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Hey guys. I've got a rough idle issue on my R34 GTT RB30/25DET Neo. I've worked on my RB for years and this is the first time where I don't have a fkin clue why it's happening, its baffiling me. Here's a video of it in action: Long story short: My daily R34 decided to randomly start doing this weird RPM idle fluctuation thing and it wants to die on me sometimes and I've got a higher than normal pressure in my fuel line before the fuel rail which I'm thinking can be contributing to this issue. The long story: This is my daily and the car has always performed really well for me up n till now. It was tuned on haltech platinum pro (running on board map sensor) 4 months ago and did 440hp (on 98ron) and has been driving really well, no issues what so ever. Then one day (about a month ago) I came home from work, fuelled up, popped into the shops and then came back, got in the car to head home, started it and it started idling really rough. Like, I would start it and then it would instantly die on me. So I had to rev it to keep the engine alive and I had to baby it home. And it would also do this weird RPM fluctuations where the rpm needle on the cluster goes up fast then down fast like its glitching weirdly (can see on the video). Note: nothing has been changed on the engine since the tune nor has the ecu been plugged into anything since the tune. So this problem has occurred randomly and is still the same today. Also to note: this happened when the car was at full operating temp (was probably a 30 degree day). And the same idle issue will happen on cold starts. I've attached my complete list of mods here. I haven't been driving the car since. So I've plugged the haltech ecu into my laptop to check for any error codes, nothing. I let the engine idle and I watched the sensors on the haltech ecu manager, nothing odd, and no errors. Temps all look good. TPS voltage is good. I've got the haltech hooked up to a wide-band O2 sensor (pro sport gauge kit) and the afr starts off rich on cold start then eventually it goes to 14.2 like normal, so afr seems fine and normal to me. Since I've changed the spark plugs, it now won't die instanly on me but it still idles weirdly. The weird thing is, the RPM on my cluster fluctuates up and down but the RPM on the haltech shows normal-ish (no fluctuations). Note: the video was taken after I have done all the checks below. So here's the list of things that I've checked off and done on my list to try and eliminate possible causes: • Compression test: perfectly fine like it was before the tune (phew!😅). • Changed spark plugs to new ones: this helped a bit with the rough idle, old plugs were all black (they were about 3000kms old). • Did the old quick coil plug test by un-pluging one by one while engine is idling to hear for changes in rpm: rpm/idle changed as they should on each one. • Changed fuel filter: still the same. • Checked TPS sensor on haltech and it reads correcly. 0.45v no throttle and 4v WOT. • Cleaned IACV with a new gasket: nothing changed. • Swapped the IACV with another known working one: nothing changed. • Swapped CAS to a known working one. Nothing changed. • Unplugged the water temp sensor: I know it’s not this because when I unplug it, it would show some weird temp on the haltech software and when i plug it in it shows normal. • I've tried attaching the R35 PRP coil plug harness's ground cable to somewhere els on the head: nothing changed • I've tried putting a jumper lead on the negative battery terminal and then attaching it to the head and block to see if its a grounding issue: nothing changed. • I've checked the timing marks on the cams and crank all line up. • Changed the fuel pump horn relay (constant 12v mod) to a new one: nothing changed. • I've taken my haltech ecu out and then tested it into my brother's r34 with his map to check if the ecu is still fine, and it is. Now here's where it gets a bit interesting (and let me know if it's irrelevant); I checked the fuel pressure for the first time ever by tee'ing in a pressure gauge between the fuel filter and damper that enters into the fuel rail (can see on the video). When I prime the fuel pump, it goes to 43ish psi, which it should be according to the R34 workshop manual. Then when I go to start and idle the engine, it stays on 50psi. The workshop manual says that it should be about 32psi. So I immediately thought its my fuel pressure regulator and I changed it to a known working one. And still... it's idling at 50psi fuel pressure. When I take off the vac line on the FPR, nothing really changes. So then I changed the fuel damper that sits on the fuel rail to a known working one: still the same 50psi. Then I hooked up a long hose onto the exit of the fuel rail straight to the fuel tank flap to see if there are any blockages: it dropped a little bit by 2psi... So no real restriction in the return line. So now Im wondering, if there might be a blockage in the fuel rail or my 640cc xspurt injectors are maybe blocked? 🤷‍♂️ The question I have is; is this fuel pressure on idle (50psi) normal for an RB that has a Walbro 225 fuel pump with the constant 12v mod, with upgraded injectors + standalone ecu on a stock fuel rail and stock fpr? And would this high pressure be my main culprit for my shithouse of an idle? The other interesting thing I found/tested, was; i swapped out the cluster to my old stock nissan one to see if the RPM fluctuation thing also appears on that one, and it did the same thing weird RPM fluctuation on my old nissan cluster. So something weird electrically is going on that is contributing to this idle issue (maybe?). The fuel pressure also doesn’t seem normal, so I wanted to check in with you guys before i go pulling the fuel rail off (which is such a bitch to do!). What do you guys think this might be? Can I test some other stuff? Does the haltech platinum pro ecu have a diagnosing feature of electrical components that I can try? It can't be the tune/map because it ran perfectly fine for 3 months after the tune and no one has touched the map since. The next thing I’m tempted to try is injector cleaner which I've never tried before. Can I pour it straight into the feeding fuel line instead of in the tank? Can injector cleaners damage stuff when not diluted in the tank? mod list.txt

