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(Post Link) post #1 of 29 Old 07-04-09 Thread Starter
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Silicone Hosing = Poor/Lumpy Idle

sorry if mods think this is more of a techy topic, wasnt 100% sure which it should go in.

i tried fitting silicone hosing to my 156 2.0 today, between the MAF and throttle body, along with an external mini-k&n style oil breather.

im sure there are no air leaks, as everything is "on" properly, and all clips tightened right up, checked with "fairy liquid test" too, but it idles lumpy as hell, and goes to quite low RPM. drives alright though.

i tried an ECU/throttle rest, with no luck.

i put the old intake pipe back on between MAF and throttle body, and refitted the oil breather, and its 100% fine.

why might it misbehave like this?

does it "need" the oil breather, even though i read it should run cleaner without oily air going in?

My 156 GTA with Wizrdovoz system Video 1 Video 2
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Re: Silicone Hosing = Poor/Lumpy Idle

Where's the idle stabilisation system?
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(Post Link) post #3 of 29 Old 07-04-09 Thread Starter
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Re: Silicone Hosing = Poor/Lumpy Idle

the what?

i have no idea what that is, or where it is.
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Re: Silicone Hosing = Poor/Lumpy Idle

If all you're doing is replacing an air intake hose (ignore the oil breather, it doesn't affect the air intake side and it is only effective at low speed anyway) then there is a leak somewhere in the hose.

Listen for a sucking or a slight hissing noise to try and identify where it is.

If nothing is apparent, try a TB reset and then go for a good hard drive - it could just need to learn the newer, possibly higher intake values.
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Re: Silicone Hosing = Poor/Lumpy Idle

cheers for that. the only audible noise was coming from the oil breather, and i did check for leaks, couldnt find one, did also try a reset.

it drove ok, but was lumpy at idle, and had a very low idle.

will give it another shot tomorrow, not hard, just the hose between MAf and t/b.
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Re: Silicone Hosing = Poor/Lumpy Idle

I did a similar thing with my V6, removed the resonance box and replaced with a couple of sections of silicone hosing and some joiners. Had to bypass the oil breather like you did with a small breather filter. I've had no ill-effects, other than the odd occasion when my silicone hose pops off the TB due to the awkward angle that the 166 TB is at.
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Re: Silicone Hosing = Poor/Lumpy Idle

I don't have 156 2.0 so I'm guesing but is the breather pipe conected somwhere else than rocker cover? It is sounds for me like leak somwhere in inlet. Try to block the breather pipe where you put small filter (for the test only). Then you will know.
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Re: Silicone Hosing = Poor/Lumpy Idle

interested to hear how this pans out

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Re: Silicone Hosing = Poor/Lumpy Idle

if it is something to do with the breather then you can buy adaptor thingys that cut thru the silicone hose and leave a metal conector in place allowing you to reattach the breather hose as it originally was.
Sorry if that doesn't make much sense I know what I mean!
But more to the point, I can't see why the breather would make any difference as it is not any kind of vacuum and is just there to stop pollution from the crank breather (i think!)
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Re: Silicone Hosing = Poor/Lumpy Idle

Quote:
Originally Posted by aziraphale View Post
sorry if mods think this is more of a techy topic, wasnt 100% sure which it should go in.

i tried fitting silicone hosing to my 156 2.0 today, between the MAF and throttle body, along with an external mini-k&n style oil breather.

im sure there are no air leaks, as everything is "on" properly, and all clips tightened right up, checked with "fairy liquid test" too, but it idles lumpy as hell, and goes to quite low RPM. drives alright though.

i tried an ECU/throttle rest, with no luck.

i put the old intake pipe back on between MAF and throttle body, and refitted the oil breather, and its 100% fine.

why might it misbehave like this?

does it "need" the oil breather, even though i read it should run cleaner without oily air going in?
I assume you closed off the oil breather vacuum connection on the throttlebody side, if it still exists of course with the new intake pipe...
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(Post Link) post #11 of 29 Old 08-04-09 Thread Starter
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Re: Silicone Hosing = Poor/Lumpy Idle

jwq, what vacuum connection is this?

forgive me for sounding dumb, but the only thing breather-related that i can see is the actual breather hose...
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Re: Silicone Hosing = Poor/Lumpy Idle

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Originally Posted by aziraphale View Post
jwq, what vacuum connection is this?

forgive me for sounding dumb, but the only thing breather-related that i can see is the actual breather hose...
There should be an (oil breather) hose going from the top of the crankcase to the intake... That's the whole idea... The overpressure/oil fumes get sucked or blown out of the crankcase, and fed into the inlet to get burned....
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Re: Silicone Hosing = Poor/Lumpy Idle

thats what i have removed, which is why i asked if it was "needed" if some people have said it is a bad thing(or not necessarily good) for the engine.
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Re: Silicone Hosing = Poor/Lumpy Idle

The oil breather will not be related to the problem. It allows air pressure build up in the crankcases (from the pistons going up and down) to vent somewhere.

