Fixing Idle/starting Problems Rb25det & Cleaning Air Regulator Easy Way

[avalanche]

Hi I have an R33 Gtst that has been having an idle problem, where it keeps stalling at low rpm and will not start when engine is cold. After months of trial and error I have fixed both problems without having to take it to Nissan. Below is the Elimination process I did to fix the problems. Hopefully it will work for you. Good luck

Mark

PS; PM me if it worked for you, will be good to know if this was worth writing this up 4 ya’s.

(Many thanks to the people also posted on the DIY section)

>> Proceed working on your car at your own risk. I do not take any responsibly for any damage to your car. If you are not confident enough to do it yourself get someone else to do it. I am only 16 ½ so some things I did in the tutorial may not even be related to the problem but I did it anyway. This is my First tutorial so please feel to correct me if I am wrong and to PM me on questions or tell me if I wasn’t clear enough .<<<

Things you need

Tools

Screwdriver Set

Spanner Set

Pliers

Multigrips

Socket set

New can of Carby Cleaner

New bottle of Wynn’s Injector cleaner

Cotton buds

Things that you may need

Fuel filter

Spark plugs

Air filter

Fuel

Electronic cleaning solvent

Digital mutltimeter

1. Check if your car has a good battery, a clean air filter, good spark plugs and at least a ¼ tank of fuel in it before starting this.

2. Reset the ECU (car computer) by taking off the negative battery cable with a 10mm, pumping the brake 20 or so times then leaving the car sit for 24 hrs. While this is happening you can operate on the car.

3. Change the fuel filter. It is not super hard to do but it can be a bitch. But now after finding out the hot water trick it would have saved me a lot of swearing. It usually has to be done anyway. Valvoline part for fuel filter is VF6 but it says on the box it is interchangeable with Z200. Here is a tutorial

http://www.skylinesaustralia.com/forums/in...;hl=fuel+filter

PIC 1 fuel filter

4. Clean IAC (Idle air control valve) valve. The Iac valve is usually a cause of bad idle. Really good tutorial here

http://www.skylinesaustralia.com/forums/in...howtopic=110431

I found though on my ECU there was no idle screw. Only the one on the acc. Also not to disconnect the TPS (Throttle positioning sensor), Instead the Brown aac plug (pic 2) before mucking with the idle screw (pic 3). To get a better result from cleaning the air regulator, spray a fair bit of carby cleaner down the pipe once you have it off. This pipe is the one that goes straight down from the iac valve assembly to the air regulator( PIC Z). More info on part 8.

PIC 2 Iacv assembly

PIC 3 Idle Screw

PIC Z Pipe goes down to air regulator

5 Clean the AFM ( air flow meter). The air flow meter is located just after the air filter and has a grey plug going into it (PIC 4) . Disconnect the Grey plug, take out the 4 bolts that hold it in, watch you don’t lose the big o –ring seal (between the AFM and the air filter) and lift up and twist it. It should come out easily. My one was really dirty. Spray both ends of the middle sensor thing and around with electronic cleaning solvent or carby cleaner then wipe out with a rag. Avoid flooding the box it is joined to with carby cleaner, unless you are using the solvent then it should be ok. Avoid touching the sensors with the rag and instead use cotton buds to clean the sensors. Do not attempt the unscrew the 4 screws that are on the side of the afm plug! The prongs are connected internally to the sensors. I learnt this the hard way and had to re-solder it. This is probably not necessary but if you have one, use a multimeter to check the circuit from the sensor inside to the prong that is exiting on the plug. There should be a circuit on all of them. Before putting it back in it would be a good idea to spray a little carby cleaner in the duct to the turbo and wipe the muck out it there is any. Reverse this process to get it all back it and remember the black o-ring.

PIC 4 AFM

6 Clean the butterfly or throttle valve. Over time muck can get onto the tips of the butterfly and surrounding causing a sticky accelerator this was the case on mine. Take out the 2 bolts that hold the piping before the butterfly (PIC 5). Use a ratchet and undo the pipe clamp just before the butterfly (PIC 6). Pull the clamp back and pull off the rubber pipe and the piping. Spray all over the butterfly and return spring with carby cleaner. Push the throttle open and spray in and around the butterfly. Go in the car and pump the accelerator a few times and spray again. Wipe away as much black muck as u you can. Then reverse the process to get it back together.

PIC 5 Two bolts holding the piping on

PIC 6 butterfly piping clamp

7 If you have an aftermarket BOV (blow off valve) with an adjustable spring, crank it in to the max but do not over tighten or you will ruin the thread. If you do not have an adjustable, the same thing can be achieved by pulling out the tube that goes to the bov and blocking it with a rivet. Ok this is my theory probably not true but to my knowledge people have been having a lot of idle problems with aftermarket BOVs. I think when at low rpm the bov opens and allows air to seep into the intake. So by cranking it up it seals the bov better ands stops leaking. This is only a theory of mine and is probably not true. But I tried it and it did have some impact on my idle. Just remember to return everything back to normal once you have fixed your problem. (PIC 7)

PIC 7 BOV

8 Clean the air regulator the easy way. The air regulator is usually a cause of high idle. Cause of mine. Over time the regulator may get stuck and seizes at a point making it hard to set idle right and start. There is a tutorial on cleaning the air regulatorhere but it is for a different motor and it is a lot harder to do on a rb25.

http://www.skylinesaustralia.com/forums/in...l=air+regulator

The air regulator on rb25 is under the plenum or throttle body but above the oil filter and has a 2cm diameter black pipe going in and a 2 cm black pipe going out (PIC 8). If you follow where the black pipes come from the one going in comes from the Iac and the one out comes from it goes to the bottom of the plenum (PIC 9). It would help if you have already sprayed carby cleaner down the Iac pipe like I said in part 4. Since it is nearly impossible to get it out of the car I did this. The pipe that goes down from the plenum into the air regulator in pic 9 , I got the clamp and the pipe it off with a pair of multi grips. Then sprayed lots or carby cleaner down it and let it sit for a minute. Then I attempted to re connect it. It is really a bitch to get back on, but in the end I got a friend of mine to keep in place from the passenger side with a long screwed driver while I pushed it back up from the driver’s side from under the plenum. Then put the clamp back in place.

