I just installed a new 355 into my 91 rs. I start it up and it idles like dog crap when it's cold. it idles like dog crap when it's hot. However when under load it will perform very nicely. When it comes up to operating temp the service engine light comes on. I scanned the system and found a code 42.
EST low voltage or
ESC faulty operation
I didn't get this code when I had the old engine in the car. I disconnected my EST to set timing and since then have disconnected my battery and cleared the codes. this one still comes up and only comes up when the engine reaches 220 on my temp gauge. I never played with the ESC. I did replace an eye-connector on a ground wire for the ECM that bolts to the back of the head on the left (drivers) side. it was a light tan wire with a black stripe. I suspect this is the ground for the EST connector but, I don't know for sure and I don't know if this could be causing the problem.
Could this be a false code due to a bad O2 sensor?
Keep in mind it runs the same in both open and closed loops.
Where do I connect my meter to find out if my EST connector really has low voltage? How much voltage is it supposed to have?
How can I check my ESC module to make sure it is ok?
Lastly, what does the ESC look like? Is it that flat, rectangular sensor located right in front of the relays with about 5 or 6 wires coming out of it?

Help.

 

well it sounds like it shouldnt be that hard to fix. first of all, 220 is way to hot for most normal driving. in my opinion, id go with a 160* t-stat to cool that bad boy down. but for the idle problem, have you checked the IAC? if it was somehow stuck shut it would kill your idle. i had the same problem on my iroc after the 355 swap. as for the ESC, i dont know a whole lot about that but i do know that the electronics on our cars were built with 80's technology, so i wouldnt be surprised if it was acting up a bit.

 

well I know why it runs hot. that is an unrelated problem because this happens all the time. see the 305 i had in there had water jackets in the heads to circulate in front of the engine only. the rear water jackets are blocked off on the old heads. however, the new heads I put on it have water jackets in the front and rear opened up and the intake matches. so where as before antifreeze was dipping down into the engine, coming back up into the intake, circulating through the intake and going to the radiator. now it's dipping down into the engine, coming back up into the intake then going back down again in the rear, through the engine and back up the other side of the intake in the front...plain terms. instead of it going into the engine, getting hot and coming back out, it's going into the engine, coming out hot but, going back in again getting hotter. I have a 180 t-stat. I think I may need a higher flowing waterpump for this motor. and possibly a dual fan.

 

I checked the IAC with my multi meter and it passed with flying colors.

 

hmmm... well the IAC is the usual suspect but with that possibility ruled out id check TPS, and maybe the idle screw. other than that, just double check that your timing is ok. if that doesnt do it, its time to grit your teeth and accept the fact that you have a vaccum leak.....

 

well I actually replaced the tps before the engine blew because I was getting a SES light but it wasn't leaving a code plus I was experiencing some surging but not like this. I'll check it anyway but, I don't think that's the problem.

As for vac. leak....unless I have a bad hose somewhere I don't think so because I just rebuilt this motor and I was sure to use a little RTV on the corners of the intake and china wall gaskets/seals. I will check with a vac. gauge to make sure but, if it comes up 20... I still have a problem (obviously) lol

Thanx for the ideas