D40 idling high - SOLVED

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nismo4x4

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Hey guys,

just recently iv noticed when starting the truck up in the morning the revs sit around 1.1 - 1.2 ish then after say 30secs to min it drops to its normal 0.7revish. doesnt matter if aircon is on/off. as soon as i turn it off then back on it idles as per normal but if letting the truck rest for couple hours it sometimes revs high again.

another weird thing is when i turn the car fully off the radio keeps going for about 10secs then turns off

nfi what could be the cause...sounds electrical so i did oldmans ECU reset (neg term removed and ignition on 10secs ect...but stil revs high

any ideas gurus?
 
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Old.Tony

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Idle is supposed to be a little higher when the engine is cold. Let me go out right now and check mine, I haven't started it yet this morning.
 

Old.Tony

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Ok, mine starts idling at around 1,000rpm and after about 5 seconds starts to drop and by 10 seconds it's at 750rpm again.

I would have to wonder if your glows were working properly? I wonder if mine are?
 

nismo4x4

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would make sense to let it idle high for a little bit to get it warmed up however it never use to do it automatically...

also if im in a hurry and turn the truck on and go driving the revs dont reduce within that 30secs to min...as if it needs to sit there idling at above 1 until its "happy" then goes down to 0.7ish revs...like one time after driving for 30mins then stopped at lights...it was still idling high then it dropped to its 0.7ish revs...the motor would def be warmed up after 30mins drive
 
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nismo4x4

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thanks tony...that makes me feel alittle better but i had the truck for 3 yrs now so...it wasnt starting correctly when i bought it?!?!...
 

Old.Tony

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I've had mine for 3.5 years (from new) and I think mine's always acted like that. I wonder if your glow relays are having a little problem? In the box behind the battery.
 

nismo4x4

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hmm what do u suggest? pull them out give them a contact clean? or repalce them...should only be couple dollars if its anything like light relays?!?
 

Old.Tony

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Just remembered the glows are supposed to stay on until the engine is at 80C or so too, so even if you've had it running for a minute - or if you let it cool from normal for about half an hour - the glows should come back on (in case you're testing the relays/fuses).
 

bods

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I don't have a d40, but my d22 is similar on a cold start. Also, when the vehicle is moving (even a little bit, just rolling) the ecu bumps the idle up to about 1000rpm. It does this even in neutral and will stay there until you either speed up or stop, then drop back to normal idle speed.

I guess, depending on how many cold starts you have done since the car was new the glow plugs could be wearing out. You could always pull one out and see how it looks
 

nismo4x4

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interesting...before ignition i wait for the glow dash light disappears then i start it...should look at replacing it aswell
 

bods

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interesting...before ignition i wait for the glow dash light disappears then i start it...should look at replacing it aswell
No, that's normal. It's more of an "idiot light" so people don't just turn the key to start straight away (although you can) waiting for the light just gives them time to get to full temp before you start cranking, supposing everything is in good condition. As soon as you turn the key to on the ecu turns on the relay to heat the plugs, the amount of time the light stays on depends on the coolant temp of the engine. When the light goes off the plugs are still on, as mentioned before the ecu only turns the off when the coolant gets to a certain temp, however, if your morning temps have been lower than usual that may contribute to the higher cold idle.

Another thing to check is your AFM as it may be a bit dirty giving the ecu an incorrect intake air temperature, which will raise idle if it thinks the air coming into the motor is low
 

nismo4x4

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hey Tony i decided to check out the glow relay and replace it but not sure if this is the relay or a fuse...is the yellow an relay?? i was expecting the usual black box looking relays..

i pulled out the entire fuse unit and couldnt see anything i could replace underneath
 

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nismo4x4

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ok guys found the actual glow plug relay and holy shit was it fkd!! so any one with this problem in future.. def check the glow relay as what Tony suggested. Thanks again Tony
 

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Old.Tony

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I won't answer your PM since it's already been answered by yourself :) sorry I have been out for the day. Good job finding it, yeah doesn't look good at all. I don't know if it's a standard kind of automotive relay (with pins 30, 85, 86 and 87) or if it's specialised (which would be the case if Nissan wanted a few more $ from the spares).

Shame that it disintegrated like that. I wonder how much current it was pulling to do that?
 

nismo4x4

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hey Tony nah its not the standard type of relay its a hd 3 pin with some serious spooled coils...googled them and they are about $150-$250... crap!
 

nismo4x4

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bit of bad news...installed the glow plug relay and still it idles high and sometimes continues to rev higher and higher until i turn the ignition off...im worried while im driving and for whatever reason it revs higher and higher until i need to turn the car off...any other ideas? might need to take it to a autoelectrician...
 

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