Help with sorting my idle out.

[PobodY]

Now before anyone starts with me, I have searched the threads - I'm not looking for you to give me the information all over again... I'm just having some trouble working out what I need to be doing.

Basically I've been trying to follow the sticky, but not in the same order. I'm trying to do the easiest stuff first.

The first thing I did was to spray random vacuum lines with throttle body cleaner. - This has had a limited effect and now sometimes the idle drops to ~1000, but mostly it's at ~1250 (from ~1900 when cold - I can watch it for the 3 minutes the IAR should be operating and see it drop).

Next thing was to follow Shaun's guide on how to set the TPS. - I thought I was onto a winner with this one because it was at ~0.1V and it took a bit of bashing to get it to 0.49V (and 4.32V when at WOT). I made it easier for myself by finding the grey connector in this picture and just sticking the multimeter probes into the back of it.

The resistances were all spot on, so I'm happy it's working as it should. Idle is still the same.

Because the throttle body cleaner seemed to have done something, I thought it's most likely I have a sticky AAC or FICD. This is where I'm stuck.

Firstly; is this my idle screw? It does have a hose on it like people describe, but it seems to be in the right place.

Here's a wider shot.

Seeing as I had the multimeter out, I thought I'd do a spot more of electrical checking. I was trying to follow the service manual instructions (here), but I'll be damned if I can find that harness!
Am I looking in the wrong spot? I assume that's a picure of the fuel filter, but this is what I've got:

No harness in sight! Where might it have gone to?

I've had a look at the throttle connection and the linkages; they look ok to me (i.e. not slack, but also not excessively tight). Maybe the stop is wrong, but that looks like a royal pain to fix (so I'm assuming I don't need to touch it).

What I need to do now is get under the mainfold/plenum to get access to the AAC and FICD. How do I do that?
Firstly I'd really like to get rid of that bracket that's in my way; can it be done with the engine in, and if so how (where) to I undo it).
I can't help but feel that I should be able to do this without taking the plenum off; the diagnostic procedure shows them just pinching the vacuum line whilst the engine is running... but I'll be damned if I can work out which line it is, let alone pinch it to see if the idle changes!
This makes it look like they should be hanging right behing the BOV, but I'm pretty sure they're bolted to the head or maybe the mainifold it's self.

I haven't checked the lambda sensor yet. I can't say that I've checked every vacuum line for perishing, but as you can see I've replaced quite a few of them on the off-chance.

Anyway, hopefully I won't get too badly flamed for this.

 

[pulsarboby]

george! in that second picture down, the idle speed control screw is sitting in between both those pipes around an inch below (not inside the pipe which is the main throttle body vacuum)

now before you do anything else....spray that screw with some wd40 and try adjust the idle speed through that.

 

[PobodY]

Thanks - I'll go and do that now! - I thought it might be, but I keep reading about this bit of pipe you need to follow to find it.
It does look like someone has messed with it before because that white paint has gone.

 

[pulsarboby]

yeah not all have the short bit of pipe on them (its only a guide for your screwdriver, nothing more)

 

[PobodY]

I've had a bash; which way should it go?
It was screwed all the way in (i.e. no more turns clockwise), and unscrewing it seems to bring the revs up... although it's a little hard to tell because if I 'blip' the throttle it goes up then slowly comes back down again.

It has also started to give me white smoke since I started messing with it - I don't think it's oil (it doesn't smell like it), but I'm a little surprised that it's condensation given that I'm warming the car up. It's definitely wet in the exhaust not oily - maybe it's just getting up to temperature and driving water out of the muffler? I'm not going to stress about it now - I'm reasonably confident that I don't have any coolant leaks (I've never lost coolant before), so I'm not going to stress about it (much).

 

[pulsarboby]

im 95% certain that screwing it in lowers the rpm but not positive. trial and error on that one!

 

[PobodY]

I think so too - makes sense that if you screw it in it closes (meaning less air flow and a lower idle).
Bugger - phase two then.

 

[vss irvine]

have you tried re-earthing your maf?

ive had success lowering the idle speed with this mod

there should be a 'HOW TO' somewhere?

here

http://www.gtiroc.com/forums/showthread.php?t=31752

 

[PobodY]

I haven't, but as I said; I've got the mutlimeter out, and I can easily reach the MAF.
I'll do that now.

