View Full Version : Celica, Bouncing idle 1200~1900 rpm. MASTER TROUBLESHOOTERS, step inside once again!

06-21-2005, 05:24 AM
So....I have a new map sensor, and i have a huge bouncing idle even at full warm up temps. It ranges from 1200 to 1900 rpm. 1991 Celica 5sfe manual trans.

The vehicle suffered previoiusly from a surging condiiton at partial throttle. Engine codes told me to refer and replace a Coolant temp sensor and a MAP sensor. Both are replaced. Ive read many troubleshooting stories and Ive done a few things to figure it out.

Looping the 2 egr hoses does nothing, even disconnected the engine doesn't change anything at idle. Almost like it didnt exist.

Unplugging the MAP sensor and plugging the line (sensor bolted to the strut bar on the firewall) yelds smooth idle, and the car is driveable without any bucking, But runs PIG RICH. Yeilds a 31 ENGINE CODE, due to vaccum hose being plugged, yet sensor plugged in.

Running the vehicle with the new MAP sensor plugged in, Pulling ECU codes, the light blinks rapidly indicating normal performance, then after 59 or so rapid blinks, a error 51 pops up. Haynes manual tells me TPS IDL circuit (throttle position sensor idle circuit?), ACCL pedal, ECU or A/C switch circuit. The 3 wire TPS responds accordingly testing continiuity between the middle , top, and bottom pins. I see an adjustment screw on top to adjust the angle, I'll play with that. A/C circuit works, its freezing cold, Anything else?

The vehicle has never run properly in my ownership. It HAS THESE NEW PARTS: TPS, o2 Sensor, Igntion coil, distributor cap, wires, plugs, rotor, Coolant temp sensor. ALL FROM OEM TOYOTA. MAP sensor was used from another vehicle. ECU has been swapped with a like vehicle to no avail. The vehicle used to suffer from a surging problem at about 70% throttle, it would buck and jerk.

06-21-2005, 05:41 AM
Ive twisted the TPS sensor along its adjustemnt range, standing on teh drivers side looking at the TB, if i take the top of the sensor and pull it toward me it still idles up and down, if i push the top of it away from me, it spikes to 2000 and stays there. In the range of adjustment there is very little difference in idle rpm.

06-21-2005, 06:15 AM
So... Maybe I missed it... And you said you already have a new rotor and dizzy cap... But have you tried replacing the seal on the Dizzy itself? Along with taking the thing apart and cleaning it or better yet a new one all together? Who knows, it sounds like you've checked a crap load of things, it could just be something that simple.


06-21-2005, 06:55 AM
I have that same question too.. My idle will sit high like 1200-1400rpm.. even after the engine has hit temp.. But if I do somethin like shut the engine off.. go into the store.. etc.. when I start it back up it'll idle normal... like around 800.. 850.. I pulled both coolant temp sensors and cleaned the threads and cleaned the sensors themselves.. with no change.. I checked the throttle body air by-pass screw as well.. It's just about fully closed.. Like a half turn from bein closed.. I prefer a higher idle around 950.. That would be fine but this 1200-1400rpm bullshit is annoying... :(

06-21-2005, 07:30 AM
Just tested the voltage going TO the Map sensor...5v..perfect, I guess i'll check the voltage at the ECU next.....

I want to mail this MAP sensor to someone to see if they can test it..

06-21-2005, 09:24 AM
I unplugged the EGR....and it didnt do crap...... hmmz.

06-21-2005, 11:56 AM
The sensor or tip of the hose isn't cracked, is it?
Problem sounds like a v leak, but with that hose plugged, no surge....hmmm

06-21-2005, 06:25 PM
Im going to play with the EGR next, I looped the EGR on to itself, and no change in idle or performance.....

Im going to try cleaning it out and seeing what the deal is.

06-21-2005, 06:52 PM
what are your TPS readings at idle, 1/4 throttle, 1/2 throttle, 3/4 and WOT?

06-21-2005, 09:44 PM
what are your TPS readings at idle, 1/4 throttle, 1/2 throttle, 3/4 and WOT?

I was just testing for continuity since i have the 3 wire version.

At idle the middle and bottom two pins read continuity. At 80% and up the middle/top reads continiuity. Inbetween thoes points, none of the pins read continiuity.

06-21-2005, 10:12 PM
wtf do you mean continuity? If they have voltage through them you can't take a measure of resistance.

06-21-2005, 11:08 PM
Ok so Problem fixed, I removed the throttle body today to take a look insdie the Intake Manifold and spray car cleaner inside. Incidently I had the car running and it was creating this huge sucking noise, Turns out the Idle Screw was backed ALL THE WAY OUT, i figued that out while i had the Throttle body off the manifold.

So the idle is fine, it pulls good power, BUT it idles at 1000,1100 RPM. Even with the Diagnostic Port wired into Testing mode, it still idles at 1000,1100 rpm. The screw is even screwed ALL the way in, TPS adjusted at its full range, and it still idles at 1000,1100. Ive tried to adjust the Idle control unit...to no avail.

Any proper way to adjust the idle via the computer?

04-12-2009, 02:29 AM
i had a high idle problem that was due to a vacuum leak. The vacuum lines to the ac thing were backwards, the vacuum lines to the power steering pump were cracked and the gasket between the egr and intake manifold was messed up