Coolant temp sensor??

[Jersthecool]

So I know there's 2 coolant sensors, the ecu one and the cluster one and my cluster one has always kinda bounced around I think just because a loose connection or it was starting to die. Then the other night I started the car, let it warm up and hit the bee r rev limiter to show some friends and didn't realize until I went for a drive that the cluster temp wasn't working. So the next day I start the car and the rpms go up to like 1500 when it's warming up and they kinda drop eventually but the temp gauge still doesn't do anything, so driving it around randomly the temp will kinda go up a tiny bit around the C but the engine is definitely hot. So randomly it will go up and down only a little bit, then I went on the highway and it will go up to half where it's supposed to be and won't move but here's where it gets weird. If I pop it into neutral the rpms will idle at around 850 where they normally do and it's fine then when you sit there the temp gauge will keep dropping slowly and the rpms will go up and eventually idle at around 1000-1150 or so and I've realized when the temp gauge isn't where it's supposed to be at half it's being a pig on gas!

On the highway the gas mileage was good, pulling off the highway and driving around the gas mileage was good, then when you're driving as soon as soon as that temp gauge starts dropping the gas mileage gets really bad. So obviously the temp gauge for the cluster shit out but is it just a coincidence the one for the ecu shit out at the same time causing it to think it's running cold and dumping more gas into the engine or should I be looking at something completely different?

[fliprayzin240sx]

Check the wiring first. My current S14 did that but turned out I had corrosion on the sensor and connector. Cleaned out and fixed my issue. Then a few months later did it again but this time, the sensor is dead.

[Jersthecool]

Yeah took a look at it and the metal part that the wire connector slides onto is really loose and doesn't seat well on the sensor so I think that's what's making it read funny. Just super weird the one for the cluster is actually affecting the idle thought it would be the other one but whatever I've heard the KA ones fit so I'm gonna replace both of them asap.

[TheRealSy90]

You want to match the cluster sensor to the cluster you have. For instance I have a redtop sr20det, and i'm using a DOHC KA cluster. So I use a dohc ka temp sensor.

[Jersthecool]

Alright so I went and bought a new cluster temp sensor, pulled the old one out and the metal ring had a piece missing so it was wiggling around and wasn't making good contact, put a new one in, topped up the coolant and fired it up. Now I think I just need to bleed the system because it heated up very slow and the needle didn't move with the heat on full blast and when I parked it and blasted the heat the temp actually dropped slowly, but the engine and rad are nice and hot.

Back to the original problem though, even once the car heated up and got to it's regular running position on the needle the idle still stayed high and never dropped down to 850 like it's supposed to, it's stayed at around 1200-1300. Sure I didn't mind spending $20 on the gauge temp one because it was broken and never worked properly but I really don't wanna spend the $50 on the ecu temp one if I don't need to. Anyone know if it really does sound like the ecu coolant or is it something entirely different?


EDIT: Just thought I'd add don't think it's a vacuum leak as my vacuum is still -15 as it was before as well could it possibly be my IACV? Seems kinda weird it was always fine then all of a sudden I hit this limiter and it shits out, I also cleaned it with carb spray when I pulled it off in winter of 2012 so I can't see it being that dirty already. It's too bad I just got my wideband installed after this problem started because, moderate gas and WOT the air/fuel is good but as soon as I apply light gas or have it idle it's running really rich around 11.8-12.4 and I have no idea what it was running before but I don't think it was running this rich.

[racepar1]

It could be the temp sensor for the ECU. 15in of vacuum is a bit low though, it could still be a vacuum leak. It could also be the TPS. It could be the AAC valve. Have you cleaned the AAC valve yet?

[Jersthecool]

I've always run 15 vacuum and never had a problem. Not too sure about the tps and what is the AAC? In my last post I refered to the IACV if that's what you're talking about.

[fliprayzin240sx]

You want to match the cluster sensor to the cluster you have. For instance I have a redtop sr20det, and i'm using a DOHC KA cluster. So I use a dohc ka temp sensor.

Well, the gauge water temp sensor is specific to the chassis, not the engine. So if you have an S13 cluster/chassis, you want an S13 water temp sensor. S14 for an S14. KA and SR are the same.
Alright so I went and bought a new cluster temp sensor, pulled the old one out and the metal ring had a piece missing so it was wiggling around and wasn't making good contact, put a new one in, topped up the coolant and fired it up. Now I think I just need to bleed the system because it heated up very slow and the needle didn't move with the heat on full blast and when I parked it and blasted the heat the temp actually dropped slowly, but the engine and rad are nice and hot.

