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I just went out to car and started it (approx 25 degrees outside where car is now) and car started fine but again a rough idle after the cold start. I then unplugged the IAC and the idle sped up and smoothed out.....plugged it back in and it went back to rough.


Car idles very rough when cold . The above is all that was available for me to see, that's why I asked form the information I did. A/F mixture is non-adjustable on this car. We need to check for a lean condition when cold started. Add propane or starting fluid on the cold start to see if it smooths out. If it does, we're too lean.


The idle of a car engine is kind of like a human heartbeat: You can tell what shape it's in just by listening. Problems with idle speed—things like slow idle, fast idle, rough idle, or stalling after idling for a few seconds—are symptoms that something is wrong with your engine.


Rough Idle When Starting Cold, Then Goes Away When Engine Is At Operating Temperature More Details Below I have an older, low mileage vehicle with a V8 engine. When the engine is started cold, regardless of the outside temperature, the idle is rough and there is a noticable power loss.


Rough idle in cooler weather below 50 degrees. Runs fine while driving at speed, but rough idles or stalls when stopped. The rough idle clears up after 15-20 minutes or so when the air temp is above 45, but it lasts longer when temps are below 45.


So, your car, truck, or van is idling rough… what is the cause? And what can you do to fix it? Even if you aren’t the savviest person when it comes to vehicles, you should know how to identify rough idling. Rough idling is a common problem, of which the exact cause can be difficult to diagnose, as several factors may come into play.


Here is a car repair that brought me back to basics. A customer with a Mazda 626 and a four-cylinder engine had a very rough engine idle. However, the complaint from the driver was a lack of power. They didn’t seem concerned with the engine idling problem.


Running Problems. Rough Idle. If the car starts when cold but, idles rough or does not want to stay running, this can indicate a problem with the engine temperature sensor. When the engine is started cold, the engine temperature sensor sends a signal to the DME control unit to provide a richer mixture.


I have a low mileage 560SEL. On cold start the car idles rough and there's a huge loss of power. Once the coolant gauge reads 80 degrees C, the engine smoothes out and the power comes back. During rough idle the tach reads around 500 rpm and the needle shakes. Economy gauge moves towards the center. Any guesses?


In this video I show you how I diagnosed a poor running 2001 GMC Yukon when the engine is cold. This is a very common problem on all GM V8's. The lower intake manifold gasket will always leak ...