In hot weather tachometer jumps around

197,000 MILES • 4 CYL • 2WD • AUTOMATIC
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IOWASTEVE
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  • 1 POST
My car in hot weather at speeds over 55 mph and approximately 2,500 rpm's showing on the tachometer will drop and then raise back up about 200 rpm's on the tachometer. The car jerks a bit when doing this. I can't tell if the transmission is hunting in and out of high gear or slipping. It does this mainly when the cruise control is engaged but will do it when it's not. The cooler out it is the less frequent the issue. In cold temperatures it rarely does it. There are no error code indications with the lights for the gear selector on the dash screen. I have not checked it with a code reader.
Feb 5, 2019 at 5:04 AM
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STRAILER
  • ✓Experienced Mechanic
  • 55,512 POSTS
Hello,

It sounds like the engine is misfiring. but to be sure can you please shoot a quick video with your phone so we can see what is going on and hear the noise? that would be great. You can upload it here with your response.

This guide can help as well:

https://www.2carpros.com/articles/engine-misfires-or-runs-rough


Please run down this guide and report back.
Feb 6, 2019 at 6:21 AM
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