Back to the original problem though, even once the car heated up and got to it's regular running position on the needle the idle still stayed high and never dropped down to 850 like it's supposed to, it's stayed at around 1200-1300. Sure I didn't mind spending $20 on the gauge temp one because it was broken and never worked properly but I really don't wanna spend the $50 on the ecu temp one if I don't need to. Anyone know if it really does sound like the ecu coolant or is it something entirely different?

EDIT: Just thought I'd add don't think it's a vacuum leak as my vacuum is still -15 as it was before as well could it possibly be my IACV? Seems kinda weird it was always fine then all of a sudden I hit this limiter and it shits out, I also cleaned it with carb spray when I pulled it off in winter of 2012 so I can't see it being that dirty already. It's too bad I just got my wideband installed after this problem started because, moderate gas and WOT the air/fuel is good but as soon as I apply light gas or have it idle it's running really rich around 11.8-12.4 and I have no idea what it was running before but I don't think it was running this rich.

Where did you buy the water temp sensor from? Also, what chassis is this for? If you got the sensor from Autozone, they only list PN for both S13 and S14s. So if you buy it from them, you could be running an S13 sensor into an S14 cluster and it will read higher than it really is.

[racepar1]

I've always run 15 vacuum and never had a problem. Not too sure about the tps and what is the AAC? In my last post I refered to the IACV if that's what you're talking about.

The IACV is NOT the primary idle control valve. The IACV is the long one that is held on by two bolts in the middle. Also the IACV is pretty much wide open inside and has little chance of clogging. The AAC valve is the primary idle control device. It is mounted on the base with the FICD valve and the idle screw. I have had great success in fixing idle problems by simply completely dis-assembling that valve assembly and cleaning the piss-shit out of it. Of course you then have to re-set the idle via the idle screw. The passages are very small and get clogged up with carbon. This can cause the valve to stick and all sorts of idle issues. THIS is the AAC valve assembly:

Nissan OEM S13 SR20DET Idle Air Control Valve AAC IACV (http://www.frsport.com/Nissan-OEM-S13-SR20DET-Idle-Air-Control-Valve-AAC-IACV_p_1123.html)

Just to be completely clear, the coolant guage has NOTHING to do AT ALL with the coolant temp that the computer sees. Those are two completely different circuits...

[Jersthecool]

Yes I bought an s13 KA one from the same year 240 I have, when the temp did eventually rise it was where it was supposed to be not high or have a weird reading. However I tried to bleed the system, got air bubbles to come out and drove to my friends house fine, parked it for 3 hours, then started it let it idle for 2 mins, then drove for around 10-15 mins and it still wasn't completely heated up not too sure what that's about now, hopefully it's not the thermostat just changed that last year too.

Thank you for clearing that up I thought the whole thing was just called the IACV. Well yes I did remove the whole thing and cleaned the spring part as best as I could with carb cleaner last year. I know after I cleaned it though it still didn't look the cleanest and I'd pull it off again but it was a huge pain in the ass even with the manifold off the engine. I've heard of people removing the screen and spraying in there maybe I'll try that and see.


EDIT: Just thinking now though even if the IACV or AAC is stuck and causing the idle to be higher will that affect my AF ratio?? When I was driving earlier for a little bit cruising and idle was actually a bit better at around 13.6-13.8 instead of being super rich at like 11-12. That's why it seems like the coolant temp sensor because wouldn't it thinking it's cold actually make it idle higher and dump more fuel to try and warm it up?

[TheRealSy90]

Well, the gauge water temp sensor is specific to the chassis, not the engine. So if you have an S13 cluster/chassis, you want an S13 water temp sensor. S14 for an S14. KA and SR are the same.

That's weird because when I first swapped my sr20 I. I had a sohc cluster and it did not read correctly, when I swapped to the dohc cluster the temp the read correctly.

[Jersthecool]

So bled the whole system and it still takes forever to heat up I'm talking like 20 mins driving and even at that it barely blows warm air and if the heat is completely off and it's just idling the temp will actually go down because the fans are cooling it so much. Definitely sounds like the thermostat is stuck open but could the coolant temp sensor cause these issues at all because the idle is still higher even when it "warms" up and the thermostat shouldn't affect that at all.