1994 k1500 350 swap has idle issues

[94shortbed]

hi everybody. like the title says i did a 350 swap in my 94. it was originally a 305 but i swapped in a 350. the 350 has a 20 over bore and a comp lw end cam. nothing wild its basically stock. i took the 350 out of a junk truck and completely rebuilt the motor. everything is pretty much new. i even ripped the ecm out of the junk truck which was also a 1994 1500. my issue is the idle. when it starts up it has a really low idle. but it does go up with some time. maybe a minute or 2. im not sure what is wrong since the idle air control valve is new. any advice or help is greatly appreciated. thanks guys

 

[Swims350]

other then idle does it run and drive good no missing or anything?

 

[ChrisAU]

CTS in the manifold IMO. Idle should be higher at crank and for a minute or two until warm, not lower.

 

[94shortbed]

other than idle it does run and drive fine in my opinion. and could you elaborate on the CTS issue

 

[ChrisAU]

Coolant Temperature Sensor. That is the sensor that tells the ECM to command a high idle when the engine is cold to warm it up.

 

[94shortbed]

ok i will replace that as well. just hooked a scanner to it and the computer shows an IAC valve code. which is new so im a bit confused now

 

[94shortbed]

also even when the truck is warm it idles really low and takes a while to get the idle up. the scanner also showed a MAP sensor code so i replaced that. made some improvement but like i said even when its warm the motor takes a bit to idle and even then it still seems a bit low. i mean ive only put 50 miles on the motor so far. could the ecm not have reset yet? if so about how long does that take? i mean i can drive it its just at startup is when it worries me.

 

[Swims350]

you need to let the IAc set itself if that's not been done it should be, you should also clear the computer when you change sensors and such.

 

[94shortbed]

ok can you tell me how i reset these things?

 

[Swims350]

computer gets reset by pulling the ecm fuse in the fuse box or unhooking the battery.

the IAC I forget how it gets reset.