LT1 High Idle

**ReidB** · 09-12-2016

Hello.
OK, so I'm a noob from the land of carbs. As some of you know, I have a 94 CAD LT1 transplanted into a 95 K2500. Nothing fancy, just trying to sort out everything.
Having issues with trying to get an idle below 1500.
Over the weekend I found a vacuum leak, cleaned the throttle body and IAC, replaced the TPS. Put it back together, and wala... now it freaking idles even faster.

I'm using EEhack and am still fairly clueless. I tried to attach my last run but it won't let me. If someone could take a look at it and give their thoughts, I would be forever grateful.
Thank you!

**91ss** · 09-12-2016

Having those spark plug wires so close to the ECM wiring is not helping. Probably getting a good bit of inductive coupling to the low voltage signal wires running to the ecm.

**ReidB** · 09-12-2016

Good point. Thanks.

**91ss** · 09-12-2016

Originally Posted by ReidB

Good point. Thanks.

Take a look at the vacuum elbow at the TB on the passenger side. It's the one below the bigger line that goes to the valve cover. A common one to get brittle. Just noticed mine last weekend. The good fix is to use an old spark plug boot off the original 7mm wires. Which i just threw out a couple months ago... :( As a temp, i just coated with some black rtv.

**ReidB** · 09-12-2016

Yep, that elbow was split. Already plugged up. I think it may be the iac but Im getting tired of throwing parts at it without being sure. $$ I can get idle down by partially covering the triangular air opening between the throttle blades with my thumb.
Anyone know how to check the iac? It ohms out ok but it would be nice to be able to power it open and closed and check the plunger depth vs the bore depth. Seems like 5v on rt pins and lt pins would do it but not sure. Thanks.

**ReidB** · 09-13-2016

Originally Posted by ReidB

Yep, that elbow was split. Already plugged up. I think it may be the iac but Im getting tired of throwing parts at it without being sure. $$ I can get idle down by partially covering the triangular air opening between the throttle blades with my thumb.
Anyone know how to check the iac? It ohms out ok but it would be nice to be able to power it open and closed and check the plunger depth vs the bore depth. Seems like 5v on rt pins and lt pins would do it but not sure. Thanks.

Here's a screenshot of the data. Thank you for looking.