Hello, this is definitely my favorite forum. I always manage to resolve my issues when I come here! However, I’m dealing with a problem I’m not sure how to address. I’m hoping to receive pointers or guide on my quest to solve this issue. Issue: On cold start, my swapped 180sx with an rb25det will crank and idle normally, but as soon as it starts warming up. There’s a subtle backfire, little pops if you will. At operating temperature, the idle begins to fluctuate up and down between 800-1200RPM. Eventually, only when fluctuating RPM it will drip my 150A breaker at the battery and the g4+ ecu will lose power and shut off. Or the ECU will shut off without dripping the 150A breaker and everything else stays on: radio, fuel pump, gauges, etc. Questions: 1. What may cause the ECU to turn off? 2. How to I measure voltage to the ECU? 3. Is it possible there is a short causing the current surge to drip the breaker and make the ecu behave erratic? 4. Anything I should check? Parts installed before problem began: • GTR R35 Coilpacks • Bosh donut knock sensors • PRP trigger kit • 270A alternator • LINK G4+ lambda CAN wideband sensor I did drive the car with all parts installed with one issue. The ECU had a wideband sensor overheated code, which I resolved by addding a 200uF 12V capacitor. Other than that, I didn’t deal with issues until this. Any help is greatly appreciated. Thanks!

Ok. So I've made another post about my car not idling properly, being generally rough and having hesitation when accelerating. Now, if you've seen my other post, you'll know that I've changed my spark plugs, put some spitfire coils in, cleaned the AFM and everything was running fine still. The car still ran and was drivable. Now, only since I took off the TPS and tried cleaning it, the car is no longer drivable. No freaking clue why my tps would do this, but now when I press the accelerator, the car almost dies. It's responding to the tps changing resistance, but it's as though it's being flooded with air or something. But when I press it, the idle doesn't go back up, it stays at that certain rpm range. The video of what I'm trying to explain is at the top. Really need some help as I need my car to at least be drivable for tomorrow. Cheers.

