I have a 98 Silverado with 5.0 liter, 2 wheel drive. When cold it idles at 30 mph plus. When warmed up it runs just fine. This can be very challenging in icy weather. I have changed the temp sensor, cleaned mass air sensor, etc. Any help out there?
There are two temp sensors.
One for the computer and one for the gauge/light.
Did you change the sensor for the computer?
The one by the thermostat. Did not know there was two. Where is the computer one?
If the thermostat hasn’t been changed, now is a good time. I had a fast idle problem on my Corolla one time and it turned out to be a faulty thermostat. In my case it was fast idling when warm though. Not when cold. But to get to the bottom of something like this – fast idle problem tend to be difficult to diagnose – it is important that you start as a baseline with an engine having a properly working thermostat.
The sensor for the computer is near the thermostat, the sender for the gauge is in the left cylinder head between the first two spark plugs.
After two minutes of driving your engine should reach 100 F and idle @ less than 1000 RPMs.
If it is taking too long to warm up your thermostat may not be closing.