R33 New Idle Problem Need Help!

[Bjc3000]

Hi all,

It's been a while since i've last posted, as all the issues with the car were worked out and it was running great.

However. :'( in the last few days my car has basically decided idling wasn't it's thing and is refusing to do so. i have no idea why.

Normally it would start, rev to about 1100-1200 rpm, then drop down to around 7-850 and stay there. running reasonably well. it did have issues with hard decel and having the revs drop dangerously low. but it never stalled on me. ever.

For any issue with my car, i always check here first, it's been a wealth of knowledge. i've searched the forums. believe me. 8 hours straight yesterday hunting the forums and 3 hours this morning. i've seen a dozen threads here with similar issues, however they mostly tend to be when warm. mine is straight from stone cold.

Now, on cold start, the car starts up. revs around 800-900 rpm. hunts a bit. farts around. drops dangerously low to 300rpm. and hunts. it will go anywhere between 300 to 6-750. and even sometimes it will straight up stall out.

I have a video i'm currently uploading to youtube i'll post and it shows the issue.

Just so i can start clear in my head.

The car is modded.

Aftermarket Bov (Recirc Bov, not Atmo)

FMIC

Bigger Turbo

Stock airbox

Z32AFM

2.5" exhaust

Things i've Tried.

New Spark Plugs. - Made no Difference

Pulled Afm and cleaned with Maf Cleaner - No difference. ( however before this issue i could unplug the afm and it would run. shitty but it would run. Now the car just dies. )

Tested TPS - (Reading 0.45 at idle going up to 5v at WOT) seems ok. - disconnect this and the car stalls out as well.

cleaned air filter

Things i'm looking at trying

- aac valve clean.

I don't know if it's the o2 Sensor, i've read that it's only used when out of cold start, as for for the coolant sensor, the issue present straight away at cold.

I've got Splitfires running with a new set of plugs. shouldn't be a spark issue.

I've heard vac leaks could be a problem, but i was under the impression that it would be sucking in more air and revving higher at idle moreso than chugging and stalling out.

any thoughts? anyone with a similar experience. like i said. and please note this. The car, the tune, everything was Running Perfectly for about a year up until about 3 days ago. then all hell broke loose. I wanted to reiterate that as nothing on the car has changed, no new mods, anything. the BOV has been on for that entire period as well. it has stock ecu, but is only running stock boost. it was dyno'd running fine.

any ideas !?!?

I'll post up the link as soon as it uploads.

EDIT: Here is the link to the video https://youtu.be/c4ZRyFF-JTs

Cheers

Brendan

Edited December 27, 2015 by Bjc3000

[Bjc3000]

Just checked the ECU for fault codes, showing 55 - all clear. this is driving me crazy. going to go pull the AAC valve off and have a look..

[Ben C34]

Its the aac

[Bjc3000]

funny you should say that.. just pulled it off now, and it needs a good clean i believe..

I'll post back and give a heads up how this aac clean goes. off to get some carby cleaner.

Hopefully this helps out the decel rev problem as well.

[Bjc3000]

Have completely cleaned out the aac and refitted, on first start it revs a bit higher now, but after a minute or two it goes back to doing what it was doing previously.

I'm stumped at this point as to what it could be, I'm reading 12.04 volts at the battery.

I've done the plugs and the coilpacks are still very new. don't seem to be showing any wear at all.

i can't quite put my finger on what might be causing this.

It revs fine, it pulls as hard as ever, not missing or popping. just has the dodgiest idle known to man. and only recently.

at low speed and when i put my foot on the brake or turn it threatens to die almost every time.

it only ever did it once in a blue moon before.

So now i've cleaned the AAC are there any tests i can do to determine the cause? pulling plugs from different sensors etc until it cuts that shit out?

could dirty fuel cause this to happen?!

just for the record. sometimes i'll start it, and it will idle perfectly. no hunting. no nothing just straight up 750 as it always was. doesn't miss a beat. then other times i'll get what i had in the video.

erratic, up and down hunting.

but now every time i drive it, it tries to choke out splutter and die at low speed.

The most frustrating thing ever.

[Kustom20]

It almost sounds like air leak - but if the vehicle run better than ever then its obviously not having boost leak issues - and when the vehicle is revved a bit it balances out with fuel compensating for the smoother AFR level - but at idle decel closed throttle steering and brake it has trouble.