Most likely one of the thousands of posts about idle problems with an RB engine. So, my r34 has been running like a dream. I've owned it for about 4 months, and never had a single problem. Put in a boost controller myself about 2 months ago, never had a problem. In the last week, my car has decided to drop to 500RPM when warm, and at a complete stop, and in the last day, it's done the same thing, but the idle was very rough and a bit up and down. Here's a video of my car idling, ignore the engine as for some reason on camera it comes out to be extremely loud, but IRL is a lot quieter for some reason. I just wanted you to focus on the exhaust pattern, as that's what I'm referring to when I say rough idle. This morning when I cold started it, it did the rough idle thing, dropped to 500RPM, and went rough, rough rough and then stalled for the first time ever, started it up 2 seconds later and was all good, started fine no worries. I took of the cam cover to check the timing belt, but it looks like it's in very good condition. No tears or anything. Here's the video: R34 idle Problems I'm in need of some feedback if possible, just some recommendations on what I should look to fix, maybe if someone has experience the same problem I'm having. Cheers heaps guys!

Hello, Ive just completed my Rb25det neo swap into my r32. Its having a miss on idle, I get RB's dont idle great anyway but i just wanted to get an idea on what might be causing it. Below vid sounds a bit like my car (but isnt my car) My engine is fully stock, just front mount and a walbro fuel pump. I have a cheap FPR I'll chuck in to make sure its not getting too much fuel. I have only done one pull since the swap and it felt ok, I just wanted to make sure it was safe before I take it for a proper drive. Cheers

I've had idle issues and noticed that the fuel trims max out (ST +25%, LT+10%) at idle, but look normal at other times. My guess is that i've caused an air leak when I installed Scottys cooling mod, which requires the manifold removal. I did pull the injectors out, so there could be a leak in a bottom seal or two, and i reused the gaskets (which all looked good). Do you guys re-use the gaskets? Anyone know the bottom oring part numbers or the dimensions so i can get non-genuine ones?

I Have an R34 GT N/A and I rebuilt it and converted the working engine With: -CP Neo forged pistons -Manley Rods -Garret Gt3071r DDB Turbo -Series 2 stock fuel rail and injectors -Series 2 exhaust manifold -SplitFire Neo coils - New iridium NGK Plugs -255 Walbro Fuel Pump -Freddy Forward Facing intake -Stock GTT R34 NEO Turbo ECU -Many Many more.... After my conversion build with all new parts, i primed it and started on the first Crank. CURRENT STATUS: -Crank and starts instantly every single time and runs only when applying throttle THE PROBLEMS - Sounds great however it if you do not apply throttle and leave her idle, she is struggle to breathe and stutters and will die - Jumps up and down the rev range by her self - Cannot find a decent idle and when she does its not for long - After reeving and she goes back down she dies - Sometimes when reeving she break up on her own SOLUTIONS/TROUBLE SHOOTING - TPS sensor needed to be adjusted to get the right Ohms. After we fixed it it seemed to be more consistent when reeving and staying and holding at an RPM's and slightly better idling. - Idle air Controller, adjusted the screw and tried over 10 positions, although it actually really helped idling it still did not cure the dying at idle problem and finding a good idle problem. NEXT STEP (tomorrow) Take a look at the base/ignition timing with a timing light to the notches on the crank pulley and adjust it with the CAS sensor? DOES ANYONE HAVE EXPERIENCE WITH IGNITION TIMING? HOW DO I DO IT PROPERLY? WHAT DO THE NOTCHES INDICATE? WHAT NOTCH DO I WANT TO BE AT? ANY ADVICE IS GREATLY APPRECIATED

Hi all, recently finished my rb25de+t conversion. Runs and drives perfectly - except after idling for about two minutes it shuts off like i have turned off the key, doesnt hesitate or run rough or blow smoke etc just turns off. Since the problem came up i have done the following, regapped spark plugs cleaned and adjusted aac valve checked battery terminals and terminals at both fuse boxes checked every small fuse in cabin and boot extra info for you which may help, im using the following parts stock gtst ecu stock 25de afm missing oxy sensor and light is on dash doesnt have an immobiliser. i cant think of anything that would shut it down so plain witout and issues or rough idling. thanks!

