Idle issues.....

[B-Man]

Hi all,

My Microtech LT12 busted - so I managed to work out what was wrong with my PFC and Q45 AFM - so I got that working now.

However, after going back to the PFC - I get a strange problem when the car revs to say 4000 RPM then back down to idle - it will stall.

If the revs come down slowly - it's OK - just when the revs come down quickly - it will try to maintain idle but stall.

I've taken it to a tuner who says the PFC settings are OK - there is something else wrong.

Have changed spark plugs and fuel filter , etc - cleaned the AFM.

I've tried adjusting the throttle body stop and idle control valve in many combiniations -

The only thing that works is to keep the revs at idle at 1300-1400 - which is silly.

Once at idle - it seems to be fine - 900 RPM - stays there rock solid, no hunting or anything.

Its just when the revs come down quickly from > 4000 RPM it will stall.

I thought it might have something to do with the lightened flywheel. But it worked Ok with the microtech (however I don't really know how the Microtech was tuned)

Anyway - if you have any ideas - let me know...

Cheers,

[ace_nz]

if youve adjusted the throttle stop you will have altered the tps voltage, set the throttle stop so the butterfly is completely shut, and make sure the idle contacts in the tps are goin shut at idle. Adjust idle speed with idle air control bypass screw.

[T0nyGTSt]

You have cams?

Set the idle a bit higher.

You have BOV?

Mine idled like shite with 2 HKS valves.

Went back to stock.

Install a HKS EIDS?

T.

[B-Man]

Yes to Cams - Tomei 256/9

Yes to BOV

But they were there when the PFC worked OK - (ie before HKS 3040 and Microtech)

What's HKS EIDS ???

Might be Cam gear - I was told that with Tomei cams - the cam exh cam gear needs to be set to 0 - mine is not - I bet that what it is ......

[DoughBoy]

What are your cams set at? I doubt it could be the cams, mine were slightly out and it still belted out decent power and drove perfectly. It could be the blow off valve being a little leaky? Was the BOV the same before the setup too?

[Roy]

electronic idle * stabiliser, basically plays silly buggers with AFM signal to stop stalling with atmo BOVs, and also helps with reversion and big turbos with cars running AFMs and modified inlet tracts/acoustics

[T0nyGTSt]

http://www.google.com.au/search?q=hks+eids...-8&start=0&sa=N

http://edgetuning.co.uk/product.html?id=hk...gory=elecothers

http://www.greenline.jp/catalogue/bblist.php?brand=HKS

It's a doo hickey that 'electronic idle stablises'.

It's a bandaid IMO because the FC should do it fine but it's useful on save extreme tune cars.

T.

[B-Man]

Actually - yeah - it might be the BOV. I recall that it did this (not to the extent that it does now though) before the 3040 went on .

Interested to hear from Steve - did/do you have this probelm ?

I recall on Merli's ex GTS-t - the BOV was positioned on the plenum side of the cooler - mine is on the turbo side.......

[Merli]

This sounds like a classic case of atmo-venting BOV still cracked open causing the car to stall on rapid decelleration...

You're going along nicely at 4000rpm, light up ahead goes red. You quickly release the throttle, shutting the throttle butterfly and causing the BOV to vent. But the BOV isn't wound tight enough and is still a little bit open as the car decellerates. You hit 3000rpm, 2000rpm, 1000rpm. Your BOV is still a little bit open and leaking all that air out. You engine senses that loss of air, can't keep revs up, and stalls.

Solution: Tighen BOV / Buy different BOV with much tighter spring (e.g. move from Bltz DD BOV to Trust Type-R) / Put on a recirculating BOV / Just make sure you don't let the revs drop too quickly and always keep the clutch engaged until about 1200rpm

[USRB25S13]

I have the same problem as you. But I still have the stock ECU and MAF. When I put my larger turbo on I couldn't use the stock intake piping so I put my HKS SSQ back on. I never had idle problems with the HKS and stock turbo.

I found with the larger turbo it stalls out if I let the revs drop too fast. It's a real PITA! I noticed my A/F ratio goes to 10:1 when the RPM's are droping down. I think the stalling problem has to do with there being much less volume of Air between the MAF and Turbo.

[KamikazeR33]

hey bman mine dies if u like floor it in first gear all the way to redline then just suddenly put the clutch in - i have a microtech - cams arent in yet and i dont have a bov on at all

i still have to get mine 100% tuned as its only on a road tune atm

i do have a custom plenum and xf throttle body with 200sx tps sensors with correct voltage

anyone got any ideas?

[B-Man]

I'm fairly sure mine is the BOV - it's a turbosmart supersonic plumbed back to the air filter. - I'll try unplumbing it first. Then I might remove it just for a test.

I think the trick might be to reposition the BOV as far away from the AFM as possible.

Kamikaze - It sounds like yours is a tuning problem. BTW - the Ford Explorer TPS works with the Microtech and the PFC too.

[B-Man]

Well - I just tried the BOV setting on hard / soft - no difference.

I took the BOV off completely and checked it for leaks and bad o-rings - but it all looks good.

I blocked the BOV flange whilst it was off - and same problem - but I sort of expected that - as there would be a fiar amount of reversion from the 3040 - which would affect the AFM.

I reckon I need to change BOVs or re-position it to the other side of the cooler.

Or even get one of those EIDS thingys.... is there a Non HKS branded one of these that is less expensive ??

So the Trust Type R BOV is a good one hey - how much are these ?? /me runs off to search the web.....

Fundage is a bit low ATM.....

Cheers,

Any other suggestions welcome.

[KamikazeR33]

the std bov is on the plenum side of the cooler... dunno how much difference it would make....

[B-Man]

Yeah - that's what I mean - mine is not on the plenum side right now. (I have Greddy front facing plenum so non-atmo plumbing is a bit hard)

By changing it to the plenum side I'm sort of hypothesising that there will be more volume so that reversion won't be so much of a problem -

[T0nyGTSt]

If this all goes to pot, PM me and I'll see if one of the workshops has a spare EIDS Pro lying around.

T.

[B-Man]

Thanks Tony - UAS reckon that they can tune it out -

I've been reading the "this low rmp idle problem" thread - or whatever it is called - and 'the phantom' reckons that a thing called a dashpot is the go

From what I understand - it attaches to the TB - and lets the butterfly open quickly, but close slowly - which fixes the reversion problem ..

I'll see how I go with the tune -

then maybe look into the EIDS or Dashpot thing

Cheers,

[Roy]

oooh, havent read that thread or know how the dashpot works, but be careful when putting things on throttle bodies that change how they open / close, throttle jammed wide open or something to cause you to carry trailing throttle when trying to brake could be scary.... :Oops:

[Steve]

A couple of things to look at if you havent already,

Have you still got the mesh on the AFM?

Check your fuel cut recovery rpm on the power fc - should be around 1200rpm - go into settings then idle - under your redline setting is the fuel cut recovery rpm for ac on and ac off.

Also, have you tried winding your AAC valve open a couple of turns?

Hope it helps

[B-Man]

Hey Steve -

Yes the mesh is still there.

I'll check the fuel cut setting - from memory it was 1100.

Is the AAC valve the idle control screw on the plenum ?? If so - yeap, I've tried everything......