Jump to content
SAU Community

Cold Start Issue

kidafa

By kidafa,
in Four Door Family & Wagoneers

 Share

Recommended Posts

QWK32 Veteran

QWK32

Posted
Posted (edited)

sorry, lol

ok, those links you have put up, one is for cleaning the AAC valve, which all the RB motors have. it controls/stabilizes engine rpm during normal idle, cold start, when the air conditioner is turned on, etc.

the second link you put up is for the Air Regulator, which is on the RB20. this valve also helped to stabilize idle and with cold starts. i dont think any of the other RB engines had one. the RB25 NEO doesn't. you can check to see if this is also the case with the R33/S1 by looking under the throttle body and see if you can see an Air Regulator valve like is shown in the second link you posted up, but i think its just a thing they had on the RB20.

so on the older RB20 there were 2 valves to control idle. on the newer RB25's there is only one valve to control idle, nissan just left the AAC valve to do all the idle control. the AAC valve is also refered to as the IAC valve.

so if you want to clean the valve that controls idle clean the AAC valve on the back on the inlet manifold (the first link you previously posted). but keep in mind that this valve is designed to control/stabilize idle on an already running engine. you may get a better start after cleaning it, but the main reasons you clean the AAC valve are, if your idle is too high or too low, or if you engine idle hunts around, say it jumps around between 600-1200 rpm for example. you idle is low, as in its barely turning over, thats too low for the AAC valve to recover.

p.s. i know the exact problem you have, my old 32 used to do it, i cleaned all these valves and it didn't really help it, still had to tap the accelerator to get it going.

Edited by QWK32
  • Replies 57
  • Created
  • Last Reply

Top Posters In This Topic

Popular Days

Top Posters In This Topic

Popular Days

Posted Images

_Ryan_ Grand Master

_Ryan_

Posted
Posted
sorry, lol

ok, those links you have put up, one is for cleaning the AAC valve, which all the RB motors have. it controls/stabilizes engine rpm during normal idle, cold start, when the air conditioner is turned on, etc.

the second link you put up is for the Air Regulator, which is on the RB20. this valve also helped to stabilize idle and with cold starts. i dont think any of the other RB engines had one. the RB25 NEO doesn't. you can check to see if this is also the case with the R33/S1 by looking under the throttle body and see if you can see an Air Regulator valve like is shown in the second link you posted up, but i think its just a thing they had on the RB20.

so on the older RB20 there were 2 valves to control idle. on the newer RB25's there is only one valve to control idle, nissan just left the AAC valve to do all the idle control. the AAC valve is also refered to as the IAC valve.

so if you want to clean the valve that controls idle clean the AAC valve on the back on the inlet manifold (the first link you previously posted). but keep in mind that this valve is designed to control/stabilize idle on an already running engine. you may get a better start after cleaning it, but the main reasons you clean the AAC valve are, if your idle is too high or too low, or if you engine idle hunts around, say it jumps around between 600-1200 rpm for example. you idle is low, as in its barely turning over, thats too low for the AAC valve to recover.

p.s. i know the exact problem you have, my old 32 used to do it, i cleaned all these valves and it didn't really help it, still had to tap the accelerator to get it going.

correct but apparently there is also a cold start valve under the plenum, in the RB25 guide and according to 2mechanics.

66yostagea Grand Master

66yostagea

Posted
Posted (edited)
had the same problem with my r34 GTT. turns out it was the spark plug spacings. weird but worked a treat.

I'd rather clean the AAC (IAC) before doing the plugs. Need that front facing plenum.

No wonder my first thread did not get going. This is mass confusion.

Edited by 66yostagea
BensDR30 Experienced

BensDR30

Posted
Posted

lol!

I haven't checked in FAST, but I am assuming that the solenoide adjacent the AAC/IACV is some kind of FICD?

If so, that may be worth checking too, as it may be active during cranking.

When my S1 was acting in a similar manner (including the idle dropping right off when slowing to a stop - even on a hot engine) I looked at 3 things;

The O2 (which was known as dodgy, and replaced)

The plugs (which were 'compliance' Autolite and replaced with NGK Platinums)

The AAC (but I only removed the control motor from the housing via the 2 screws & gave it a wipe over)

The symptoms of a slow cold idle, flaky hot idle, and occasional cold stall were cured.

In the last couple of weeks I have had a momentary slow cold idle occur once or twice - but that could be due to me letting go of the key a fraction too early. I may check the AAC to see if it has gummed up, but can confirm that it is providing a wide range of engine speeds via testing through Consult control (the opening can be manually set in DataScan).

PS Chris, I'll probably only work a 1/2 day tomorrow, so should be around in the arvo if you want to look at your car then.

QWK32 Veteran

QWK32

Posted
Posted
lol!

I haven't checked in FAST, but I am assuming that the solenoide adjacent the AAC/IACV is some kind of FICD?