Pretty much as the title says, I have a 97 R33 and the engine does not like to idle comfortably. On start up and warm up it revs itself to 1.5 to 2k which I assume is pretty standard but once it is warm it will drop right down to 300 to 500 (going by the tach it might be slightly higher but not much) and feels like it's a Cummins instead of an RB. The worst part is rolling up to a set of lights, if I don't engine brake the whole way it will stall and I have to blip the revs whenever I have the clutch in. Once it recovers it will idle, but will feel rough (usually around 700, slow enough that the aircon doesn't really work, also another problem I have with the car, the aircon won't be cold lower than 1.2 to 1.5k rpm, I assumed this was a part of the previous issue). The exhaust also smells quite fuely. The car is pretty much stock apart from a front mount, BOV (which is set to full recirculation anyway) and a pod filter and always runs 98 I do plan on eventually putting a haltech or equivalent ecu once I find the funds but that could be years off so any help fixing this would be great, Thanks in advance Joe

So like i have an rb25det in a nissan laurel,and it has a transmission hooked up to it.since i bought the car it had an issue whereby when accelerating,the car seemed to be slow and sluggish,like if it was lacking air,and after a while it drived like normal,also it had an idle problem (only when in drive not park)the car would give a bad idle as if it had bigger cams,(not that it had any).This idle problem wasnt constant though,it happened randomly.But when the accelerator was floored it ran like a beast.however i recently had a problem when i put the car into reverse.immediately it would shut off.no bogging nothing just cuts off as if i turned the key off.i was wondering if yall could shoot some ideas my way.Thanks in advance

Hi Guys, I have a problem at idle with my GTR, cylinder number 5 is not running when idleing or not under load, When the engine get some load, it kicks back in and runs fine with plenty of power. I have replaced all 6 spark plugs, i have swapped over the coil packs with others and its not a coil pack issue. However when i Unplug the plug to the 5th coilpack, the revs don't change/drop. So I'm guessing it has something to do with the plug/wiring? Anyone got any advice before i start replacing everything? I recently replaced the whole engine and got it tuned. This started happening a day after i got it tuned. Took it back to the mechanics who installed the motor and they couldnt find the problem... Any help would be greatly appreciated!

Ok car was goin perfect but yesterday morning it suddenly had like no power when i accelerated, it would do the turbo wind up and all but just no power, later the car went weird wouldnt rev past 3.5 rpm, smoke coming out exhaust, hunting idle, misfiring. I replaced spark plugs, tested coils (splitfires), check aac valve, check for vacuum leaks checked maf, checked intercooler.. Things done before prob i adjusted boost and put 20 dollars prem fuel in car.... Please help im seriously stumped car has fc commander, splitfire coils, stock bov, pod filter etc. 1994 r33 manuel

Hi all. Tried to search for the issue, but I didn't have much luck finding anything relating directly to my issue. Car has a stock blow off valve, plumbed back. Decided to make a plate to block it off, you know for flutter/dose/compressor surge whatever you want to call it. Car runs great, starts fine, idles fine, holds boost, flutters... But if I am idling and rev it slightly, then take my foot off the throttle, it hunts for a while then goes back to idling fine. Sometimes it drops to 100-200 rpm, sometimes just to 600, stalled a couple times. It doesn't ALWAYS do it. It is mainly a concern when I am in traffic and need to move forward slightly. Black smoke also comes out the exhaust when hunting. Rich? Is it because it was tuned with the plumb back blow off and it is expecting that air for idle and isn't receiving it? I have blocked the vacuum line going to the bov and the plumb back pipe. I haven't tried plumbing the bov back in and taking out the blanking plate. Will do that soon and report back. R34 gt-t rb25det neo Garret low mount on 18psi avc-r boost controller power fc supporting mods

Hi i realise there is probally more than one problem but it would be awsome if i could get some ideas on what to check and fix to get my car back to normal Its a r32 gtst with nismo 740 injectors and a cold air intake but a universal fuel pump The issue is that the engine feels sluggish and wont idle even when it gets to its running temp then after a little while it comes good and runs almost perfect and it will idle also it will idle when you first turn on the car also the oil pressure gauge keeps goin down slowly

