Cheaper Alternative To Rb25 Aac Valve

[Ty1]

hey guys just recently my aac valve started playing up. I tried taking it apart and cleaning it but no matter what i tried I couldnt get the idle below 1000rpm. I even tried hooking my car up to nissan consult, setting the base timing and disconnecting the tps but i couldnt get it to idle any lower. Instead of getting a second hand aac valve I wanted a brand new one and there was no way I was paying over $600 from nissan. I ended up jumping on ebay and typing in 'nissan aac valve' to see if there were any that resembled the rb25 valve. turns out the sr20 s14 aac valve is completely identical in almost every way and only $250 including shipping from the states. I've attached pictures of the r33 and s14 side by side. The only thing I had to do was take the 2 little screws out of the big gold looking solenoid and rotate it so the brown plug is facing up instead of down. I also had to remove the t piece junction for the vaccum hoses from the r33 one and fit that to the s14 one as it had a welsh plug blocking the hole. hooked it all up yesterday and works perfectly i can actually adjust my idle lower now. also purchased a genuine rb25 aac valve gasket and fit to the s14 valve with no dramas. Hopefully this may help a few people out there

[discopotato03]

Thread resurrection .

Been searching for hours about R33 RB25DET IAC valve/housing assemblies because I reckon mines shot . I went to a self serve wrecker yesterday to see if I could find anything similar in a locally available Nissan .

Turns out that N14 Pulsar GA16DE cars use the same gasket and pattern as R33 RB25DET , the 1993 ones anyway . N15 GA16DEs use a totally different system .

An early 93 N14 had the older IAC motor with the sleeve valve system like I think R32 RB20s had . I got the complete assembly off an 11/93 N14 and from the outside it looked the same as my 96 GTS25Ts one . Where OP found a blanking plug the N14 unit has a tube the same size as the RB25s one but without the cross tube that's plumbed back to the crossover pipe . If you could swap the pipes over the N14 one would probably work fine . I grabbed the solenoid itself to try but it does pretty much the same thing as the original one does , I think the valve or the housing bore wears and leaks and this gives an erratic idle and undershoot returns at times . For the record I've tried every which way to tune around this and nothing works . I have to use an idle "retard ramp" to hold the idle speed back and still get issues . My idle screw is almost all the way in . Clearly it has a leaky valve issue .

Kudos in QLD can bring this IACV assembly in but they are exy like 500 odd dollars .

Can someone tell me how to get the steel tube out of the housing without destroying it plz .

Thanks in advance cheers A .

    

[discopotato03]

Just on this I found a picture on an American site where someone stripped an IAC housing ie removed the epoxy resin over the plunger/pistons brass plug and pulled the guts out . He said once the resin is removed to screw the brass plug in first to get the resin out of its fine threads . Clear and then screw the plug out and rempve the piston and spring . There is a youtube of someone trying to stretch the spring to increase the preload on the piston .

 

More later cheers A . 

[admS15]

Just on this I found a picture on an American site where someone stripped an IAC housing ie removed the epoxy resin over the plunger/pistons brass plug and pulled the guts out . He said once the resin is removed to screw the brass plug in first to get the resin out of its fine threads . Clear and then screw the plug out and rempve the piston and spring . There is a youtube of someone trying to stretch the spring to increase the preload on the piston .
 
More later cheers A . 

I tried that and failed miserably. Ended up wrecking the valve. I could adjust the valve manually still but the ECU had no control over it. Funnily my car idled fantastic with the valve in that state, could even idle smoothly at 600 rpm, just wouldn't increase revs for AC and cold start. It was summer time so cold starts where still ok. Not sure how it would go in winter. I ended up replacing it with a 2nd hand valve and idle quality went back to being slightly erratic. I believe you are right and these valves can play a massive part in idle quality.

[discopotato03]

Yes the N14 Pulsar GA16DE one I "looked at" in the you pull it wreckers will never work again , I don't experiment with my original import car parts if I can help it .

I suspect some of the probs with these things is that the plunger valves spring loses tension over time and no amount of cleaning or changing electrics can fix this problem .

I think they are fitted together and the spring tension is pre set with that brass bung and then its epoxied so it won't screw itself in or out . If I can find a way to successfully remove the epoxy and get that bung out without damaging it or the alloy castings threads I can possibly adjust the spring tension . I really need to see one apart to see how the valve seats and seals . I can't justify 500 dollars for this so I'm looking for a more sensibly priced fix .

