Hi,
I have a 2002 STS with 99k miles.
If the car has been sitting for more than 30 mins or so and I start the engine, it will idle a bit rough and misses like it's running on 7 or less cylinders. This goes on for about 5-8 seconds then it runs perfectly for the entire trip until next time it sits with the engine off. For example, when I go to a store, shut it off, do my business and come back to restart the engine, as long as it's been less than 30 mins it runs fine, if it's been sitting longer, it will do what I've described above.
When it acts up, I get a random engine missfire code, but after driving for a short while, the CEL goes away.
My initial thought is the head gasket (s) is starting to bleed some coolant into the cylinder(s) when the car is off and the cooling system is still pressurized.
Any other ideas?
I have a 2002 STS with 99k miles.
If the car has been sitting for more than 30 mins or so and I start the engine, it will idle a bit rough and misses like it's running on 7 or less cylinders. This goes on for about 5-8 seconds then it runs perfectly for the entire trip until next time it sits with the engine off. For example, when I go to a store, shut it off, do my business and come back to restart the engine, as long as it's been less than 30 mins it runs fine, if it's been sitting longer, it will do what I've described above.
When it acts up, I get a random engine missfire code, but after driving for a short while, the CEL goes away.
My initial thought is the head gasket (s) is starting to bleed some coolant into the cylinder(s) when the car is off and the cooling system is still pressurized.
Any other ideas?