If so, that may be worth checking too, as it may be active during cranking.

i think your right there Ben but looking at this diagram it says it is activated by the A/C.

post-34711-1249472667_thumb.jpg

BensDR30 Experienced

BensDR30

Posted
Posted

Fair enough - I'm without technical resources right now

(I expected the air con to be the only situation, but couldn't be sure)

An Air-reg is certainly shown on that diagram, and they are there only for cold running - I thought that the AAC/IACV had completely replaced that function, but it seems it's still used on some '25's at least...

If your air-reg is crook (jammed closed), then you won't get a fast cold idle, declining over time as the bimetallic strip closes the port.

If it's jammed open, then the idle will be too damn fast when warm.

I'm considering disconnecting the Air-reg heater on my FJ, as the idle drops of a little too fast when it's stone cold.

QWK32 Veteran

QWK32

Posted
Posted (edited)
An Air-reg is certainly shown on that diagram, and they are there only for cold running - I thought that the AAC/IACV had completely replaced that function, but it seems it's still used on some '25's at least...

yes, and on the same style diagram in the R34 workshop manual the Air regulator is apart of the AAC. so the R33/S1 RB25's still have a separate air reg but on the Neo RB25's it has been combined with the IAC-AAC valve.

Edited by QWK32
_Ryan_ Grand Master

_Ryan_

Posted
Posted
ok so theirs no real point cleaning the back valve as its idling sweet once its going.....

Ryan when are you going to hunt it down on your car?

what shall i do :rant:

Either when I have time or the wallet recovers from two lots of reg and one lot of insurance and one lot of fixing a 32 is done :)

lol!

I haven't checked in FAST, but I am assuming that the solenoide adjacent the AAC/IACV is some kind of FICD?

If so, that may be worth checking too, as it may be active during cranking.

When my S1 was acting in a similar manner (including the idle dropping right off when slowing to a stop - even on a hot engine) I looked at 3 things;

The O2 (which was known as dodgy, and replaced)

The plugs (which were 'compliance' Autolite and replaced with NGK Platinums)

The AAC (but I only removed the control motor from the housing via the 2 screws & gave it a wipe over)

The symptoms of a slow cold idle, flaky hot idle, and occasional cold stall were cured.

In the last couple of weeks I have had a momentary slow cold idle occur once or twice - but that could be due to me letting go of the key a fraction too early. I may check the AAC to see if it has gummed up, but can confirm that it is providing a wide range of engine speeds via testing through Consult control (the opening can be manually set in DataScan).

PS Chris, I'll probably only work a 1/2 day tomorrow, so should be around in the arvo if you want to look at your car then.

Yeah, cleaning the IAC would fix the stalling when braking issue... but not cold start.

kidafa Veteran

kidafa

Posted
  • Author
Posted

must thank Ben massively to coming over and plugging into my stag today with datascan.

Nothing seemed out of the ordinary which is good, but we couldnt find the cause 'cos of this. Might give the two vavles a clean in the not to distant future to see if it clears up. Its not going to be cold for much longer anyway so I might just wait.

Once again thanks Ben, was good to put another face to a user name :down:

BensDR30 Experienced

BensDR30

Posted
Posted

Only too happy to help - and wouldn't you know it; After flushing the coolant and replacing the thermostat tonight (preventative maintenance), my car ran slow and stalled on the first start...

The second attempt was a slow runner too, but it picked up.

Jinxed!

BensDR30 Experienced

BensDR30

Posted
Posted

Mine was shite today too - and I was watching the Consult data when I started it to see what was going on.

The AAC went to 99 (full open) during cranking and below normal idle, but it wasn't enough... I started the car again and noticed that even once it did flare it was only at ~1100rpm, so I'm leaning towards the air regulator being partially closed (AAC kept it going at a value of 80 the 2nd time). So the next time I'm feeling like hurting my hands and lamenting how easy it would be to remove with the engine out, I'll try to test & clean it!

:)

  • 1 month later...
JAP-JET Collaborator

JAP-JET

Posted
Posted

Did you sort your issue out? I was having the same issue with mine for ages, put the factory bov's back on and it seemed to fix it, but when i put the aftermarket items on the car i never blocked off the pipe that fed into the intake pipes which im guessing was the problem sucking more air into the engine than the the two afm's were reading. As mine is an autech it may not be the problem your suffering but might be a thought for you to check, if you have put aftermarket items on the car.

Ads

BensDR30 Experienced

BensDR30

Posted
Posted

It's an intermittent issue for me, and generally not a major problem. On the coldest mornings, I simply hold the start position for a fraction longer to have a higher cranking speed. That seems to fix it (I'm used to the work car which effectively has a start switch, so 'cranking' a car until it starts isn't something I do very often :P)

Any intake leak will cause incorrect AFR's and poor running. I'm happy I don't have any such leaks.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • oHBoy.
      Starter motor replacment teeth count.

