Bouncing Idle

[Timon]

I've seen a few other posts about the idle being erratic, but nothing solved my problem.

When coasting in neutral, the idle bounces from 1k to 1.4k, up and down, constantly. However, it stops bouncing a few moments after I come to a complete stop, so it's really hard to figure out what is causing it. I'm guessing it does it while moving due to more air moving through the engine bay.

I've checked all the hoses on any around the throttle body that I can get to without tearing the whole thing apart, but everything seems air tight.

Any ideas?

[Bryce Scotti]

The same happened to my car. It was getting revs from 1k to 3k. The problem for me was a leak in my radiator. The hard thing is a radiator for a mr2 is expensive and hard to find. Well good luck

[Timon]

Radiator? I doubt that tbh, it isn't revving nearly as high as yours was, and my temperature is doing fine. It's always a possibility, but unlikely.

[deucegirl03]

so that is the ONLY time you notice the unstable idle?
hmmm that is interesting...
let me ponder that for a moment...

[Teado]

First thought was to look for a vacuum leak.

Second could be timing. I had this problem and the vacuum lines that connect near the front and under the TVIS is what I had loose. Pushed them all on and the problem went away. The stock clips are a PITA !

[328FTW]

They look like the water lines for the intake that warm up the intake for cold idle and warm idle. For some reason I had the same issue and I replaced those lines and it went away, air bubbles in the lines maybe? Dunno why it fixed it but it did.

[Luni]

Honestly sounds like a TPS or O2 sensor issue to me.

You should try unplugging your TPS and see if it acts all messed up all the time, or if it fixes your issue.

Im only guessing and my experience is limited to MK2s but toyotas are toyotas and most the time they share logic and operating reasoning.

[Timon]

Ya I couldn't easily check the lines under the intake, but I'll see if I can do that after my interview tomorrow.

AS for the TPS, it's something I never even thought of for some reason. I'm sure it could use adjusting anyway + it'd make it easier to check the vacuum lines under the intake manifold before I put it back in.

I'll take another gander at it tomorrow and see what comes up.

[Niko2511]

mine idles between 1.5 and 2.5 when i first start it up and slowly stops at about 2.25 when its warmed up. but when i turn on the ac it starts goin up and down again. cant get this thing smogged til i fix the idle. is it supposed to idle over 2k when its warmed up? i thought normal idle is about 800. other than that it runs fine.

[Niko2511]

o and i checked for codes and it came up with a code 1 (only blinked once) which means system is normal.

[Timon]

Actually on the MKI,

Cold Start: 2k - 2.5k depending on the temperature outside

As the engine warms you'll slowly see if drop, usually in about 200-300 rpm increments.

Warm idle: 800-1.2k (can be adjusted via the idle screw on the throttle body or via the air/fuel mixture screw on the AFM - hidden on US models)

It should not bounce at all once warmed up. Turning on something like the heater or A/C may make it move up/down, but once it moves with that accessory on it should stay there.

[Niko2511]

once i turn the the ac on it bounces. then it clicks and it stops for a few seconds then it will click and bounce again. it happens over and over it keeps cycling like that. having knowledge on ac systems and done work to them tells me it could be cycling on and off cuz of the pressure switch due to low refrigerant but the rpms will still bounce everytime it clicks back on. doesnt stop no matter how long i drive. y would the ac make it do that? with the ac off once its warmed up it will stay at about 2.25k for about 5 seconds or so then drop to about 600 (like at a stop light or something.) then slowly move back up to 2.25 then drop again. could be a vacuum problem thats all i can think of but wouldnt that throw a code??

[XJoshua]

If it helps I have the same issue. I just always blamed it on the AFM. Mine revs to 1K, then drops to 500RPMs and continues to bounce. Takes about 3 seconds to make this bounce. If I lightly push the gas pedal in 1/16th of a inch it does the bounce in about 1.5 seconds.

[Timon]

I actually resolved the issue just two days ago. There was a vacuum leak on the intake that was causing the car to run lean. When coasting the air escaping the engine bay differed a lot and the engine had to keep compensating for the change in air, hence why it bounced ONLY when coasting - not when at a completely stop.

[XJoshua]

Originally Posted by Timon

I actually resolved the issue just two days ago. There was a vacuum leak on the intake that was causing the car to run lean. When coasting the air escaping the engine bay differed a lot and the engine had to keep compensating for the change in air, hence why it bounced ONLY when coasting - not when at a completely stop.

If Im sitting for more than 20 seconds itll bounce. If coasting itll bounce. When in gear it drives fine.