I would have also said IAC/AAC maybe sticking as it controls the air flow for idle at closed throttle - but if you have checked this and cleaned it out that should eliminate it being the issue.

For it to be sporadic idle at cold start or low revs and decel tends to lead towards AFR issue - brake would add air through booster and steering adds idle through power steering sensor. So with this if their is already excess air being added to the inlet and when you push the brake pedal - a bad booster will cause idle issues but it would be constant bad idle and you would no doubt hear the hissing sound.

Has the vehicle been re-tuned after the Z32 was installed? On the MAF have you got the Ground to Chassis and Ground to Signal Ground - its probably had this running perfect for ages but just checking - as I have had a few tuners mention about connecting incorrect ground and works for a bit but can cause issue eventually. And some users of power fc sticking to the base AFM setting 3 for the Z32 and it needs to have a better air flow curve based on different vehicle mods.

How long ago did you replace the fuel filter? - I know some have removed their fuel filter and couldnt even blow through them

Has the vehicle ever had a fuel issue? and has the fuel pump been replaced or upgraded? Again its hard to believe this could be an issue as its only at cold start and not always

Do you have an after market ECU - if you could log the idle to see the numbers that would be great - we could take a look at your air flow vs other to see the values.

Maybe your AAC valve is sporadically on its way out

[Bjc3000]

Hey mate thanks for your reply.

it has a bosch 040 fuel pump and its never had any issues. the fuel filter was done on the last service less than 6 months ago.

my 33 is an auto. it has a stock ecu but it got a toshi chip tune for 16psi and the z32 afm.

it originally had a greddy emanage piggybacked but it was causing the car to misfire a lot. we took it out and turned the boost down a bit. its mostly stock again.

i can't get any numbers at this stage.

i was thinking that a vac leak would increase my rpm at idle? ive searched and everyone points to iac valve or maf.

my idle hunts a bit, 100 to 200 rpm.. but it slowly gets lower until it conks it. used to only happen on a hard decel. but it would never actually die. the lowest it would get to 300rpm. if i was paying attention and slowed without braking hard it wouldnt do it.

now it happens everytime. and as you see in the video it will idle right then just drop. hunt. catch again. drop. it adds idle when you turn the steering wheel. putting your foot on the brake makes it drop rpm.

I've read so many forum posts now. in the hundreds. and nothing I've found quite shows the same issue im having.

[Bjc3000]

little update. i decided to test my afm signal readouts this morning. got out the multimeter and started the car. it was idling fine. so i let it warm up. it was holding steady no hunting or anything.

pulled off the stock box and found 12v to afm etc.

i couldnt get my probes into the connection without damaging it so i left it.

when i put my box back on. i was doibg up the clips. one of the clips was being a bit of a pain so i had to give it a bit. wheb it clipped in the car soluttered and shat itself. revs dropped. then went up to a thousand than back down and spluttered again.

i didnt think that was right so i took the box off again. tappung yhe edges aroubd the afm gave the same thing it would splutter and die.

this isnt right? is it? i mean if i hit a bunp in the road it would be enough to upset it in the same way. maybe the joints are dodgy? I'll look into it further

also as another note. i can't disconnect my tps. when warm. if i disconnect the tps. the car dies. shouldn't it continue to idle? as this is the process for adjusting the idle screw? thats pointing me back to the afm being shagged.

if i disconnect either of the iac valve solenoids i get no noticable change in rpm

which concerns me as well.

my car is driving me up the wall. suggestions in the afm? seem faulty to anyone? like i said it was idleing fine up untill i bumped the afm. i think it might have shat itself.

[Bjc3000]

sorry for the typos. on my phone and fat fingers.

[Kustom20]

I would start with the easier less expensive tests

Definitely check those wiring connections - yeah something seems a bit of a miss with your wiring either connections and hopefully no wires are starting to melt and touch if any of the wires or connections on the AFM were cutting in and out then it would definitely cause the car to want to stall -

If the AFM has 12v power - Signal - Signal Ground and the main ground wasn't connected the car would still start and simply stall straight away. If there was a bad connection for the main AFM Ground then it could possibly cause it to cut in and out almost to the point of stalling.

