93 LTI Won’t idle when started cold
Thread Starter
Burning Brakes
Joined: Feb 2013
Posts: 769
Likes: 95
From: Central Pennsylvania
93 LTI Won’t idle when started cold
My93 LT1 won’t idle on it’s own.for about the first 2 minutes after starting cold. I can nurse the pedal to keep it running, then I’m good to go. My 93 Ruby starts and runs perfectly. I’ve changed out the TPS and the Coolant Temp Sensor ( one that it mounted into water pump ). Car runs and idles great once it has warmed up. I’ve used the search function on CF and need to figure out the next step. Any ideas?
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,595
Likes: 4,055
From: Cape Coral, Florida
The CTS would be the first sensor to be looked at for any cold start issues...since you're saying it's during the first 2 minutes of startup the car should be in "open loop" at that time so the O2 sensors should not be affecting fueling. In open loop the ECM looks at a few sensors to determine the correct injector pulse until the O2 sensors have been warmed up...your LT1 uses the Intake Air Temp Sensor (IAT) as one of those sensors...if you don't have a scan tool or any type of diagnostic equipment you'll only be firing the "parts canon" !!!
Pro
Joined: Aug 2019
Posts: 596
Likes: 146
From: Minford, Ohio
If you have a laptop computer you can buy an OBD1 cable for $60 and there is free software you can download and run to see all your
sensors' values. If you're going to attempt to fix the problem yourself you will need this setup otherwise you will be reduced to changing
parts!
sensors' values. If you're going to attempt to fix the problem yourself you will need this setup otherwise you will be reduced to changing
parts!
Thread Starter
Burning Brakes
Joined: Feb 2013
Posts: 769
Likes: 95
From: Central Pennsylvania
If you have a laptop computer you can buy an OBD1 cable for $60 and there is free software you can download and run to see all your
sensors' values. If you're going to attempt to fix the problem yourself you will need this setup otherwise you will be reduced to changing
parts!
sensors' values. If you're going to attempt to fix the problem yourself you will need this setup otherwise you will be reduced to changing
parts!
Definitely will get the cable. I got 4 C4’s, of which 2 are LT1’s and 2 are L98’s. Will come in handy. One of my fellow pilots had a CAM’s machine from a GM dealership but he sold it when he relocated to Aruba.
Thanks for the reply.
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
Sounds like the idle air control (IAC) valve on the throttle body. At cold idle you need more air to keep the car running (and fuel) and if the iac valve is stuck shut or the passage is plugged it will not be able to get the air and it may not idle. There is no code set for failed iac so it can be difficult to trouble shoot. Does the idle rpm change when you add loads to the warmed up engine like turning on the headlight or air? If it always drops with loads you should definately look at the iac.
Last edited by bjankuski; Dec 19, 2019 at 05:48 AM.
Thread Starter
Burning Brakes
Joined: Feb 2013
Posts: 769
Likes: 95
From: Central Pennsylvania
Sounds like the idle air control (IAC) valve on the throttle body. At cold idle you need more air to keep the car running (and fuel) and if the iac valve is stuck shut or the passage is plugged it will not be able to get the air and it may not idle. There is no code set for failed iac so it can be difficult to trouble shoot. Does the idle rpm change when you add loads to the warmed up engine like turning on the headlight or air? If it always drops with loads you should definately look at the iac.
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