Rb25 Cold Start Valve Clean

[HR32GTS 4DOOR]

So after having problems starting my car without any throttle ever since the engine swap I decided to do something about it.

Also since I couldn't find a tute on here so decided to document the process.

Disclaimer

Attempt this at your own risk. I am neither an auto electrician nor a mechanic. I take no responsibility for any damage that you do to your vehicle in the process of following this guide.

Difficulty - Easy

Time taken 30-45 min

Things you will need

Flat head pliers

10mm socket with 1/2" drive ratchet and extension

phillips head screwdriver

Carby cleaner

A band aid

Directions

The valve on an RB25 is located under the plenum, on an RB20 is is under the throttle body.

locate the valve it is a metal and black thing with two vacuum hoses attached to each end.

This is what it looks like under the plenum with one of the vacuum hoses disconnected.

Use your pliers to remove the clamp and then gently pull the hose off (where it would be in the above picture). The hoses are old and may be quite brittle so take care in removing them.

Then there are two 10mm bolts holding the valve to the bottom of the plenum, use your ratchet and extension to make it a lot easier to access.

after the bolts are out take off the clamp on the other hose and pull the valve from the hose. Again carefully.

Once you have the valve out it should look like this.

there are four screws holding the black plastic part on. undo these and it should look like this. make sure you dont damage the gasket as this will cause a boost leak if not rectified.

I didn't take the valve appart any further as I didn't think it was necessary.

from here spray both parts with carby cleaner, it will probably be all gummed up with oil like mine was so take your time and it should all come up good.

Final result.

Then just do the opposite to put it all back together, also make sure you do up the four screws nice and tight you don't want to have to pull it back off because its leaking.

[SiR_RB]

Did this fix ur hard start/needed throttle start??

[HR32GTS 4DOOR]

Ah forgot to put that in, Yes it is much better now. still not as good as I would like but improved it a lot. Throttle not needed anymore to start.

[jhjones]

Hey, was your cold start valve plugged in? I've got a RB25 in a R32 that has custom wiring so I'm not sure if there is or isn't a plug for it.

[HR32GTS 4DOOR]

Hey, was your cold start valve plugged in? I've got a RB25 in a R32 that has custom wiring so I'm not sure if there is or isn't a plug for it.

Yeah mine was plugged in. I did the wiring for this engine myself out of an rb20 loom. The plug is a purple/blue plug looks limilar to a side feed injector plug.

[jhjones]

Hey, I found a purple/orange plug underneath the throttle body, so I feed it in between the intake runners and it plugs in to the cold start valve. Will the wiring melt if I leave it like this?

[HR32GTS 4DOOR]

Hey, I found a purple/orange plug underneath the throttle body, so I feed it in between the intake runners and it plugs in to the cold start valve. Will the wiring melt if I leave it like this?

This is how I have mine plugged in, going in between the runners. I haven't had mine melt and I doubt the plenum would get hot enough to do any damage. If it did id say you would have a lot more to worry about.

[Tommmay]

Where abouts under the Plenum is this

I have looked everywhere and cannot find it

Dare say my car does not have one and that is why it is rough as guts on idle

[HR32GTS 4DOOR]

Its under the plenum and above the oil filter. Idle would not really be changed if you didn't have one unless it's just been removed and the vacuum lines were just left there.

[Tommmay]

Its under the plenum and above the oil filter. Idle would not really be changed if you didn't have one unless it's just been removed and the vacuum lines were just left there.

Ahhh its there dont know how i missed it

What i meant by that idle comment is when its cold it needs throttle to start/idle after that it seems to idle good

[HR32GTS 4DOOR]

Ahhk, this is the problem I had. Fixed it by cleaning this. As you can see it had a lot of oil in it.

[Tommmay]

Just done my one and it looked brand new inside lol

could the actual mechanism be faulty?

[HR32GTS 4DOOR]

Just done my one and it looked brand new inside lol

could the actual mechanism be faulty?

It could be, but its pretty simple so it's not all that likely wiring could be stuffed also. when you start your car for the first time does the idle sit a little higher than when warm like at 1500-2000 rpm? or does it just idle at same rpm as when warm?

[Tommmay]

It could be, but its pretty simple so it's not all that likely wiring could be stuffed also. when you start your car for the first time does the idle sit a little higher than when warm like at 1500-2000 rpm? or does it just idle at same rpm as when warm?

Pretty sure it idles at the same rpm and will not start without a squirt or 2 of throttle

Sucks cause there is not much information about this issue

Edited May 22, 2013 by Tommmay

[HR32GTS 4DOOR]

Ok if it idles at the same rpm there is either something wrong with the valve or it isn't being switched by the ecu (more so a wiring problem) unfortunately I don't know how to test the valve to see if it works. Could check if there is continuity between ecu out and the plug for the valve (will have to look up a pin out diagram for the ecu to find which pin) this will tell you if it is a wiring problem or something else. Could also try another valve, I doubt it would be very expensive from a wrecker

[Tommmay]

Ok if it idles at the same rpm there is either something wrong with the valve or it isn't being switched by the ecu (more so a wiring problem) unfortunately I don't know how to test the valve to see if it works. Could check if there is continuity between ecu out and the plug for the valve (will have to look up a pin out diagram for the ecu to find which pin) this will tell you if it is a wiring problem or something else. Could also try another valve, I doubt it would be very expensive from a wrecker

There is continuity in the plug but who knows how it works without a wiring diagram

Ill just take it in the ass rev it every morning lol

[Tommmay]

Put it all back together today and car started perfect

See how long it lasts lol

[HR32GTS 4DOOR]

Haha sweet good to hear man

[Rob_C110GTR]

I've cleaned mine last week and it didn't solve the throttle to start

Should the valve/wheel be fully closed the one where the spring attached to?

[HR32GTS 4DOOR]

I'm not sure but I would assume when you valve is powered (ie when the ecu thinks its cold enough to need it) the valve would be open, so when its appart it would be closed as its not powered. The needing throttle to start can be caused by a few things like vacuum leaks, fuel pump not priming properly etc. If it needs throttle to start when the car is warm then this is not your problem.