      By oHBoy. · Posted

      I had 3 counts over the last couple of weeks once where i got stranded at a jdm paint yard booking in some work. 2nd time was moving the car into the drive way for the inspection and the 3rd was during the inspection for the co2 leak test. Fix: 1st, car off for a hour and half disconnected battery 10mins 4th try car started 2nd, 5th try started 3rd, countless time starting disconnected battery dude was under the hood listening to the starting sequence fuel pump ect.   
    • GTSBoy
      Mistakes were made, my R34 Story

      By GTSBoy · Posted

      This. As for your options - I suggest remote mounting the Nissan sensor further away on a length of steel tube. That tube to have a loop in it to handle vibration, etc etc. You will need to either put a tee and a bleed fitting near the sensor, or crack the fitting at the sensor to bleed it full of oil when you first set it up, otherwise you won't get the line filled. But this is a small problem. Just needs enough access to get it done.
    • suko
      J50 clock date suddenly reset to January 1

      By suko · Posted

      The time is always correct. Only the date is wrong. It currently thinks it is January 19. Tomorrow it will say it is January 20. The date and time are ( should be ! ) retrieved from the GPS navigation system.
    • MBS206
      Mistakes were made, my R34 Story

      By MBS206 · Posted

      Buy yourself a set of easy outs. See if they will get a good bite in and unthread it.   Very very lucky the whole sender didn't let go while on the track and cost you a motor!
    • Kinkstaah
      Mistakes were made, my R34 Story

      By Kinkstaah · Posted

      Well GTSBoy, prepare yourself further. I did a track day with 1/2 a day prep on Friday, inpromptu. The good news is that I got home, and didn't drive the car into a wall. Everything seemed mostly okay. The car was even a little faster than it was last time. I also got to get some good datalog data too. I also noticed a tiny bit of knock which was (luckily?) recorded. All I know is the knock sensors got recalibrated.... and are notorious for false knock. So I don't know if they are too sensitive, not sensitive enough... or some other third option. But I reduced timing anyway. It wasn't every pull through the session either. Think along the lines of -1 degree of timing for say, three instances while at the top of 4th in a 20 minute all-hot-lap session. Unfortunately at the end of session 2... I noticed a little oil. I borrowed some jack stands and a jack and took a look under there, but as is often the case, messing around with it kinda half cleaned it up, it was not conclusive where it was coming from. I decided to give it another go and see how it was. The amount of oil was maybe one/two small drops. I did another 20 minute session and car went well, and I was just starting to get into it and not be terrified of driving on track. I pulled over and checked in the pits and saw this: This is where I called it, packed up and went home as I live ~20 min from the track with a VERY VERY CLOSE EYE on Oil Pressure on the way home. The volume wasn't much but you never know. I checked it today when I had my own space/tools/time to find out what was going on, wanted to clean it up, run the car and see if any of the fittings from around the oil filter were causing it. I have like.. 5 fittings there, so I suspected one was (hopefully?) the culprit. It became immediately apparent as soon as I looked around more closely. 795d266d-a034-4b8c-89c9-d83860f5d00a.mp4       This is the R34 GTT oil sender connected via an adapter to an oil cooler block I have installed which runs AN lines to my cooler (and back). There's also an oil temp sensor on top.  Just after that video, I attempted to unthread the sensor to see if it's loose/worn and it disintegrated in my hand. So yes. I am glad I noticed that oil because it would appear that complete and utter catastrophic engine failure was about 1 second of engine runtime away. I did try to drill the fitting out, and only succeeded in drilling the middle hole much larger and now there's a... smooth hole in there with what looks like a damn sleeve still incredibly tight in there. Not really sure how to proceed from here. My options: 1) Find someone who can remove the stuck fitting, and use a steel adapter so it won't fatigue? (Female BSPT for the R34 sender to 1/8NPT male - HARD to find). IF it isn't possible to remove - Buy a new block ($320) and have someone tap a new 1/8NPT in the top of it ($????) and hope the steel adapter works better. 2) Buy a new block and give up on the OEM pressure sender for the dash entirely, and use the supplied 1/8 NPT for the oil temp sender. Having the oil pressure read 0 in the dash with the warning lamp will give me a lot of anxiety driving around. I do have the actual GM sensor/sender working, but it needs OBD2 as a gauge. If I'm datalogging I don't actually have a readout of what the gauge is currently displaying. 3) Other? Find a new location for the OEM sender? Though I don't know of anywhere that will work. I also don't know if a steel adapter is actually functionally smart here. It's clearly leveraged itself through vibration of the motor and snapped in half. This doesn't seem like a setup a smart person would replicate given the weight of the OEM sender. Still pretty happy being lucky for once and seeing this at the absolute last moment before bye bye motor in a big way, even if an adapter is apparently 6 weeks+ delivery and I have no way to free the current stuck/potentially destroyed threads in the current oil block.
×
×
  • Create New...