Cold Start Concern

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Nov 12, 2012 | 02:20 PM

Finalatom

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Instructor

Joined: Apr 2012

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From: Tucson Arizona

Cold Start Concern

I have a 96 C4 20K miles on it with and LT1 engine automatic. It always turns over instantly with no problems. A few weeks ago I was in Colorado. It was around 32 degrees in the morning. When I went to start my car and it kicked over, then drop it RPMs for a second almost like it was going to stall then the choke kicked in and it idled fine. No other issues for the rest of the day. The next morning it was 32 again and the same issue on initial start then again no more problems. I came back to Arizona and forgot about it until this morning when it was 35 degrees out. Same start issue. Has anyone experienced this?

Nov 12, 2012 | 06:56 PM

93Rubie

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Joined: Sep 2010

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From: Indiana PA

Choke? You mean Idle Air Control or IAC for short. It maybe is sticking?
Only way to really tell is test it or get a scan tool and watch IAC counts on start up making sure they are in spec.

A good throttle body cleaning never hurt.

Nov 12, 2012 | 08:38 PM

Finalatom

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From: Tucson Arizona

Ok, IAC. How do you test it and what is a scan tool? And how do I clean the throttle body?

Nov 13, 2012 | 08:48 PM

93Rubie

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From: Indiana PA

If you don't have a FSM (Factory Service Manaul) it is going to be difficult to test the IAC, you need the wire colors and such. I have no idea what they would be on a 96.

A scan tool reads codes from the various modules (computers) in your car. It can also show engine data such as RPM, MAP data, knock counts, etc...

This is the one I have. Its a entry level Profressional Grade scan tool.
http://www.nemisysotc.com/

Makes diagnosis of computer controlled vehicle much easier. You can see what the ECM is seeing and doing.

I would start with cleaning the throttle body. Pull the air tube going into it. Then take a soft bristle tooth brush and a little carb cleaner on the brush. Then open the throttle blades and scrub away the carbon build up. The IAC passage is directly in the bottom middle of the throttle body as viewed from the front.

Nov 14, 2012 | 08:57 AM

Finalatom

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From: Tucson Arizona

Thank you.

Nov 14, 2012 | 07:16 PM

93Rubie

Safety Car

Joined: Sep 2010

Posts: 3,752

Likes: 190

From: Indiana PA

Just don't take what I said as gospel a lot of things can cause issues. I just gave you my gut answer based on the info you posted.

Good Luck

Nov 15, 2012 | 05:37 PM

pcolt94

Le Mans Master

Joined: Jan 2006

Posts: 5,620

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From: Orlando FL

If ever I seriously suspect the IAC being bad, I just replace it. You can check the counts from the PCM but don’t really know if the IAC is sticky or responding correctly.

For a relatively not to expensive part, I don’t clean them anymore, they never last for me. But I may clean it just for diagnostic purposes. They do go bad and many times there is nothing to see or measure that would indicate a problem.