I recently purchased my non turbo skyline and its been acting up since day 1. I can't determine whats causing it because I know there are multiple things that cause the engine idle to hunt and the engine to die when the clutch is engaged.. I know something or multiple components need to be cleaned because this does not happen every time I come to a stop, it happens at random times. Also it normally never hunts or dies until the engine has warmed up. Just wondering what I should start with first.. I've already cleaned the Throttle Body and the AAC. Some help or lead way would be much appreciated!! -Mitch

hey guys, still trying to fix up the engine in my series 1 r33. picture 1: so i noticed on my greddy intake that there is 4 points that are blocked, i could not find anywhere that said what these were for and im very new to skylines and its got me screwed! if anyone could tell me what there for/ where to run them, if they are needed at all, would be great! picture 2: so my fpr is not rigged up? and i cant seem to find exactly how to hook it up? i seen some diy but even with them i found they were a bit hard to understand, like i said i am a noob, but like everyone you have to start somewhere and i would rather learn rather than just get it done somewhere, picture 3: i took my coilpacks out today to have a look over them and i noticed oil where the spark plug is, seemed odd to me, is that normal or? i was thinking that if its not normal i have a leaking gasket and oils finding its way there.

Hi guys, Been driving my 33 for a while now and it has been faultless. However the other week I was cruising at 60 and it felt like the engine power had dramatically decreased..almost cut off. I tried to push down the accelerator harder but the revs were struggling to increase and the car was in a jerky motion. I pulled over to the side and the idle was fluctuating from say 200, where the car would almost die, to 1200 rpm. After a few mins the care felt okay to drive again, but not 100%. Since then, if I don't use boost then the car will drive okay. Once I hit boost hard (1st gear pulls) and while im still in boost, it sounds like the turbo is whistling but the car isn't accelerating much. Then after this short spurt of boost the car will feel sluggish, jerky, and very minimal engine response from the accelerator. The car will end up regaining some power after a couple of minutes but not fully. Prior to this happening I had an aftermarket bov which I had to change back to factory. I thought it could be the issue so I changed it back to the aftermarket one but the car still acts the same. Fuel pump is a wallbro 255 and is fine...still primes when turning the ignition to ON. I'm still thinking it's some kind of fuel related issue. Maybe turbo has had it? Care to shed some light guys? Thanks for the help. EDIT: i have yellowjackets with the standard plugs that rb25dets use.. replaced the plugs only 2000kms ago

Yeah basically as the title has described. Revs up Decreases, Sometimes holds at 1100rpm momentarily and drops back to normal idle Other times drops back to normal idle no worries Such a weird little sticky point Any ideas? Anyone seen this before?. Video for more clarification. Cheers

RB25DE+T PFC idle Hey guys, Had this minor annoyance for a very long time, from memory probably since the powerfc was installed and tuned 6+ years ago. Maybe because I'm getting older it's starting to annoying me more. I turn the car on in the morning and idle is high, 1500-1700rpm, but stable. On the hand controller it all looks pretty stable, not sure if idle this high when cold is normal with other powerfc's but so far it doesn't annoy me. As I'm driving around and idling at lights while the car is still warming it's still sitting at 1500rpm, on the hand controller once the water temp gets to about 59-62 degrees it starts hunting, from 1500 rpm down to 900rpm and back and forth every 1-2 seconds and will continue like this until the water temp gets to about 72+ degrees then idle is perfect, 850-900rpm. The only way to control it during this time is let off the clutch a little bit until it bites and slowly lower the revs, then I slowly press my foot down on the clutch again. If I put my foot down too quick on the clutch or roll forward a little the hunting starts again. Only happens when the car has been sitting for a long time, eg overnight or all day and then come back from work and turn it on. If the car gets to operating temp and then I turn it off for 1-3 hours and the engine is still pretty warm no issue, idle is perfect. Now before I start playing with the TPS voltages and mucking around pulling apart things I'm wondering if this is just something in my maps in the low load/idle section that needs adjusting as it only happens for ~10 degrees so I would have guessed the voltages on the TPS are fine? Car has been tuned a number of times many years ago by a very reputable tuner. It happened as soon as I swapped the standard ECU to the powerfc and it has been like this ever since, even with adding in cam gears and a z32 AFM. I have used contact cleaner to clean the AFM and I've cleaned the AAC with throttle body cleaner and ear buds in every little knook but no avail. Any suggestions? I've found this post from long ago which seems almost identical so I'll give turning off O/2 feedback a go (not sure if it's enabled currently or not) but wanted to see if others had the same issue? Thanks.

