rpm down and up - Toyota Nation Forum : Toyota Car and Truck Forums

aye87 · 11-26-2009, 02:19 PM

hi, after the celica has been warmed up, the rpm keep moving down and up, i just replaced spark plug, wires and checked it with timing light, its 10 btdc, what are the other problem most likely causing this rpm down and up, fuel injector is good, they making clicking noise and i poured gas cleaner

would it be?
timing belt
vacuum leak (rough idel only?)

timing belt havent change since it manufactured, it has 135000 miles

whatsyurprob · 11-30-2009, 11:51 AM

Quote:

Originally Posted by aye87

hi, after the celica has been warmed up, the rpm keep moving down and up, i just replaced spark plug, wires and checked it with timing light, its 10 btdc, what are the other problem most likely causing this rpm down and up, fuel injector is good, they making clicking noise and i poured gas cleaner

would it be?
timing belt
vacuum leak (rough idel only?)

timing belt havent change since it manufactured, it has 135000 miles

Timing belt is contributing to your prob. Change it. Vacuum leaks are also known for making the engine "loop". Inspect them all.

Rick89GTS · 12-12-2009, 02:23 AM

Check all your hoses, sounds like a vacuum leak. What year is your Celica?

RobMilkshakes · 12-12-2009, 08:18 AM

how much are the rpms fluctuating?

aye87 · 12-12-2009, 03:02 PM

1991 GT
-/+ 300 rpm flucating

seann · 12-12-2009, 03:39 PM

Fix your problem yet?

aye87 · 12-12-2009, 04:37 PM

no i visual checked the vacuum hose, but need further diagnostic

Rick89GTS · 12-12-2009, 08:44 PM

Check the AFM connections, TPS, ISC valve.

aye87 · 12-14-2009, 02:29 PM

its a vacuum leak
when i hold on the brake pedal rpm go down and maintain not flaunting but once release the rpm shoot back up more than it supposed to then rpm keep flaunting -/+ 300
i cant find the vacuum leak, all hose are connected and no rip i can see

aye87 · 12-15-2009, 06:58 PM

i think is the brake booster
rpm changes as the brake pedal is held

Rick89GTS · 12-15-2009, 08:58 PM

^Wow, the brake booster?!
That's a new one for me. I'm interested in how this turns out. Please post up your findings!

pritty123 · 12-16-2009, 06:54 AM

Need complete info and your problem as needed a detailed explanation.

aye87 · 12-16-2009, 11:38 AM

im gonna do the vacuum test on the brake booster but i think that where the problem, brake pedal is hard to depress and rpms changes as pedal being hold
if its not the booster, im goona use the propane method on the vacuum hose, then test each vacuum operate switches such as egr