OH hey man!! well... unfortunately, I just sent my ecu out this morning to get repaired by AutoECU. I can try to repair the spare ecu I picked up the other day. It wasn't leaking nearly as bad as my old one.

 

OK. I am really confused about the ISC valve now because I tested my Supra's ISC valve and it is doing the same thing, I don't remember if my Supra had an idle issue...

pics and vids:

Cleaned the housing.


Inside the ISC valve








Connected positive terminals


Valve terminal numbers


Supras ISC connected


Retracted in


Extended out


So I know the extent to which the ISC valve should move...

here are the vids of what happens when I supply power to the ISC valve as per instructions in Toyotas manuals

My Lexus ISC, notice how the valve doesn't budge with power supplied:


My Supra's ISC, notice how the valve jerks just the tiniest bit, but doesn't actually move at all:


Any thoughts? Do I have TWO bad ISC valves? or am I doing something wrong? or is this normal?

 

It could be a clogged cat. I've seen clogged cats prevent cars from running not necessarily a SC but on a CRX the cat was clogged had the same symptoms you had. Once that was replaced it ran perfect.

 

^thanks for the feedback. I'm still trying to source replacement cats as well.

I also am noticing that my cylinders are either flooded or close to flooded, as the spark plugs are wet with fuel when I pull them out.

 

So. Replaced all the ignition components (spark plugs, wires, coils, distributor rotor/caps) and 1st start up was fine, running super rich because my O2 sensors are still in open air and not installed into exhaust piping. CEL code 24 came on (IAT sensor). Second start up was fine, made a little video. IAT sensor is the MAF and since I have three of them.. I tried another one. Third start up with a different MAF returned to the whole "won't start unless I am pushing on the gas pedal". And after that, it did not matter which MAF of the three I used, car refuses to start unless I depress the has pedal. Code 24 only. I checked resistances on all three of my MAFs with the multimeter set to 20K ohms and all three MAFs returned readings of 1.87 between terminals 1 and 2 as per the TIS. With my multimeter set to 200k ohms, all three read at 1.9. I'm not sure if I did this correctly. The manual says resistance with air temp at 68 degrees F should be 2-3Kohms. Does this mean all three of my MAFs are bad? I'm also suspicious that the ECU is still a problem, won't know for sure until I get my rebuilt one back. I'm going to attempt to see if I can find a short in the harness... but given my electrical expertise, I have no idea what I'm doing lol

 

Finally got the cats off. Condition of car right now: Open manifold (primary O2 sensors attached, secondary in open air), all new ignition components OEM from Lexus, no CEL codes (symptom of bad ECU), new walbro fuel pump, K&N OEM fit air filter, used ECU with leaky capacitor still (mine is getting rebuilt with better hardware and should ship today), and everything else is in order and working condition. Problems: When starting WITHOUT foot on gas, start ups and dies immediately, when starting WITH foot on gas, will run for as long as my foot is on the gas.

Now, let's say that in two days when I receive my rebuilt ECU with lifetime warranty and install it, and I STILL have the same problem, does anyone have ideas what may be the cause?

 

Just installed my new freshly rebuilt ECU. Same issue. Car starts up immediately then dies immediately. If I give it gas, she'll run but only for as long as I give it gas. As soon as I let off the pedal she dies.

Details as of now:

New rebuilt ECU with no codes (only ran for a couple minutes so codes may not register yet)
New ignition components (plugs, wires, coils, rotors, caps)
New fuel pump (walbro, the one that was meant to go in the supra)
Sensors should all be good.

Car starts, but dies immediately unless I have my foot on the gas.
Car will rev to wherever I want like normal
I found out that if I let off the gas super super super slow, the car will idle at 300-400 rpm
If I let off any faster than that, the car just dies off

My opinion: I'm starting to feel like it's fuel related. Like the engine isn't getting the correct amount/pressure of fuel at low rpms/idle. I'm starting to think I need a new fuel pressure regulator and/or fuel pulsation damper.

Your opinions?

 

I have never heard of a regulator or dampener causing major issues like that, those parts are usually bulletproof.
the fact that you can start it with your foot on the gas tells me your iacv is most likely stuck at a warm idle position.
It's supposed to cycle and reset to a starting position when you key on, but since they are 90% of the time in the warm idle position, thats where they normally fail causing a no start because warm idle uses much less air than a cold start.
are those supossed to be videos of the iacv? none of the videos are working for me just look like pictures.

