Questions... temp/idle/sensors

[reichbc]

Cutting right to the chase. I'm asking for serious technicals, as much detail as possible, full signal path, etc.

99 Si.

How does the temperature gauge in the cluster receive it's signal (from the ECU / direct from sensor)?
If it's directly from a sensor, which one and where is it?
Would a short in the wiring cause it to jump up high?
What if I said that the temp gauge moves up and down in conjunction with the bouncing idle caused by my IACV issue?
Videos to follow later.


I also have a high idle problem (IACV circuit failure code), but i think that's cause my TB gasket is loose from taking out a throttle body spacer. I'm getting the new bolts from Honda today. Just replaced the IACV yesterday and it still idles high and pops the code so I'm thinking that the new bolts and a nice snugging should clear that up.

Thanks in advance.

 

[jlicrx]

How does the temperature gauge in the cluster receive it's signal (from the ECU / direct from sensor)?
If it's directly from a sensor, which one and where is it?

direct from the sensor - the sensor is located on the end of the head with a one wire connector - wire color is yellow with green stripe - the sensor next to it with 2-wire connector is the temp sensor for the ECU

 

[joeshmo]

Gaskets can't be loose. I suggest you
1) replace the throttle body gasket
2) Replace the IACV gasket
3) Possibly replace the IACV.

Have you taken out/cleaned your IACV or the contacts for it yet?

 

[jlicrx]

What if I said that the temp gauge moves up and down in conjunction with the bouncing idle caused by my IACV issue?

is your cooling system completely full of coolant with no air pockets - bleed the air out of the system - low coolant level will cause fluctuating idle and cause the temp gauge to go up and down as the coolant isn't reaching the sensor

 

[RonJ]

Any CEL codes?

You also may have a grounding problem for the cluster.

 

[reichbc]

direct from the sensor - the sensor is located on the end of the head with a one wire connector - wire color is yellow with green stripe - the sensor next to it with 2-wire connector is the temp sensor for the ECU

Thank you - i know exactly what sensor you are talking about now and I believe I have the replacement on hand. I wasn't exactly sure so I asked the best.

Gaskets can't be loose. I suggest you
1) replace the throttle body gasket
2) Replace the IACV gasket
3) Possibly replace the IACV.

Have you taken out/cleaned your IACV or the contacts for it yet?

Yes. As I originally noted, I took out a throttle body spacer and the bolts weren't right. I have 4 correct ones installed and the idle problem is GONE. IACV is brand new too, clean and functional. Thank you.

is your cooling system completely full of coolant with no air pockets - bleed the air out of the system - low coolant level will cause fluctuating idle and cause the temp gauge to go up and down as the coolant isn't reaching the sensor

At the moment, it's completely full of straight water which i check every morning and night. I didn't want to go through gallons of coolant trying to pin down an issue that would require me to keep cracking the coolant system. Will replace with 75/25 when I get the issue squared away. Thank you.

Any CEL codes?

You also may have a grounding problem for the cluster.

CEL code only came up (P0505) while I had the throttle body gap due to incorrect screws. That's fixed and no codes now.

As for the short in the cluter, that's another thought I had. I haven't had the chance to dismantle it and take a look at anything. I'm going to replace the temp sender first and re-bleed the coolant system (and a fresh water change) to see if it fixes anything.

Ron, do you have the guide sheet on how to do that properly? I've always been under the assumption that you should park your car with the front higher than the back and crack the radiator cap with the car running to release air bubbles.... am I correct?

 

[reichbc]

Another question to help me learn.

I have a fair idea here, but I want to know if the masses can help pinpoint something I can't.

What different factors contribute to an engine heating up / overheating?
So far I've got the obvious generals; combustion, friction.

Thanks in advance!

 

[reichbc]

Update: Replaced the one-wire sensor that was discussed earlier - the temp gauge is still doing its bobbing thing. At this point I'm thinking short in the wire... either that or air bubbles. I topped off the coolant lines and let it run on an incline with the radiator cap off for a good 5-10 minutes..... still lost here. Looking for anything.