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R32 GTS25 high idle help?

damesta
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damesta Apprentice

damesta

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I made a little bit of a discovery, I figured out that if I let the engine get completely warmed up (like I have to go drive for a little while warm...not just idle until its warmed up), then the idle will drop a few hundred rpm and when I unplug the iacv at that point it has no effect. We are still sitting around 1000 rpm though. Previously I had only been letting it idle until the gauge showed it was warmed up. I also checked the coolant temp sensor voltage and observed it as it warmed up and that was all within spec.

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joshuaho96 Veteran

joshuaho96

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4 hours ago, damesta said:

I made a little bit of a discovery, I figured out that if I let the engine get completely warmed up (like I have to go drive for a little while warm...not just idle until its warmed up), then the idle will drop a few hundred rpm and when I unplug the iacv at that point it has no effect. We are still sitting around 1000 rpm though. Previously I had only been letting it idle until the gauge showed it was warmed up. I also checked the coolant temp sensor voltage and observed it as it warmed up and that was all within spec.

Sounds like it may be a coolant temperature sensor issue then. Either a bad connection or a bad sensor. Verify that the temperature starts off at a sane value in Consult, then verify that it rises up to operating temperature in a reasonable timeframe while driving the car. If you see unpredictable jumps in temperature it could be a bad connection somewhere causing the problem.

GTSBoy Grand Master

GTSBoy

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Th curve of resistance vs temperature for the ECU coolant temp sensor is easily enough googled up. You can measure the sensor direct at its terminal to try to isolate the sensor from wiring problems too.

The slowdown from 1200 to 1000 just sounds like the AAC closing as it heats. I can't remember from previous description....is that in the loop or blocked off? The RB25 integrated unit only has one air inlet & outlet right? With 2 paths through it? Like on the Neos?

Some of the reason for my confusion here is that in your earlier post you said you "completely capped off the cold start valve"......but if there's only one air hose bring air to the combo IACV/AAC then you cap off both. Right?

That RB25DE / KA valve pictured is similar but different to the 25 turbo ones, and I've ever messed with NA engines, so I'm not sure if I'm missing something. Does it also have one of these or something similar somewhere? OEM RB20 RB26 IACV Idle Air Valve - Z1 Motorsports - Performance OEM and Aftermarket Engineered Parts Global Leader In 300ZX 350Z 370Z G35 G37 Q50 Q60

 

damesta Apprentice

damesta

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39 minutes ago, GTSBoy said:

Th curve of resistance vs temperature for the ECU coolant temp sensor is easily enough googled up. You can measure the sensor direct at its terminal to try to isolate the sensor from wiring problems too.

The slowdown from 1200 to 1000 just sounds like the AAC closing as it heats. I can't remember from previous description....is that in the loop or blocked off? The RB25 integrated unit only has one air inlet & outlet right? With 2 paths through it? Like on the Neos?

Some of the reason for my confusion here is that in your earlier post you said you "completely capped off the cold start valve"......but if there's only one air hose bring air to the combo IACV/AAC then you cap off both. Right?

That RB25DE / KA valve pictured is similar but different to the 25 turbo ones, and I've ever messed with NA engines, so I'm not sure if I'm missing something. Does it also have one of these or something similar somewhere? OEM RB20 RB26 IACV Idle Air Valve - Z1 Motorsports - Performance OEM and Aftermarket Engineered Parts Global Leader In 300ZX 350Z 370Z G35 G37 Q50 Q60

 

I already tested the voltage of the temp sensor and watched it as the engine warmed up, it was all within spec. I’m waiting on my consult cable to get here to be able to look at what the ecu is seeing though.

I capped off the cold start valve, like the one you pictured, just to make sure it wasn’t stuck open letting extra air in, but it made no difference, it’s connected normally now.

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