Rb20det Sometimes Won't Idle

[Samuel Leonard]

Every morning when i start my car (or when it's sat for long enough to get pretty cold) my engine won't idle properly.

When i start it it idles fine. but if it ran for a few minutes and then i gave it a rev to 3000 and then took my foot straight off the accelerator, the revs would drop and then die right down to maybe, half my idle speed or less.

i have to give it a bit of throttle to keep it running.

once the car is warm it's absolutely fine.

it also won't start when cold without a bit of throttle. is this normal for a fuel injected engine?

i can film it if anyone wants to see what i mean.

Edited May 13, 2010 by Samuel Leonard

[PUDZ 32R]

try unplugging your ECU water temp feed. on the top rad hose. if it runs fine just really rich maybe your temp sensor is dodgy.

or it could be a problem with your AAC valve but that is unlikely as it doesnt do it when its hot.

[Samuel Leonard]

try unplugging your ECU water temp feed. on the top rad hose. if it runs fine just really rich maybe your temp sensor is dodgy.

or it could be a problem with your AAC valve but that is unlikely as it doesnt do it when its hot.

Ok, my ECU is just left of the passengers feet, right? How will I know which to unplug? Sorry. Is it labelled? Or do I need to look it up?

Edit: ok, just realised you said on my top radiator hose thanks I'll try it now would this be why it needs me to tap the acceleratora bit to start too?

Edited May 13, 2010 by Samuel Leonard

[Samuel Leonard]

try unplugging your ECU water temp feed. on the top rad hose. if it runs fine just really rich maybe your temp sensor is dodgy.

or it could be a problem with your AAC valve but that is unlikely as it doesnt do it when its hot.

There are two plug. On this hose just before it goes into the block. Which one or both should I unplug?

[Samuel Leonard]

There are two plug. On this hose just before it goes into the block. Which one or both should I unplug?

lol. that made no sence typed that from my iphone and i was rushing

i had seen a temp gauge plug before on a kawasaki motorbike so i worked out which one.

un plugged it and it stopped the problem!

thank you so much! what does this mean? i need to get the actual thermometer replaced? or the ECU is doing something odd with the temp info?

[tiberis]

when you disconnect the temp sensor, the ecu should default to a look up table and say "i will assume the engine is cold for a while, then after a few mins it should be hot already' rather than look at the signal.

what must be happening in your car is the sensor is broken, sending the signal to the ecu that the engine is hot all the time, hence it doesn't apply the cold start stuff it needs to.

i would make sure the connector is clean of corrosion and is making a good contact first, reconnect it and see if it helps. if it doesn't then you need a new sensor, i can't imagine they would be expensive. very easy to switch out, just unscrew the old one and screw in the new one. just watch for the coolant that will leak out also DO NOT do this while the system is hot/ pressurised or bad stuff will happen (ie, getting burnt).

[Malteaz]

"There are two plug. On this hose just before it goes into the block. Which one or both should I unplug?"

WHich one did you unplug?

[Samuel Leonard]

"There are two plug. On this hose just before it goes into the block. Which one or both should I unplug?"

WHich one did you unplug?

i remembered that the temp only has a positive. it uses something elses as a negative so i unplugged the small plug with only 1 pin into the plug.

[Samuel Leonard]

when you disconnect the temp sensor, the ecu should default to a look up table and say "i will assume the engine is cold for a while, then after a few mins it should be hot already' rather than look at the signal.

what must be happening in your car is the sensor is broken, sending the signal to the ecu that the engine is hot all the time, hence it doesn't apply the cold start stuff it needs to.

i would make sure the connector is clean of corrosion and is making a good contact first, reconnect it and see if it helps. if it doesn't then you need a new sensor, i can't imagine they would be expensive. very easy to switch out, just unscrew the old one and screw in the new one. just watch for the coolant that will leak out also DO NOT do this while the system is hot/ pressurised or bad stuff will happen (ie, getting burnt).

ok. thanks. i just can't work out why my temp gauge still works with the dud sensor? you'd think the gauge would be getting the same reading, right?that's why i thought it could be a problem with my ECU but i'll just buy a new sensor for now. thanks for your help.

[tiberis]

usually there are 2 temp sensors. one for the gauge one for the ECU.

the gauge one is supposed to be a cheaper less accurate one where as the ECU sensor is supposed to be more accurate because it's more important. this is also reflected by the fact that the temp gauge will normally always rise to the same point regardless of fluctuations in engine temp.

either way, new sensor should be all you need, i've not really heard of ECU's half dying like that anyways.

[Samuel Leonard]

usually there are 2 temp sensors. one for the gauge one for the ECU.

the gauge one is supposed to be a cheaper less accurate one where as the ECU sensor is supposed to be more accurate because it's more important. this is also reflected by the fact that the temp gauge will normally always rise to the same point regardless of fluctuations in engine temp.

either way, new sensor should be all you need, i've not really heard of ECU's half dying like that anyways.

oh no... so you mean i've bought a new gauge one? haha. i'll ask the guy if i can buy the other one too...

[Samuel Leonard]

i need a new ecu temp sensor. does anyone know where to get one in adelaide? any wreckers to try or anyone wrecking a whole gtst?

i would love to get this sorted out! it must have been weird coincidence that the engine nearly stalled with the guage one plugged in then stopped when i unplugged it? it nearly stalled with that guage sensor unplugged this morning. spewing because i just bought a new one thinking that was the problem... ah well. you win some you lose some. i'll try unplugging the other one tomorrow morning...

[PUDZ 32R]

it sounds like a fluke that unplugging your guage temp sensor "fixed" your problem as the guage sensor has nothing to do with the ECU. the ECU sensor has 2 wires as it cannot earth or the ECU will not get a feed. why dont you go to nissan and order a new one instead of looking around for a cheap second hand one that may even still be dodgy?

[Samuel Leonard]

it sounds like a fluke that unplugging your guage temp sensor "fixed" your problem as the guage sensor has nothing to do with the ECU. the ECU sensor has 2 wires as it cannot earth or the ECU will not get a feed. why dont you go to nissan and order a new one instead of looking around for a cheap second hand one that may even still be dodgy?

yeah, it was a fluke. someone has offered me a 2 pin sensor off of an rb20 that's sitting in their shed. would you still think not? he's offering $30 posted and i could buy a brand new one for $89 so i think i'll buy the $30 one. hopefully it works

[tiberis]

From what i know/ have experienced (not that it counts for much ) the sensors don't die that often, so i would hope that the one from the RB20 would be fine.

One thing i do strongly suggest though, is before you fit it in, make sure the contacts/ pins are clean and don't have any corrosion on them. that little bit of corrosion can create enough resistance such that you get a reading way off from what it really is.