1JZ Idle Drops With AC on Then Stalls Out

[cyrusthegreat]

I did the R-134a conversion this past week and I'm happy to report that the A/C now blows cold air. However as the title states, my idle drops to about 300 - 400 then stalls out while idling. Otherwise my car runs great without the AC on. I've tried searching and I found some posts regarding the IACV but I'm not sure this will fix the problem, but I'm willing to try cleaning or checking it. I called Aaron at Driftmotion (did my swap years back) and he thinks that it's the signal from the compressor to the ECU. I am a super newbie at all things electrical and I now have moved far away from any shops that I trust to do this. Can anyone tell me how to check this? I do have a voltmeter and my glove box is already off. Any advice or links to info is greatly appreciated.

To be more concise, I need to know how to test if my ECU is getting the right signal or if it is even wired up. So, I'm hoping that someone can tell me in very simple terms where on the ECU I should check for a wire/pin/connector and perhaps how to test for resistance or if its getting electricity. I've always struggled with electrical work (including understanding wiring diagrams) but I am learning more with each project I tackle. Thank you SupraMania Electrical Gurus in advance.

Terms I tried in the 'Other Engines' Sub Forum
AC, A/C Air Conditioning, Idle, Drop, Up, IACV, Stalls, Dies
I figured this is the right place to post this since I have a TT 1JZ-GTE

 

[tlo86]

im curious if you ever got this resolved? these posts get old fast...

i highly doubt its a wiring issue right of the bat.. as nothing would make the car die just make the a/c not work.

but you converted to r134a how did you do this? what are all of the steps you took when doing it...
if i were to tell someone to do it..

you would completely flush the system (either have it professionally done or use a can)
get all of the old oil out (compressor and flushing the lines)
change the receiver drier (old oil here as well)
change the seals (by now the material of the seal doesn't matter they are gonna leak )
add oil either to compressor, receiver drier or both just make sure you use the right type and right amount.
change the fittings on the lines
vacuum the system for an hour or two
then recharge. ( always use a manifold dont just use the cheap can taps they are designed as a shitty temporary fix since nothing will keep the ac from draining except stop leak and that just adds more problems anyway.. and you cant properly diagnose a/c issues)


if anyone experiences this same issue first....
make sure charging system is 100% battery test / alt test this is free at any parts store. (low volts = dead car especially when accessories are turning on you haven't used yet)
this includes the battery cables - i always add an extra ground to the chassis usually 4ga and i replace the power cable at least once every 30 years

make sure the a/c clutch is properly engaging and disengaging.(you should be doing this with any ac job though right? clutch not disengaging = extra power draw and a nice smell of burning a/c clutch.. plus it'll make all of the paint on it go away also signs of an improperly shimmed clutch if it just half spins btw and gets hot burns up etc)
test your fuel pump pressure.. again a free rental tool. (low volts = less volts going to the fuel pump = less fuel pressure)
test the fuel pump relay or just replace it ( i have seen resistance build in old relays to gradually go out rather than quit working right away these are very universal relays 15$ or less anything else you are buying clips and crap you dont really need when function is the same)
make sure the fuel pump resistor on our cars (most cars dont have this) is not creating TOO much resistance... this checking voltage *too* pump and making sure its enough.

 

[hvyman]

Who did the wiring?

The Ecu has 2 different pins that need to be used in order to get idle up.

 

[cyrusthegreat]

Thanks for the responses tlo and hvyman, I was beginning to think that no one would ever respond to my post.

I have not resolved this issue yet. I pretty much followed the steps in this guide.
http://www.supramania.com/forums/showthread.php?157624-DIY-R-12-to-R-134a-Conversion-(How-To)

I did flush out the old oil with a flush gun, changed all the o rings and vacuumed out the system and let it sit overnight. No leaks. I also switched out the schrader valves. I added all my oil through the compressor before putting it back on. My battery does seem to discharge but I live in the Colorado Desert in CA and this heat seems to be hard on batteries, I also haven't been driving the Supra as much as I should. I did put in a new one about 6 months ago.

No burning smell and the compressor turns on and off. To test and fill my A/C system I put a card in the throttle plate to hold the RPMs at about 1200. I like the idea of checking my alternator and fuel pump and relay. I don't think this is the problem but I feel it's still something I should check since my car is 27 years old. My car usually only idles at about 500-600 rpms but when the compressor kicks on, it drops then dies... I'll check out your recommendations when I have some time and report back. Today I'm going to install some Tokico Illumina 2s for the front end. My shocks are blown and I can only afford the front end for now. I did get some new tires recently though... slowly but surely I will hook this car up.

 

[cyrusthegreat]

Hvy man,

The 1J swap and wiring was done by Driftmotion. I tried taking a look at the 1J ECU with my buddy that knows more about wiring and we used this diagram.

The diagram didn't seem to match the ECU?? Next time I'm in there I can take a picture to show you.

I'll probably just take it back to Driftmotion and have them fix it for me. Unless you think this is easy enough for me to handle? I would def need some hand holding. Maybe they'll hook me up, since it didn't get wired up during the swap. He said something about not being able to test it, since there wasn't any refrigerant in the system. So frickin hot out here, I've hardly driven the Supra. A/C would be fine on the freeway though...

 

[tlo86]

if they were responsible for the wiring and it doesnt work its on them to get it right. a battery can sit for 9months according to east penn before it needs a test and charge... assuming there is no discharge on the battery. how many miles did you put on it before the ac system work
?

 

[cyrusthegreat]

Not that many, less than 500. I borrowed a battery charger from work and it's up to 100% now. It was down to 70%.
Yeah I agree with you, let's see if they do too. The work was done over 5 years ago. Once they fix it, I'll ask what was up and report back.

 

[emiliorescigno]

I'm having the exact same problem, but I don't have any of my wiring/notes with me at work. I've been discussing it with toyotanos as well - I'll check back in here later today.

 

[emiliorescigno]

If you're still watching this thread - I did end up fixing this problem before I sold my car.

I wired in a relay to switch the AC pin on the ECU to ground when that wire from the chassis sees +5v. Worked like a charm.

(I can't remember exactly which one it was off the top of my head, but I'd guess T7 on your diagram)

 

[hvyman]

the a/c pin gets switched to ground from a relay. what controls the relay?

 

[emiliorescigno]

the a/c pin gets switched to ground from a relay. what controls the relay?

On this page: Pin 11 on the AC amplifier marked as "TO TCCS ECU A/C"

http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=143

When that pin goes to +5v - pin T7 on the above ECU should be put to ground. Presto - A/C idle-up!