Now if you have a bov with a little filter take it off now (PIC 10). There is a pipe coming off the main piping before the butterfly and the bov (PIC 11). This pipe I think bypasses a closed throttle to get air for idle. Undo the clamp and remove the pipe. Block the line that the filter was on before with your fingers or something. Now spray a heap of carby cleaner down the pipe and take a deep breath and blow into the pipe. Avoid giving yourself a stroke or a headache. You should be able to hear the air being pushed into the throttle body. Repeat this a few times with a few breaks so you don’t overload your lungs. Try opening the butterfly while u do it, it will get easier. You also should feel if you have strong lungs that there's a point where you can’t push any more air into the pipe until it has passed though. I think this means the regulator is working. If not you may have a blockage or your air regulator is really ceased up. Try this a few times then rejoin the pipe and put the filter back. Have a cuppa!

PIC 8 air regulator ( hard to see) arrow goes back to iac valve

PIC 9 pipe that goes into the plentum from air regulator ( hard to see and get to.)

PIC 10 BOV Filter

PIC 11 Air Bypass pipe for idle

9 Now these are probably also not necessary but clean these heat sensors. They are located on the hose off the radator, left if you are looking at the engine bay (PIC 12). I'm not quite sure what the are for but I did it any way. Un plug them, take them out, big one is a 19mm and the little one is a 12mm and wipe them clean. Mine had like mud all over them. Then put them back in.

PIC 12 heat sensors

Clean the PCV valve (positive crank ventilation valve) (PIC 13) this little thing has something to do with re using unburned fuel or some shit I don’t really know. Just pull it out of the cam cover and shake it up and down. If you hear no ticking sound take it off the pipe and flush with carby cleaner. Then put it back in.

PIC 13 PCV valve

Clean the O2 sensor (oxygen sensor) (PIC 14). It should be right after the turbo taped into the exhaust undo and un plug it and take it out blast it with carby cleaner. Then put it back in.

PIC 14 O2 sensor

10 Check for vacuum leaks. Vacuum leaks can affect your idle big time. Look around at all the black pipes and tubing for cuts, holes and if you can check if they are blocked up. I had a line that was blocked up by the previous owner that was not done properly. It was sucking air. (PIC 15)

PIC 15 Shitty Plug

11 After u think the ECU has been reset reconnect the battery but do not turn the ignition on yet. Next to the battery is a fuze box. The blue fuze 4th one in is the fuel pump (PIC 16). Pull it out. We are trying to get the motor to starve for fuel. Now turn the ignition on and wait 5 seconds. You will not hear the fuel pump. Then try to wind over. Try full accelerator no accelerator. If your car starts then dies like mine don’t worry. Keep winding for a few more cranks after it dies. Your car may not start at all just wind it for 10 seconds. Turn the ignition off, put the fuze back in, turn the ignition on until the fuel pump stops then try to start. 1st try no accelerator, then accelerator if I didn’t start. What happened?

PIC 16 fuzes

12 If its going go for a short easy low speed drive and get it up to normal temperature (about half way on the gauge). Get in neutral with hand break on you will need an 8mm and a screwdriver. Screw out the throttle stop so it doesn’t touch, then screw in until it just touches (Pic 17). With no ac or heaters on, disconnect the brown plug on the acc, wind the idle in for less or out for more to some were between 850 and 1000 rpm then reconnect the plug. Is there a change in your idle when you reconnect the plug? If so there may still be the air regulator because before I flushed it the idle when I reconnected it would go up 200 rpm from where it was disconnected. But now there is no change.

PIC 17 throttle stop screw

13 Listen for vacuum leaks. You will be able to hear them. If you need to, pull a random one out just so you know what you are listening for.

14 Run some injector cleaner in your fuel tank i've been told that Wynn’s brand is the best for you’re money. Don’t use the other 50ml ones, its like pissing in the ocean, it will not do anything.

Hope this has helped you. If not well at least you’ve tried to fix it before you take it to your Nissan dealer and spend a lot more.

[paulr33]

damn good artiicle, well done, thanks

[fob2nv]

Awsome dude.

[Flash89]

what about a RB20, will it be similar??

[avalanche]

um im not quite sure but it should be close to the rb25 just things may be in different places.

[TurboDoseBro]

This is a very nice tutorial, but i wouldn't recommend using carby cleaner on electricals.

[mr-blue32]

I HAVE A s2 RB25DET in my R32 and at warm up idle speed there is a tiny miss in it but once its warm and the water temp is at about 8o+ degrees or higher the idle seems to chase itself and fluctuate between the recommended 650rpm and about 1000 rpm would doing any of this fix those issues or would it be something else? im new to owning a skyline so any help would be much appreciated

p.s the motor is only about 68,000kms old and was only driven 7000k's in 8 years and smells a little rich at times so could it possibly be the tune has gone out from it sitting in a shed for so long before being sold to me

[my94coupe]

Hey, Any chance the OP could reinsert the photos for this post?

I am still chasing issues with mine and looking for all the assistance i can get.

Thanks

Cheers