[Sensor Fun] Ghost in my machine, idle oscilates

[puretone]

hey guys, my car's been in storage for a couple months
I checked all fluids, connectors and such (rats sometimes find their way in and nibble on wires...dont ask) everything kosher until a little bit ago it started oscillating wierdly at idle. It will quickly rev up to 1500 or 2000 RPM and drop right back down to 800-ish RPM, it just keeps doing that no matter what, warmed up or not.
Is that caused by dirty MAF or is the TPS screwy? I reset the ECU already, should probably look at error code...

[assassin10000]

Originally Posted by puretone

Is that caused by dirty MAF or is the TPS screwy? I reset the ECU already, should probably look at error code...

Dirty MAF, doubtful but possible.

TPS, possible - but storage shouldn't affect it, and would set a CEL most likely.

Usually with something like this (probably 95%), it's simply an air bubble in the cooling system at the IAC valve.

Andrew

[Celica RA45]

or fuel in tank gone off /stale if it has ethanol blended into it

[Roman]

Unplug the plug going to the idle speed controller, and see if anything changes.

[PHOENIX]

^ agreed.

Pull it and see if the surging stops, and the idle goes up to about 2000 constant.

[Roman]

I reckon it's a vaccum leak.

[puretone]

Originally Posted by Roman

I reckon it's a vaccum leak.

99.99% sure its not vac leak, i checked out all....that i know of.

i'll check the plugs.

doubt it's the air bubble, since it just randomly started....its got new fuel too...

[cps_goodbuy]

ecu based idle so maybe its just correction, but definitely shouldn't be having ants in it's pants

[mr220v]

Originally Posted by puretone

99.99% sure its not vac leak, i checked out all....that i know of.

i'll check the plugs.

doubt it's the air bubble, since it just randomly started....its got new fuel too...

Did you check for leaks in the gaskets between the head and the intake manifold? Loose bolts? I had this very problem once with my gen2 3sge, and it turned out to be a bad gasket.

[superfreestyle]

this is a very very very common problem with the blacktop 20v 4ag's... when they ship them over they get alot of corrosion on them and they usually seize up the ISCV (Idle Speed Control Vavle). this is also a common occurence for cars that have been stored for any period of time, it all depends on the climate.... unplug the ISCV and see if it stops surging, if it were me i wouldnt even test it... i'd just take the two screws off of it and free it up, you can usually just twist it back and forth and fix it.

[Roman]

That's true, one of my ISCVs was so jammed up, I had to soak it overnight in CRC to free it up, took a hell of a lot of cleaning it to make it spin freely again.

Was jammed rock solid.

[puretone]

hey guys, unplugged the TPS, that stopped the oscillations and raised revs to 2000-2500 RPMs. Unplugging the ISCV did nothing actually, having it and the TPS unplugged raised revs again asif it was only the TPS unplugged.
I am actually assuming this happened because I reattached the valve cover vent to the intake....betting the new surge of oil-based crap it usually got in the passed is now once again coming in the intake. I am taking my TB off I think and just cleaning the bejesus out of it. Is there some sort of TB gasket I should be careful about at all?? Assuming I probably need to special order one should it go pear-shaped on me....

Blast, I'll go measure that damned pulley for MANDALAY already now doooooohhhh!!

[Servin]

Oh chit I got to do that too!

[puretone]

no dice kids, i think i need to clean my MAF....will do tonite after much study of what/how the hell that is done.....i'm wondering now if my O2 sensor went apeshit....i'll have to pull code from ECU, which wires do I trip again?

[puretone]

okay here is:

took of the TB, cleaned all sensors, yes lotsa **** on all of them, didn't remove the ISCV completely because I figure getting rid of all the crap it was sitting is good enough, don't have the 5-point driver to remove it anyways...its not screwed down with a Torx screw, this is something else.
Still wild oscilation, now I come to discover that my TE1/2 pins are missing from the Diag plug, go me, i was wonder why the hell shorting TE & E1 didn't do anything and spat no codes....
Which one is it on the ECU side? Can't find it.....Blue & Pink wire? Warning lamp I can do with a 5v bulb right?
I am starting to think somehow it busted my O2 sensor because it seems to follow the Wave Form pattern suggested from Toyota...

[puretone]

Guys which pins on the ECU correspond to the TE1 & E1 pins on the diagnostic plug??????

[puretone]

I'm going insane.....

No faults on check engine light, it just blinks fast, no breaks in flashing....supposed to mean all is cool with ECU & Sensors....juuuuuuuuuust great!


if any of you have a suggestion, right about now is a great time that I would like to hear about it!

[puretone]

Originally Posted by superfreestyle

this is a very very very common problem with the blacktop 20v 4ag's... when they ship them over they get alot of corrosion on them and they usually seize up the ISCV (Idle Speed Control Vavle). this is also a common occurence for cars that have been stored for any period of time, it all depends on the climate.... unplug the ISCV and see if it stops surging, if it were me i wouldnt even test it... i'd just take the two screws off of it and free it up, you can usually just twist it back and forth and fix it.

those screws aint TORX, they are 5 points, wtf

i'm gonna have to look at that....

i soaked the ISCV in WD40 in an attempt for it to self-unstick

[puretone]

spits out no errors when it oscillates....idles high, 2000+ rpm. oscillates like crazy...

unplugging ISCV gives me code 33, which is correct.
unplugging TPS gives me code 41, which is correct.
unplugging MAF gives me code 32/31, which is correct.

Unplugging the ISCV stops the oscillation, but it returns every so often.
Unplugging the TPS stops the oscillation. "idles" formula1 style tho, 2500rpm.
Unplugging MAF, nothing works.

I DO NOT GET IT, WHY NO CODE WHEN EVERYTHING PLUGGED IN AND IT RUNS BAD?!

[assassin10000]

Is something causing the throttle body to stick partway open? That can cause this type of problem...

Andrew