They connect it onto the inlet as that means any oily fumes in there will be burnt rather than ejected into the atmosphere. The engine would prefer not to have to burn that stuff so in theory it should run better without the crankcase vent attached to the inlet.

I think the beast just needs to adapt to the new inlet-side mods. Try driving it a bit and see if the ECU adapts.

The crank-case vent needs to just go somewhere where it won't dribble oily condensation stuff over your engine.


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Re: Silicone Hosing = Poor/Lumpy Idle

Quote:
Originally Posted by Ralf S. View Post
The oil breather will not be related to the problem. It allows air pressure build up in the crankcases (from the pistons going up and down) to vent somewhere.

They connect it onto the inlet as that means any oily fumes in there will be burnt rather than ejected into the atmosphere. The engine would prefer not to have to burn that stuff so in theory it should run better without the crankcase vent attached to the inlet.

I think the beast just needs to adapt to the new inlet-side mods. Try driving it a bit and see if the ECU adapts.

The crank-case vent needs to just go somewhere where it won't dribble oily condensation stuff over your engine.


Ralf S.
That's all obvious of course , but my point was that I don't know what part of the inlet is replaced by the new sillicone hosing...
If the place where the oil breather hose was connected to the inlet is now open, it would of course suck unmonitored air through there, causing the bad idle etc....
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(Post Link) post #16 of 29 Old 09-04-09 Thread Starter
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Re: Silicone Hosing = Poor/Lumpy Idle

hi, no, the pipe where the breather hose went is not left open..im not that daft :P

i will get a photo of how it is now, how it look with the silicone hosing on, and then maybe take it for a blast.
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Re: Silicone Hosing = Poor/Lumpy Idle

I'd be inclined to think the cause of your lumpy idle is more to do with the throttle body position which you may have inadvertantly touched while changing the intake hose, rather than an air leak - especially as you mention that it drives OK.

Have you done the full TB reset procedure?
  • Remove battery leads from the terminals and touch together.
  • Reattach battery leads to battery.
  • Turn key to MAR (all dashboard lights on) but do not start.
  • Leave for 90 seconds or so to allow TB to reset it's position.
  • Turn ignition off and leave for 90 seconds.
  • Fire up the engine without touching the accelerator pedal and leave to idle for at least 10 minutes.
  • Go for a drive and make sure you cover the full RPM range.

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Re: Silicone Hosing = Poor/Lumpy Idle

ah, i did that, the only thing i didnt do was let it idle for ten minutes.

if i had knocked the throttle butterfly, the lumpy idle would have stayed present even after i had changed back to the standard hose though, wouldnt it?
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Re: Silicone Hosing = Poor/Lumpy Idle

Possibly, yes! Doesn't hurt to try the full reset procedure again, though!
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(Post Link) post #20 of 29 Old 22-04-09 Thread Starter
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Re: Silicone Hosing = Poor/Lumpy Idle

ok, *finally* got round to sorting this, wont idle correctly due to the lack of oil breather, so the breather is back in. not quite optimal because the breather is slightly twisted/kinked, but theres no ill effect, took it for a good blast after resetting the throttle/ecu yesterday, goes very well.

couple of piccies, had to get a metal t-piece, as all silicone ones i can find have a 1" T inlet, no good for the alfa's breather, too big.
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Re: Silicone Hosing = Poor/Lumpy Idle

In the second picture is there a nasty kink in the hose as it goes into the engine???
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Re: Silicone Hosing = Poor/Lumpy Idle

the red silicone hose you mean? no, there isnt, its just the way the light has hit it, the "kink" on the inside bend is a shadow.
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Re: Silicone Hosing = Poor/Lumpy Idle

Looks good.
Have you got stainless manifolds on there as well?
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(Post Link) post #24 of 29 Old 22-04-09 Thread Starter
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Re: Silicone Hosing = Poor/Lumpy Idle

cheers.

yes, its a supersprint, although the flexi is failing yet again. "wizrdovoz" is making a custom one up for the 2.0 TS..
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Re: Silicone Hosing = Poor/Lumpy Idle

That looks stunning

How is the crankcase breather affecting the idle though
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