Also what I REALLY want to know is how hard is it to pull the main vacuum tube out and swap it into another IAC assembly . The ones that are similar enough are the S14 SR20DET ones and the late 93 N14 GA16DE ones . The main difference is the steel tubular part .

A .

[-S-]

When i tried adjusting mine, it just wouldn't drop or increase the Idle rpm... good info. Didn't know the aac valve will get f**ked overtime... Will have a look into sourcing a second hand unit ...

[Girorostar]

On 6/17/2017 at 1:54 AM, discopotato03 said:

Also what I REALLY want to know is how hard is it to pull the main vacuum tube out and swap it into another IAC assembly . The ones that are similar enough are the S14 SR20DET ones and the late 93 N14 GA16DE ones . The main difference is the steel tubular part .

A .

Hi everyone. I'm also very interested in knowing this. 

[Missileman]

I've had my rb20 valve completely apart, used a dremel to remove the resin and a right angle scribe to get the last of it out of the threads. If you need more preload, then screw the brass plug in a touch more, I didn't have to stretch the spring

[Ty1]

Nice thread revival [emoji3] 5 years later and still going strong. One thing i forgot is with the r33 't' piece, i had to slightly enlarge it for it to fit snug into the s14 valve

[discopotato03]

Thanks for that but again , how did you get the T piece out without damaging it .

I'm off to a U Pull it wrecker now to try and get one off a 93 Pulsar GA16DE , they are same thing but with a straight tube out of the IAC body .

[discopotato03]

I just found these . 

http://www.skylineowners.com/forum/21-tuning-technical-questions/135514-aac-valve.html

And this .

http://www.southernskylines.com/howto/r33/aacv_aac.html

Obviously its a common problem but not too many people talk about it . Lots of agro for and time weakened spring .

A .

Edited June 30, 2017 by discopotato03

[Ty1]

Thanks for that but again , how did you get the T piece out without damaging it .
I'm off to a U Pull it wrecker now to try and get one off a 93 Pulsar GA16DE , they are same thing but with a straight tube out of the IAC body .

From memory It literally just twisted straight out quite easily

[discopotato03]

Ok .

I retrieved the N14 IAC housing I beat up trying to get the brass bung out . Its now gutted and cleaned up at home .

I can sort of see why these assemblies are expensive but the Australia Tax makes them stupid expensive .

Anyway there was a fair amount of machining and threads in the alloy casting and they have a stepped brass bush pressed into them . I think the problems are mainly the spring relaxing and not allowing the tapered section of the sliding pin valve to move back into its bore hole . It doesn't actually seat against the shoulder unless the solenoid gadget is removed . The parallel section is a neat enough fit in the brass bore not to pass air until the tapered section is exposed , if the spring tension is weak the sliding pin obviously isn't pre loaded enough . It's supposed to have spring loading from both sides ie the spring on the brass bung side and another in the electric solenoid side . Obviously if the one on the bung side is weak then the one in the solenoid side wins and the sliding pin is biased away meaning closer or at the point of exposing the start of the taper . I just wish Nissan hade made a way to have the bung adjustable ie longer and fixed with a lock nut .

Long short I think the best fix is to remove the epoxy/bung/spring/sliding pin valve and clean everything properly . Then refit and adjust the spring tension till it works properly . Then remove and use a tiny dab of thread lock to stop the bung screwing itself in or out .

[discopotato03]

Got stuck in last Saturday but something to approach with caution .

Removed the R33 RB25 IAC assembly and gutted it of all internals . The biggest surprise was that the epoxy gunge in my unit went right through to the outer spring base - in other words no brass plug . Luckily I had the Pulsar one because Nissan had the female thread for it to screw into . Had to buy a thread file to clean everything up enough to work . Its all back in now with a dab of silicon on the outside of the plug to stop it turning . The internals are slightly different on the Pulsars shuttle valve ie smaller diameter valve and guide . With the steel tube junction just place that in a vice with soft jaws and turn the casting to sort of twist it out . Went back in fairly easily .

Sadly none of this fixed my idle problem but it could work for others .

I noticed my engine making a distinct sucking noise through the PCV valve and pinched it shut , idle speed drops . ATM I have an old brake hose clamp keeping it shut and adjust idle speed to suit . It is now better  , but not perfect , though the ViPec software shows lower manifold pressure at idle and over run and throttle response is much better at low revs .

A .

Nearly forgot , the tool you need to fit the narrow concave slot in the brass plug is called a "Dzus" tool or screwdriver . These look like a very wide thin plain blade screwdriver but the blade is slightly convex rather than straight . They are intended for some aircraft and motorsports fasteners .  

