for about 15 minutes doing this I can release the gas and the car will backfire (both through the exhaust and then through the intake). Once it does this I can slightly press the pedal and crank it. Then it'll catch on two cyls every 5 revolutions or so, then three, and when it gets to firing on the 4th cyl it'll kinda start to sputter. It'll eventually sputter along just enough to where I can stop cranking it and it'll idle very rough. I'll feather the throttle for a few seconds and it'll gain RPM and then the other two cyls will start to fire and the car will rev up relly high. It will misfire and run like shit for the first minute or so. After holding it about 3k for a minute, it'll continue to run on all 6 cyls and the car will act like nothing has happened.

This happens EVERY winter, and it only does it when it's 29* or colder. As soon as it hits 30* it won't have this problem. It also only does wit when the car sits overnight. When I have this problem in the morning, I'll get it running and drive to work. It'll be -20* out all day, but when I go to start my car after work (8-10 hours later) it'll start right up no problem. Then I'll go home and park it, wake up about 6-8 hours later and it won't start.

Last winter I had a house with a shop and kept the car in the shop - and no problems (never got below 45* in the shop). Now that I don't have a shop anymore, it's a fight every morning to get the car started. It usually takes 45 minutes to an hour and a half to get it started. This car only has 80k on it also. I have another car, a 1991 Euro with 240k on it, and she starts right up when it's -20* out.

I wish my car just ran rough when it was cold. That would be a blessing compared to having to screw around with it at 7am in horribly cold weather.