Hi guys, first post on CL, long time lurker, and owner of a 92 sc400 and 92 sc300

So the 92 Sc400 is my daily, it has 145k. Bought the car a couple months ago, ran fine for a while and then one day all of the sudden i go to start her up and she wouldn't fire. It cranked fine, so I tried giving it a little throttle and it turned over and fired up but then died as soon as I let my foot of the pedal. After doing a little research I found that my issue is likely the IACV. I replaced it with a refurbished IACV from Ebay, being that the only new one I could find was $852 and not OEM but an aftermarket replacement.

Upon replacing it I started the car and the idle was very high, around 1800 rpm. I let it sit for a while, and the idle evened out at around 700 rpm, which is good. Took it for a drive, got some gas, turned her back on and she ran like a champ. Drove around a bit more, and...awesome, seems like the issues are gone.

I go to start her up for work this morning, she started up just fine, was running good. Then at a stoplight I noticed the idle was low. Then at the next light she stalled. So I drove her the rest of the way to work keeping my foot on the throttle and shifting into neutral, using my left foot to brake and my right foot to manually keep the car in idle range while in neutral.

Now she's right back where I started. Any help would be greatly appreciated guys.

Also I forgot to mention that, once I get the car up to operating temp it idles totally fine. After work today I was messing around and after holding the throttle at idle for about 25 minutes slowly let my foot of the throttle, the idle would drop slowly and the kick back up slight until it gets to right around 700-800 rpm. Also the car cranks over just fine once it's at operating temp, after getting it to idle in the manner I mentioned before, i turned the car off and started her back up and she fired up and immediately went into idle about 700-800 rpm.

 

There is a variety of things you can do. I've had similar issues, but I've also had long crank no start. The first thing you can try is bypassing the fuel ECU. Then try the fuel relay if the low idle stalling returns. If that doesn't resolve it try replacing the big green relay. My fuel regulator has been replaced recently so I haven't bothered checking this yet, but you may try and looking at it as well.. last but not least try getting a resistance check at the ECM/ECU terminals to the fuel pump and from the fuel pump itself.

I'm sure someone else will chime in and correct me or lead you in a better direction.

 

I will try out your suggestions today and see how it works out, thank you. I appreciate any help I can get.

 

So yesterday I tried bypassing the fuel ecu to no avail, car still had the same problem. I decided to try and get the car up to temp and get it idling right and then just unplug the IACV electrical connection. So far the car has run fine since I did that. Idles a little low but never stalls. Would this indicate that the refurbished IACV is no good, or do you think i should continue with the fuel troubleshooting?

I don't really want to spend close to $900 for a new IACV, but if I have no other choice to get the car running right then I'll just have to bite the bullet.

 

Have you tried rebuilding your old one?
cartunenz on YouTube has a break down. I bought the bearings to do this same thing but it has stopped.. so, I'm looking at other avenues as well