It could very well be your iacv, I have not had much luck with opening them all the way that far like you have and then them working after that.
Nowdays I never remove the black plastic part from the flange that has the plunger on it, I just use wd40 on the plunger shaft and turn it a bunch to make sure the plunger can turn freely.
so you are supplying power to the 2 pins, and then grounding one of the other terminals to get it to move right?
depending on which one you ground is the amount it moves.

you can always normally get the plunger to go in and out by hand, but when the magnets in the base get weak or demagnatized in spots, the iacv will not be able to rotate the plunger side anymore.

to test it out you can use the set screw on the throttle body to adjust the throttle blade open some more, which raises your base idle some. if it start and runs fine its prob the iacv, don't expect it to idle at the right rpm though and your idle will increase as the engine warms up with no iacv.
OR, you can take the iacv out, set it where its least sticking out (allows the most air to pass through the passage under it), and then put it back in but don't connect the connector. this should let enough air past to start and drive normally, but since there is no iacv your engine rpm's will raise as it gets warmer.

These are mostly for tests, without an IACV its hard to balance a cold idle that will not stall out and then have a warm idle that is not crazy high up there.
Thats why most with no iacv leave the warm idle a little high but reasonable ~1200 or so, and use the foot to warm up the car when cold starting even with the raised warm idle, you may only get a 800rpm cold idle if that so you have to use the pedal to open the throttle up some or else it may stall out on you or shake alot cold engine like more rpm's like stock.

 

IAC valve is your problem if your ecu is working properly or has been fix.

my car does the same every morning.

here is what youcan do to find find out if its the iac valve .

remove the hose off the aic valve , and if you hear the iac sucking air then it's not the valve if is not then it's doing what ali had said.

what Ali said is 100% correct.

i like your persistance!

SC400 ecu are just like the 1jz ecu burnt capacitors etc...

gL man and hope you figure it out.

 

yeah what quick said is a good test pull the hose off and see how much air its sucking it should be alot.
Also, Im looking at your picture of the valve not extended and it may need to go further down, thats the position it lets the most air in, so double check it wont go further down try some wd40 to loosen it up, or maybe even just replace the iacv, best bet is a junkyard or car parts online.
IMO the only 2 things that need to be done to an iacv is to hit that gold shaft with wd40, turn the iacv back and forth until it turns buttery smooth, clean off the top part and put it back in. I don't separate the base from the rest of it anymore.

 

Well. It seems it is TPS related. I unplugged the TPS and started the car. Fired right up and went straight to the 1kish rpm idle like it should at cold temps. So now I'm trying to adjust the TPS correctly as per the TIS manual. It's just a pain in the *** trying to get the feeler gauges into that cramped space and then trying to maneuver my multimeter leads when I can't even see what I'm trying to connect. Using a mirror helps, but I SUCK at working through a mirror image. Now it's just too damn cold so I'm giving up until tomorrow, hopefully it warms up.

As for my IACV, I'm very certain mine is fine. I tested it as per the manual and it moves just like it should. If the weather cooperates, I should have the SC running smoothly by tomorrow. Wish me luck!

 

I was just about to say tps after reading your previous post. The fact that the car was working fine and then started tripping out without touching the tps means it's probably bad. They don't just go out of adjustment you know?

 

I am ashamed to say that I actually did mess with the TPS. It was really just out of alignment haha. BUT:


AL FIXED. Got the TPS adjusted as per specs, she runs great. Still on open cat right now, so super super loud. But I don't want to put the midpipes back on because the only point they are supported is where they bolt on to the cats. The rest of it just hangs there, I feel that's no bueno. Once I get the rear exhaust sections fixed, I'll put the whole thing back on.

Thank you everyone for the help and tips, really appreciate it. Now, ONTO THE SUPRA!!!

 

Very good ! Glad you got it working .

 

yeahh buddy them plugs need replacing and I'd clean that iacv if I were you. perhaps something got loose so also check your vacuum lines. all of them. and look into getting new cats or check your headers for even the slightest bend, you never know.