Help me diagnose high idle Cant figure out my idle issue. When I got the gtr, the issue already existed. So: Cold start idle: 1200 Warm idle: 1600 after driving for a while: 1800 While driving, between shifting, idle drops to 1000 than jumps back to 1800 in neutral. I pretty much closed the IAC valve and had minimum effect. I want to try everything else before I open the intake manifold and check if the film is there there. TIA!

HELP PLZ! R32 GTR Idle gets lumpy when car is hot. Hey guys my apologies for starting an other idle thread.But I have been searching for a few days and can't get an exact answer. the car is a 91 GTR with very light mods. N1 apexi exhaust up to the stock front pipe. Hashimoto radiator Yellow Jacket coil packs hks oil filter relocation kit and HKS pod intakes Recently replaced my AFMs with APH AFMs The Problem- the car has been running fine for the last two months but recently I was losing power and throttle along with the idle starting to sputter at random times. I was certain it was the dated AFMs. So replaced them with a aftermarket brand from cananda. The problem seemed to go away (so I thought).After driving the car around for about 30 minutes and allowing things to get warm the car just flips a switch and the idle will run shitty and it sounds like a go kart accelerating. Wondering if it could be faulty coilpacks or spark plugs. On a good note the car doesn't lose or cut out in acceleration anymore. When I cold start he vehicle it runs fine until things get hot after a while of driving for the day. Then I'll restart the car and have the same lumpy idle issue. Any idea what can be going on fellas?

Power FC problems (sr20) Hello guys, I am new to this forum. I am just your average 21 year old dude who bought a Nissan 200sx S13 with a SR20DET and I did some modifications. I assume this is gonna be a long post, but please bear with me. So I started my car after 1.5 years and during those months I bought several parts. (Apexi Power FC Djetro, S15 turbo, 555cc nismo injectors and different things but that wont matter) Anyway, 2 days ago I started her up and it went great, except for getting the car to idle. It just WON'T idle at all. I found out that my injectors had the wrong latency. I did 66% and 0.72ms and it should've been 66% and 0.10ms? So I changed that and after a few resets and start ups it went great. First 10 minutes idle, amazing. 800-900rpm, car not shaking. Then I had to turn on the A/C which I dont have. I thought using the climate control and do some cold air would do the trick. Well I guess not. Car was doing weird things. 480rpm-900rpm over and over, here is a video; https://www.youtube.com/watch?v=GZXVeiSi1y0 I don't know what to do. My map sensor and IAT are working fine. The car was idling fine but I had to complete te self-learning process. My defroster doesn't work either because some cables are missing. (I found some cables so I am gonna try it out tomorrow, it might work) Other things that you guys might find interesting; My O2 sensor stays at 0.0v, even at idle. I found out today that there is a fat O2 sensor in the elbow, and the redtop ECU uses a Skinny O2. (I had a black top ecu, so this is why there is a fat o2 in there. Black top = fat o2 || redtop = skinny o2) Can it be because of this? How much influence does the O2 sensor have when it comes to the self-learning process? Also, the car starts with boost control on. And I don't even have a boost controller. (I turned it off) My mod list: 555cc nismo gt28 turbo Apexi Power FC D-jetro Apexi powerfilter aftermarket IC HKS wastegate Mishimoto rad AEM Wideband (haven't hooked it up yet, I don't know much about this thing. But it was necessarry for tuners?)

