[B]FIXED FINALLY[/B
Thought I would update to help others if they come across the"warm weather low idle"
Trying to fix my low idle since last spring cleaning,checking,replacing!!To find out (not visible)there was a fine tear from the rubber coupler on the intake!!! I checked and checked,felt nothing at the time but,decided to disassemble everything and saw a fine tear underneath the lining of the coupler which explains it getting soft and brittle in the heat throwing off the idle.It fixed my low idle,quiet blow off valve sound during shift,and smoother ride down hill on the hwy(less sensitive to throttle)......finally!!



]I have a stock 93 manual SC with 140,XXX miles.Since the weather has warmed up the car has had a couple very low(200rpm)rough idles at start up like it's about to stall.Third day it's happened and progressively gotten worse where today it about stalled had I not gave it gas.When I hit the gas the needle just bounces back down/up a couple times.I have also noticed my gas mileage in the last four years has dipped down a little to 18-20 mpg on a good day.I have kept this car up to service and the most recent has been the up/downstream o2's replaced a coupe months ago.There's also a noticeable smell of gas/exhaust fumes at start up.Any ideas?Fuel filter?Cat?

Thanks

 

The smell could either be 1, running lean or 2, failed Y-pipe gaskets. Could be cats as well

 

Bump....for a solution?I cleaned the IACV with no progress.

 

Im guessing sc300 from the manual comment, if thats the case I have had a similar problem with the cap and rotor. If you don't replace them at the suggested intervals that can eventually happen. funny thing is mine did that at 135k.
could also be something else, but if you have never replaced these I would go ahead and do so with some toyota parts.
tell them you have a 94 non-turbo supra and you should save over going to lexus.

 

Yeah I replaced my cap/rotor at 130k.Wondering if the fuel filter might have something to do with it?I'm sure the previous owner never replaced it.

 

I also have an SC300 manual SC with a stock engine/trans. I have had the same issue at startup on occasion in warm weather. I haven't solved it yet but a few blips of the throttle seems to cure it. I chalked it up to an air pocket in the coolant system since I had a small leak from one of my freeze plugs that I just had replaced along with a coolant flush. I haven't had it come back... yet.

In my case I've replaced or am within service intervals with:
plugs
distributor cap+rotor
new upstream cat
#1, #2, and #3 oxygen sensors
new fuel filter

My downstream cat is original and I suspect is getting clogged because the car still smells like fumes a bit until it's at operating temp. Do bad cats cause this symptom?

 

Yeah I still have that exhaust fume smell at start up for the last couple years it has slowly gotten worse and is very noticeable in parking decks.I'm thinking the cat might be bad but,it still passes emissions?I've done all the services except for the fuel filter and cat.What I'm trying to figure out is what is it that the hot weather change makes it idle low at start up and stall?

 

I'd suspect your IACV but you said you've addressed that. I personally have never had a stall out with this issue. Have you considered your injectors? I have yet to service mine but I've wondered if their age (never replaced) might contribute to this or not.

 

not sure about the smell that could be the charcoal canister up in the bay also.
I think the cats would fail emissions before they clog up completely.
probably something simple, have you done the plugs.

 

I have done the plugs and wires about 10k ago.Yesterday I checked the TPS and this morning it ran very bad not knowing now that I re-installed it incorrectly.So I played with the TPS and turned it all the way counter clockwise to just get the screws on but,the issue is still there not as bad though now it's only when I stop at a light it dips 100-200 rpm and stalls so I have to have the a/c running to keep it stable.Can I adjust the center nut where the points meet the tps to even the idle?

 

Make sure you set the TPS to the correct place. Should read 0:00 ohms (infinity or open circuit) with a feeler gauge the size of a credit card between the throttle lever. You can't just switch the TPS in circles and expect that to do. You have to set it, so you know it isn't bad, or it is for that matter. GL.

 

With the feeler gauge either on .40-.65 it stayed and is maxed counter-clockwise at 0.6 ohm which recommended is below 2.3 or less.My VT1-A-E2 is set at .436 ohm recommended 0.2-0.8.It's now driving where I come to a stop light and put in neutral it jumps down to 100rpm and stalls so I have to have the a/c running.When you take the tps out and look inside the intake part it's attaches too are the two pins suppose to be at 8/2 oclock?

 

I also just got a code 31 MAF today but,it seems clean.I diagnosed if it was bad by unplugging it and starting it but,that made it worse by starting and quickly dying so that's not it.I also let it idle in my driveway and maybe after 1-2 min it would drop and start idling low(200 rpm)Any other ideas?

 

Sounds like its close enough then. .436 is almost 0 ohms so thats good. With he feeler gauge at .65, its .1 away from what it is supposed to be so thats fine. Sounds like you ruled out the TPS.

I dont remember if the pins were 8/2 oclock or not.

Make a list of things youve replaced or set. Sorry, on the ipad andits nasty to tpe on it lol!

GL!

 

Also to add while diagnosing code 24-31(intake temp/air flow)=MAF I started it let it sit for about 3-5 mins once it got to temp the idle dropped but,when it did I ran compressed air with the intake filter off and it shut off right away?So I am assuming the MAF works?I also carefully ran a heat gun on the MAF and the filter to see if it changed anything considering it happens in hot weather but,with no change.I then unplugged my fuse and later started it and it idled fine but,it was already night and cool so I will try again later today when the weather is warm.