Throttle/Revs Up and Down...

spectra_freak · Apr 29, 2003

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?

Deaks2 · Apr 29, 2003

It's possilble your Idle Air Control Bypass Valve is on its way out. They will usually not trigger a CE, and if your car starts to stall then you know for sure.

LEDmod · Apr 30, 2003

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....

erok · Apr 30, 2003

Try a search on this subject. It has been discussed many times here.

MrSpiffy · Apr 30, 2003

Dirty throttle body. Same thing happened on our T-ho. Idle bounced between 400-650 then stopped at 500 where it should be.

~Jeron

TRD2000GTS · Apr 30, 2003

if u have a gt-s its supposed to idle at 700 RPM....so says a toyota tech i just talked to the other day....

-dustin

spectra_freak · Apr 30, 2003

erok said:
Try a search on this subject. It has been discussed many times here.

Can you please recommend the search words. I tried a search and didn't come up with much.

erok · May 1, 2003

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.

Chris25NJ · May 2, 2003

Anyone have a TB cleaning write-up?

RedNOSceli · May 2, 2003

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.

Vietnese · May 2, 2003

try resetting your ecu, worked for me

spectra_freak · May 2, 2003

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?

ArchangelX · May 2, 2003

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:

mike187 · May 3, 2003

mine was doing that after i blew a fuel injector

mike187 · May 3, 2003

Also, if you dont have C.E.L.I.C.A (Check Engine Light Is Currently Active) let your car idle in your driveway for an hour, thats how i got ine to turn on.

Throttle/Revs Up and Down...

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