Car engine revving problem, need advice.

Hello,



I have a 94 Galant with about 140,000 miles on it. This past month something really weird has happened to me three times that I'm hoping so Arsians out there can clue me thi bang lai a1 in on.

My car normal idles at ~600rpm, put it in neutral this is where it sits or if you're stopped at a light. Well three times now when I started it up the engine starts revving. It will rev up and down between 1,100 and 1,600rpm. It will shoot up to 1,600, drop down and as soon as it hits 1,100 it shoots back up to 1,600, over and over. It does this when it's in park or neutral. If I sit in drive at a light it refuses to drop below 1,100rpm.

It just randomly happens, I'll start up my car to go to eat dinner and it does it, when I'm done with dinner and go home it's fine. I've tried turning it off and then back on immediately when it happens and it still does it. I've tried revving the engine in park and that doesn't affect anything. The only thing that seems to work is time, if I let it sit for 30+ minutes, next time I start it there is a very good chance it won't happen. However, the times it has happened my car has been sitting anywhere from 30 minutes to 4 hours. Like I said it's random.

Anyone have this happen to them? Anyone know why it's happening?



Please help



I didn't find the right solution from the internet.



References:

https://arstechnica.com/civis/viewtopic.php?t=878518

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Thank you