Just a note that the twin core AFM cable that runs from R33 RB25 ECU to MAF has a metal sheath heat protecting coating as well and the 2 small signal wires that run through this from MAF to ECU if overheated can actually ground through the sheath - I ran continuity tests from ECU from memory on the ECU end the signal cable is a bullet connector - to the ends of the wires on one vehicle and the sheath had actually grounded the signal - didnt cause any damage but just didnt allow the vehicle to keep running - it simply started and stalled - started and stalled - so the continuity test found the signal was actually grounding from ECU to the MAF end of the cable. These are also subjected to heat along the chassis rail/shocker tower area - and in the R33 the the o2 sensor cable also runs in this section of the loom - when ever we get an R33 in we always check this area for heat damage

As for the TPS this just sends the ECU the voltage for throttle position should be 0.45v closed throttle or there abouts and up in the high 4.87v for wide open - the IAC is what controls air flow for closed throttle as the butterfly on the throttle is fully closed so the piston in the IAC will move up and down depending on how much air is needed for the vehicle to idle at the RPM setting in ECU

The idle control valve simply gets air from before the throttle body. But if the internals are sticking then it could be an issue - even after a carby clean spray just doesnt fix a bad one.

If you have a friend who would lend you some parts to test with then you could simply go through each part - AFM IAC TPS etc until you source the issue. If I were close to where you live I would be more than happy to drop in and we could test your parts.

[Bjc3000]

hey mate thanks for the reply.

i live in hervey bay qld. dont know whereabouts you are. thanks for the offer.

I've tested tps. it's given accurate readings for closed and WOT.

like i said i couldn't check output voltages of the maf because i recently moved and all my shit is everywhere.

i cleaned the iac and tested solenoid on 12v seemed ok.

sometimes the car starts and idles fine. i found that it would go to shit as soon as i started driving.

like i said I've got a video where i tapped the airbox just above the afm and the car instantly chugs. im thinking dry solder joints is the problem and as soon as i start driving and there is a bit of a vibe or bump the afm starts throwing out bullshit values to the ecu.

i put the car on carrier and sent it up to my tuner to have a look at.

getting all vac lines replaced, getting a new afm if i can and getting him to test everything. fuel pressure. vac lines. comp and turbo play. anything he could think of im getting done.

im almost 100% positive its the afm but ill have everything tested to be safe.

when we did the engine replacement the mech didnt change the injectors over onto the new motor and they subsequently sold with the old block. so I've had to take the boost back to almost stock.

also getting new injectore and cranking the boost back up to 19psi. going to drive a lot harder when i get it back.

I'll keep you posted. thabks for the responses

[Kustom20]

hey mate thanks for the reply.

i live in hervey bay qld. dont know whereabouts you are. thanks for the offer.

I've tested tps. it's given accurate readings for closed and WOT.

like i said i couldn't check output voltages of the maf because i recently moved and all my shit is everywhere.

i cleaned the iac and tested solenoid on 12v seemed ok.

sometimes the car starts and idles fine. i found that it would go to shit as soon as i started driving.

like i said I've got a video where i tapped the airbox just above the afm and the car instantly chugs. im thinking dry solder joints is the problem and as soon as i start driving and there is a bit of a vibe or bump the afm starts throwing out bullshit values to the ecu.

i put the car on carrier and sent it up to my tuner to have a look at.

getting all vac lines replaced, getting a new afm if i can and getting him to test everything. fuel pressure. vac lines. comp and turbo play. anything he could think of im getting done.

im almost 100% positive its the afm but ill have everything tested to be safe.

when we did the engine replacement the mech didnt change the injectors over onto the new motor and they subsequently sold with the old block. so I've had to take the boost back to almost stock.

also getting new injectore and cranking the boost back up to 19psi. going to drive a lot harder when i get it back.

I'll keep you posted. thabks for the responses

Yeah thats the best way - if your confident with the sensors then hopefully the tuner just needs to fix some minor probs and get it all 110% running great and be safe for driving at high loads.

Definitely keep the posts coming its great to see issues being fixed for other users to read.

And yeah heading up to Sydney next Tuesday then Summernats on way back - live in Vic so Hervey Bay is a fair travel lol

[tridentt150v]

Look up dry solder joints on AFM..........there is a thread on this. Not saying its your problem but a few ppl have had to take their AFM apart and re solder the joints.

I've never had to do it....just know it exists

[SMiTHBRo]

Have you tried running it with the o2 sensor unplugged? An easy way to check an o2 sensor is to remove it, hold the sealing washers and give it a shake, if you hear a rattle, it's a goner.

I would also be looking for vacuum leaks and split intake/intercooler hoses.