Skwerl

My S2 has recently acquired the habit of stalling after starting, and/or hesitating on acceleration. These symptoms are mainly present within the first 2 or 3 minutes of running (the stalling generally occurs within 10 seconds of starting), and it's only become an issue since temperatures plummeted. I replaced the fuel filter, oil, and oil filter in the past 3 weeks. I did some Techron about 5k miles ago. In addition to stalling, the car takes several cranks to start. I usually have to turn the key once for a few seconds, then one more time and it starts up in about a second. Is this a fuel pump problem, injectors, or what?

Longtime76

My 944S tends to hesitate and buck quite a bit when I first start it in the cold. Once it warms up there are no problems though.

However, a couple years ago the car would do that kind of stuff all the time, and would tend to stall a lot. The mechanic at the dealer eventually attributed the problem to a bad computer chip which was replaced and the problem was solved. This problem was persistent as opposed to just in the beginning like your car though.

Tom R.

When your cars are cold, no matter what the outside temp, does yours idle at about 800? It almost seems like I don't have a choke.

Lemon Yellow 87 n/a

hesitation while accelerating and bad idle CAN be caused by a bad dist. cap/rotor. Best to wait till Skipper answers this one though.

Skwerl

The distributor cap and rotor were replaced about 7 months ago. It usually idles at around 1000-1100, but the other day when I started it idled at around 600 or 700, feeling like it was about to die, until it warmed up about 5 seconds later. After that it was back to normal.

Also, I'm not sure if this is related, but I've noticed that since the cold weather started the performance doesn't seem the same. The only description I can think of is that the engine seems more "airy" or "reedy" now, as opposed to being "meaty." It feels like there's just not as much meat behind it anymore. Is that any kind of clue?

Longtime76

The performance hit in the cold is interesting, as cars perform better in cold weather than warm due to the fact that colder air is more dense and therefore contains more oxygen. I know once mine warms up, even though it is rough the first couple minutes while the engine is below temp, there is a definite difference when running in cold weather. I don't remeber the stats off hand, (I am sure someone here does) but I have always been told there is a given small percent increase in hp for every 10 degrees the thermometer drops (1%??).

emilysgranny

Swerl; there are a few things that can cause this.First thing I would check would be the fuel pressure reg or a bad injector.The tip off on a bad injector is to check the plugs or to just turn the key on but not to the cranking position and wait for 10 seconds or so. If you fire right away then ,check into the injectors.If your performance is weak when the eng is warmed up , then check your reg. Second would be to look at the idle control motor.The give away here would be the rpm when it starts ( should be around 1100 ) and the rpm in about 2-3 minutes ( 850-900 )in this cold weather.

Manning

Mine tends to have a fluctuating idle when it is really, really cold outside, like below freezing. It goes vroom, vroom, vroom up and down from about 1000rpm down to about 500 and back up. Not when I first start the car and not after it has warmed up, but after I have driven it a minute or so and come to a stop sign or light. As stated, it returns to normal idle (around 800 rev or so) after the car has warmed up a bit. It also still has normal throttle response from a stop, even with the funky idle.

I have all new gaskets on the intake and all new hoses and vacuum lines. I also have new fuel pressure damper and regulator. My guess is idle stablizer and if I hadn't had my head up my behind I would have gone ahead and replaced it while I had the intake manifold off this past summer.

Longtime, performance is better when it is cool out, not when it is cold, or at least very cold. The air may become more dense the colder it gets, but the fuel also doesn't atomize as well. This is why your car may tend to run more rich the colder it gets and cause you to get worse gas mileage.

Longtime76

Good point Manning, I had forgotten about the effects from atomization. I would have been better off to have said cool as opposed to cold. After all, cold for most Texans is not cold at all compared to most of the country.

Lemon Yellow 87 n/a

My car feels like it has 10 more lb/ft of torque all over the rev range in the cold. Of course, I could be imagining it, but it definately feels faster and has a quicker throttle responce.

emilysgranny

Manning ;when the engine is warmed up and you come to a stop and the engine rpm starts to do this , this is a sign that the tps is going bad . The brain is hunting for where the gas peddle is .Occasionaly a dirty mass air can also do this. HTH

emilysgranny

Lemon ; indeed you are correct about having more power in cold or damp weather. The air is denser in both cases.It is most noted on higher mileage cars and turbos.After all ,Porsche put its intercooler up front for this very reason.

Lemon Yellow 87 n/a

My car only has 99,000 well maintained miles on it though, I would not consider it a high mileage car (read about the turbo in a previous issue of 911 and Porsche world with 250,000 miles on it!!!). But you are right about damp weather where the air actually feels denser to your skin, only problem is that it aint as much fun as in cold dry weather cause of loss of traction.

Manning

Granny, re-read my post. I stated that my idle returns to normal when the engine warms up. I forgot to mention that my TPS is new along with the other bits and pieces

Also, as I sort of stated in that same post, a motor will not run as efficiently the colder it gets outside. The air charge may be more dense, but the fuel does not atomize as well, therefore it does not burn as efficiently. Note your winter fuel mileage versus your summer fuel mileage if you live in an area that has very cold winters. I can tell you just by watching my Air/Fuel meter that my car is running more rich, or at least less efficiently (even after it has warmed up completely). It may start to run better as the engine compartment gets warmer, but it will not run as well as it will in the fall or spring.

Type_LT

http://www.howstuffworks.com/turbo1.htm