M35 rough idle / shudder Hi, I've recenly had problems with the car and would like to know if it sounds familiar. Symtoms : - Rough idle : the car does not stall but you can definitely feel a shudder - Shudder also present when driving, especially around 2000-2500 rpm Coming from the engine 100%, it is less noticeable once the turbo kicks in but there is a slight power loss too. Problem has increased in intensity when I was driving it home. If someone could point me in the right direction that would be great. Mechanical skills close to null, if someone around Sydney is keen to have a look at it, I'd obviously pay for your time, but I can of course try a few things on my end too. Cheers!

Hey guys hoping I can make this quick and easy and get my car running to it's full potential. I've got a 1993 r32 manual, turbo, rb20, has basic starter mods as in intercooler and exhaust, coil packs. When i turn the ignition and start her up she will start very well, idles around 900rpm. As soon as she hits running temperature she runs like a complete pig, idle goes from 900-300 and is constantly jumping from one to the other. I took off the auxiliary air control valve, cleaned her out and still doing it. Has aftermarket coil packs but not sure on brand (they're purple?) but haven't tested them yet, going to check my spark plugs this week also. I put new silicon vacuum lines on and hopefully got them all. Air flow meter had a hole in the mesh but not sure if that'll make a difference, so i just bought a new one which i'm about to chuck on after i spray it with some contact spray. Please help, driving me insane, just want to drive her again.

Ok, so as of Tuesday last week I've now got an idle issue and despite searching the forums I'm not quite sure the cause, so am hoping for some imput and ideas. The Problem What will happen is when I start the car (typically from cold) it will be ok for a minute or so, then anytime I'm in neutral the idle will be hunting, going down as low as 200 and up to around 800, like a pendulum. If I'm driving with higher revs when I get into neutral the drop and swing of revs will be harder and it will be on the verge of stalling. It will eventually close the range of revs until it gets to the 800 idle the car is set at. The longer I drive it the less it will hunt until eventually, say after 10 mins of city driving it will idle normally. Also, using AC or brakes doesn't appear to affect this issue. Some specs R33 GTST bigger turbo, 740cc injector, FMIC, exhaust, Z32 AFM, Walbro fuel pump and a Tune in December. All of these parts were bought and fitted new within the last year. In addition here are some common things to check regarding a poor idle that I've already considered. - AFM poor soldering (unlikely as is a new unit) - Vacuum/ IC piping - checked and were ok, and many have been replaced with silicon anyway - ACC clean - done - Fuel filter - replaced - Plugs - 1 month old - O2 sensor - 9 months old - Coil packs - original, but are in good condition (and I don't think this issue relates to them anyway) - Water temp sensor - original What I think It might be Seeing as my problem seems to be the regulation of air while the throttle body is closed, I'm thinking it could well be part of the Idle Air Control Valve system that is causing this. From what I can see there are two main parts, the popular one that people seem to talk about being the ACC valve. While I have cleaned the IAA unit (That's the wad hanging off the inlet manifold that contains the ACC, the cylinder hanging off the side) has anyone heard of that ACC unit being faulty or failing? Could it be a case of swapping this out? The other suspicion I have is that it might have to do with the Air Regulator, which is the unit located below the IAA unit and connected by a vacuum hose (which continues back into the inlet plenum). According to the manual the air regulator is fully open below 20 degrees, half closed above 20 degrees and fully closed at above 60 degrees of water temp. This would seem to correspond to the times in operation that I will typically have this problem. Has anyone had this unit fail at all, or could it be cleaned back to good health? And aside from this, is there anything that I may have missed which fits the symptoms of my idle problem? Ok, thanks all