Function of air intake sensor?

[CaptCaper]

I have cold idle issue. Eractic. Goes from 2k down to 1200 or 1300 then back up. It stalled a couple of times. Once starting to get warm and all day long it runs and starts great. No codes ever. Or engine light. Been a while it's been doing it.
I was looking at this part #14 in attached picture that states it's a air intake sensor. What does it do?

 

[Srxspec]

Sets the fuel map for the ecu. The ECU uses air intake temp, barometric pressure, and manifold pressure to determine what fuel mapping it should use. I doubt the air intake temp sensor is causing your idle surge.

 

[Stubbs]

Smart money says you likely need to check the valve lash and adjust as needed. I’m thinking you’ll like find several that are tight.

 

[CaptCaper]

Sets the fuel map for the ecu. The ECU uses air intake temp, barometric pressure, and manifold pressure to determine what fuel mapping it should use. I doubt the air intake temp sensor is causing your idle surge.

thanks.. someone mentioned there is a part that has a spring in it or wax in it that will melt when warm in the case of the wax mention or the spring part somehow will effect cold idle. Do you know what part they were talking about?

 

[RobX-1]

someone mentioned there is a part that has a spring in it or wax in it that will melt when warm in the case of the wax mention or the spring part somehow will effect cold idle. Do you know what part they were talking about?

Do you mean this post I had quoted back in Dec of 2023 regarding someone having a weird cold idle issue? If so, here's the exceprt and the link to the original post.

Yes that is the thermowax, the 2 lines that hook up to it are coolant lines. When the engine is cold it allows more air to bypass the throttle plates through the IAC. As the coolant warms up the wax, it slowly closes off this extra air, then your idle adjustment screw takes over. Your throttle plates should be completely closed when at idle, If they are open slightly then your issue is either the linkage holding them open (ie) cable is tight, or the shaft that your throttle plates are attached to are starting to get stiff (usually caused by corrosion) and not allowing the plates to close. If the plates are completely closed, then the engine is getting too much air from another source such as the thermowax or cracked TB boots, gaskets or loose clamps. I am referring to the rubber ones that connect the TBs to the engine. The thermowax has been an issue with motorcycles that have the same setup. With the symptoms you are describing it sounds like the thermowax is causing it, but I would check the boots to rule that out.

 

[CaptCaper]

Smart money says you likely need to check the valve lash and adjust as needed. I’m thinking you’ll like find several that are tight.

Funny thing is a tech guy I talked with said when sled was warm it would have issues if shim job was needed. I read here others had cold idle issue then a shim job and it worked out. Maybe it's best to spend the $800 or so just to rule that out. I only have 6500 miles now. I'm going to try changing the plugs first.

 

[CaptCaper]

Do you mean this post I had quoted back in Dec of 2023 regarding someone having a weird cold idle issue? If so, here's the exceprt and the link to the original post.

That's it. I'll look into this more. His was carburated apex I believe but maybe I have one on my 3 hole fuel injected.

 

[RobX-1]

After posting that link, I realized the OP in that post had a carbed RX-1 and wasn't sure if it was applicable to the fuel injected ones like yours.

 

[CaptCaper]

After posting that link, I realized the OP in that post had a carbed RX-1 and wasn't sure if it was applicable to the fuel injected ones like yours.

I'm looking at a manual and I just got to the part of that part. Idle Speed control unit. It shows how to test it with a meter but it's vague to me. Ha. Also if defaulted replace throttle body..holy fuel inj batman. $1300 or so.

 

[74Nitro]

Wouldn't be a bad idea to check fuel pressure.

 

[CaptCaper]

Wouldn't be a bad idea to check fuel pressure.

Runs like a raped ape when warm. And it doesn't take long to warm up.

 

[74Nitro]

Runs like a raped ape when warm. And it doesn't take long to warm up.

Tight valve lash should affect it more so when hot, not on cold start.

 

[CaptCaper]

Tight valve lash should affect it more so when hot, not on cold start.

And loose valve lash effects cold start?

 

[74Nitro]

And loose valve lash effects cold start?

I highly doubt its loose, but even if it was on the loose side, it would start just fine cold. No effect.