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Discussion Starter · #1 ·
Some nights when it gets cold out after a warm day (say 65 degrees down to 40 degrees) my car will rev up and down like 5 times and then settle into it's normal range of 750-ish or so RPM. It seems like it bounces between 700 and 1000 RPM back and fourth a few times. Does anyone else experience this? It doesn't happen often, but it seems to be when the temperature differential is large from day to night. Any ideas?
 

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I used to get that often at cold weather... at fresh start in the morning...
When I had like no back pressure cause of the straigh pipe(unbolted) setup.. it did worst...
But now that I got some back pressure back.. it rarely does it now...
But this is my case.. not sure.. how will it effect it though....
 

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Try "rpm bounce". That brought up a couple threads. It's nothing to worry about unless your car stalls or revs really high (over 2000). Many people have had this happen including me and nothing came of it. There's a correllation between the rpms bouncing and hard braking, ie. "I stopped at a light and noticed the idle bouncing up and down." Usually a tap on the throttle will settle the engine down. No one has ever conclusively explained why the bouncing idle happens as far as I know, and very few have ever had it be a real problem for them.
 

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once again, its secret toyota engineering...

Im willing to bet its some kinda of ECU glitch, where two varriable cause some kinda of 'loop' (programming, if -then) untill that one varriable changes and kinda 'kick' the program back onto the right track...its all computer related.
 

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Discussion Starter · #12 ·
Thanks for the info guys. I'll also try resetting the ECU. I also heard to get some fuel injector cleaner and put it in your tank and fill up with gas. It's supposed to also clean the throttle body, but I don't have much experience with this. Anyone had any luck with the products?
 

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Also guys...You're forgetting it might be an air leak somewhere before the throttlebody, before the air intake. :gap:

My 7 had a leak in it's throttle body, and it was causing the revs to modulate...up and down, up and down. That was the problem, though.

Take some carb-cleaner and spray around the area, if your car revs up, then you know you've got an air leak.

Be careful though... :chuckles:
 
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