Boosted1st

I will try and make this brief, but the symptoms are extensive. I am having massive drivability issues. There are some Mods on the car and it has always run better with each new mod, but now things have gone to mess and I need some knowledge. (this was a all-the-sudden-problem)
Car synopsis;
1994 GS 300
-Swapped 2JZ-GTE from 1994 aristo.
-Stock fuel system except an upgraded 255LPH Pump.
-Twins, Stock, "True Twin Mod"
-Greddy Front Mount-with Greddy Pipes. Stock BOV.
-Greddy Cold Air intake, K&N filter cone.
-AEM FPR
-MINES tuned ECU for the 440's
-Custom Exhaust, No Cats, Full 92mm back to the y, then 85mm back on twin pipes.
-AEM UEGO, AEM BOOST
-Greddy PROFEC A (commanded off for testing)
-Stock throttle body with stock sensors.
Now the symptoms;
-High Idle at start up cold 1500-2000 RMPS A/F reads normal 14.9 to 15.2
-Once operating temp is reached (185 degrees) Idle surges to 3000 RPMS in Neutral from a restart.
-If car has been driving Idle surges (in neutral) from 800-1550 in a cycle (heard it before on Hondas with bad IAC)
-Car is extremely loud and AFM readings bounce like it is in open loop (14.8 to 15.7)
-In Drive Car will hold 1050 RPMS and push on the tranny, Have to hold the brake down to keep it in place. Car wants too heat up (over 200 when I disconnect the fans), but the massive radiator I have wont let it.
-Driving, the car will boost well, but A/F Goes extremely Lean (16.5) briefly (2-4 seconds) then will drop into the 13 range.
I have attempted to disconnect all sensors to see if idle will stabilize. No luck. Throttle is sticky from closed position. No movement from butterfly when throttle sensors are disconnected, car still surges. I can get the idle to drop if I back out the throttle plate adjustment screws and push hard on the butterfly linkage at the throttle body.
PLEASE Give me an Idea where to start. This problem is driving me mad, and I cant drive my Supra in the rain...Thanks in advance for all your help.
Signed; A disgruntled 1st gen owner.

Boosted1st

Anyone can you help?

joewitafro

i had this same exact problem... I yanked off my throttle body and cleaned it profusely, added a heavier spring to help it return "more" because of this gummy issue... When I would push down on the TPS it would idle lower in the correct position, and the same things happened with a high idle restart (even if i could get it to idle great till warm... instant I restart it problem persisted). I then pulled off the idle speed control valve and cleaned that and no longer have this issue after cleaning those three things. Now I idle 1000-1100 pretty much always.

Try getting it to idle correctly, then yanking the plug to the ISCV and restarting the car to see what happens.

Boosted1st

Thanks for the advise, that was my very next place to go was pulling apart the throttle body...yay Saturday after work!!! Well I will keep you updated with the fix.

Boosted1st

This seems like a common enough failing on older swapped 2JZ's. I am going to start taking pictures as I work this issue, and see what I find out. Might even be worth a sticky when complete...but may not be...

Nixspeed

I would clean your tb like suggested but sounds like a bad tps. Do you have your trac hooked up at all? If so disconnect the trac tps and motor and see if that helps. They are both on the throttle body in front of the main butterfly. Also could be a bad o2 sensor. First thing I do with any of my many swaps is replace wear items. All seals, gaskets, sensors that are common to wear. To date I've not had any issues with a swap aside from some simple wiring fixes.

Boosted1st

Found the issue!!! The IAC was completely seized! I should have known this was the issue as I puked my aft turbo and have ingested quite a bit of oil, and it carbonized the valve into failure! DOH!!!!!! I feel really foolish... It is always the obvious things. The idle valve was all the way open, and when the car warmed up the TPS was set where it would clip the advanced signal and the car would die, then it would drop into open loop and the Idle would come back up....CRAP!!! Thanks for all the advice, it really helped...I was chasing wiring and thinking about having my ECU repaired, all for a stuck valve...Always check the simple stuff first. Now it is just a matter of getting everything set back to where it needs to be and Viola! Boost to the moon and destroy another turbo...lol

Nixspeed

It is always something you would never think at first and usually something simple. Did you just clean it or replace it completely?

Felixmanx

Nixspeed!!!! Check your Facebook please!!!!