 

[admS15]

Got stuck in last Saturday but something to approach with caution .
Removed the R33 RB25 IAC assembly and gutted it of all internals . The biggest surprise was that the epoxy gunge in my unit went right through to the outer spring base - in other words no brass plug . Luckily I had the Pulsar one because Nissan had the female thread for it to screw into . Had to buy a thread file to clean everything up enough to work . Its all back in now with a dab of silicon on the outside of the plug to stop it turning . The internals are slightly different on the Pulsars shuttle valve ie smaller diameter valve and guide . With the steel tube junction just place that in a vice with soft jaws and turn the casting to sort of twist it out . Went back in fairly easily .
Sadly none of this fixed my idle problem but it could work for others .
I noticed my engine making a distinct sucking noise through the PCV valve and pinched it shut , idle speed drops . ATM I have an old brake hose clamp keeping it shut and adjust idle speed to suit . It is now better  , but not perfect , though the ViPec software shows lower manifold pressure at idle and over run and throttle response is much better at low revs .
A .
Nearly forgot , the tool you need to fit the narrow concave slot in the brass plug is called a "Dzus" tool or screwdriver . These look like a very wide thin plain blade screwdriver but the blade is slightly convex rather than straight . They are intended for some aircraft and motorsports fasteners .  
 

Same thing I found in my r33 valve. No brass plug. I ended up damaging mine in a way that made the spring and diaphragm at the bottom permanently shut. Car idled beautifully with it like that but idle up for a/c and cold start was no longer working.

[discopotato03]

Thanks , that sort of confirms that Nissan cheaped out with the R33 RB25 IAC assembly so don't attempt to pull one apart if you don't have that brass plug .

I'm not sure how but I think my engine must have an air leak into the crank case or cam covers because it wants to pull so much air through the PCV valve at idle . It does have the hose from the exhaust side cam cover to the turbos air inlet with a brass reducer with an approx. 5mm hole in it . My engine doesn't like how much air it can drag through when as the factory had it though Nissan used MAF sensing rather than MAP .

A .

[discopotato03]

To add a bit more . I discovered the de-epoxied brass bung makes for a slight vacuum leak to the inlet plenum . I'd say the epoxy on the IAC units with the bung isn't just there to allow factory pre-setting (on the early ones) and prevent tampering . If it was designed to be adjustable it would have a seal something like the idle adjustment screw has .

 I got a small bottle of Loctite aircraft gasket sealant which never sets hard , I think a smear of this on the threads should minimize the leak and stop the bung moving with vibration . 

A .

[Missileman]

...me I just used 5 min epoxy with a bit of talc/q-cel added to thicken it up.

[discopotato03]

Found out a bit more today .

Found another 2 Pulsar N14 IACs and when the epoxy was removed one had a cream coloured plastic bung and the other the brass one .

Also got to play with a 97 U12 KA24 one and it was plastic too . I suspect the R33 ones are plastic and if you attack them through the epoxy they break up , the give away is the base with the hollow boss that locates the spring and the end of the hollow shuttle valve . 

Also the springs are different rates in these IACs , found soft medium and firm ones so far .

A . 

 

 

[discopotato03]

Update , bought a couple of late S15 IAC valves cheaply and fitted the cleaner one with the R33s T piece . Also had to turn the IAC solenoid around so its socket faces upwards like R33 . Downside to late S15 IAC assembly is a return to a plastic idle speed screw which doesn't interchange with the earlier brass ones .

It does work a bit better but I'm beginning to think part of the issue is computer settings ie letting the valve park itself slightly open at low revs . Some computers want to hold the valve shut until the engines virtually at idle speed resulting in an undershoot at return to idle .

Just on idle speed screws . Many of these get hacked up and I thinks its because people use Phillips head screwdrivers on them . Phillips is a bastard of a system because it was a production system designed to cam the driver out if overloaded , this also butchers the screw head .

Before the Phillips system came out the Japanese developed a cross head type driver and called it JIS for Japanese Industry Standard . At a glance JIC screwdrivers look like Phillips but the taper on the point is less and they don't bottom out as easily . Bottom line is they fit and grip better and do less damage to the screw heads .

Real Japanese JIC screws have a dot next to the cross and Phillips screwdrivers kill them . JIC screwdrivers fit both screw heads and in my experience work better on Phillips screws . 

Vessel make JIC screwdriver sets and they work well .

A .