EDIT: I think the MAF is ok, but to be honest the reading on my multimeter jumps around a bit at that level (and seems to generate a reading without my closing the circuit with an earth) :shock:
I might have a bash at re-earthing it at a later date anyway - it's a relatively simple job (I just don't have any appropriate wire at the moment; it's all dual or triple core 10A), and it can't hurt to just run an earth back to the battery.

I've been thinking, and I'm pretty sure that it must be something sticking in the AAC (or related) because the idle does drop (just not predictably or routinely), which suggests that it is something that comes and goes.

Shaun also suggested the engine coolant sensor, and I guess if that had something loose in it it would have the same effect; brake really hard for example and the connection is restored, but move the car again and it goes.

 

[PobodY]

Just out of interest, does the idle screw come all the way out?
Maybe I can unscrew it, and add a belt of the spray directly into the valve; that way I wouldn't have to dismantle everything.

I'm a little concerned that I've made it worse now. I drove to the shops and the idle was at ~1900 the whole time (i.e. it didn't drop at all).

 

[Shaun]

George,iirc before altering the idle with the screw you need to unplug the TPS and then reconnect it after its been altered otherwise the screw alone doesnt alter the idle.

 

[PobodY]

Well fuk me that's some good advice!
No wonder it didn't seem to make any difference - right that'll be tomorrow's job!

 

[GTIR-LOZ]

yes the screw comes right out it has a rubber o-ring on it

if you have been spraying cleaner around and the idle changes then you have an air leak so you need to sort this out before going any further

 

[PobodY]

I don't think it's a leak in the PCV piping because I changed all of that... plus the hoses to the boost controller and wastegate...
I haven't changed any of the hoses behind (under) the manifold because I can't get at them.
What about the diaphragm in the BOV? Is that likely to spring a leak and cause an erratic idle? - I think it's a bailey.

For the most part the spray does nothing, but if I've been driving for ~30 minutes and stop at the lights the idle goes down to ~1000. However, if I drive forward and stop again (because the lights change, but I don't get through) it will go back up to ~1500... then creep back down to ~1200.
That's why I think it's something sticking.

Anyway, I have silicone grease to put on O-rings and such like for when I take valves apart... Sometimes that's all it takes; a bit of a recondition on the seals (perhaps not in this case, I haven't tried yet).

 

[geetee]

George,iirc before altering the idle with the screw you need to unplug the TPS and then reconnect it after its been altered otherwise the screw alone doesnt alter the idle.

Quite right. Disconnect it and blip the throttle over a certain rpm (1500?) a few times before adjusting the screw if I remember correctly.


*EDIT* - Which Bailey BOV is it? I used to have a single piston one on mine that was letting past at idle, swapped it for a Forge jobby resulting in a much more stable (but still a little high) idle.

 

[GTIR-LOZ]

the bailey needs to be a twin piston type otherwise it can leak also i found mine idles high due to either worn or incorrectly adjusted throttle end stops there are two, one below each linkage best way to check is push down on the throttle arm where the cable is if the idle lowers then these need adjusting unscrew the stops then lengthen the rods until there is no more movement downwards of the arm that is directly connected to the throttle plates then rescrew up the stops, i did mine just until they touched the arms then tighten everything up and retry - it worked for me i think also you can get a bit of build up around the throttle plates which causes them to stick off their bottom position and cause excess air to get through you need to remove the lid and clean this area

 

[pulsarboby]

these idle probs are a real pain to try & fix, sometimes its a process of elimination, but the other thing it could also likely be is the tps itself.
it is after all just a variable resistor and it may not be reading correctly at lower range.
try connecting up your ohms meter and manually open / close the throttle and see if the readings change as they should.

thats assuming that what shaun has suggested doesnt work! i must admitt i never knew that, ive always adjusted the idle screw to set base idle without disconnecting tps, so ive learnt something new here myself.

 

[PobodY]

The first thing I did was the TPS - it was at 0.1V, but I've adjusted it to 0.49V (and 4.32V at WOT).
Hasn't made any difference to the idle, but maybe the mixture is better at idle now - I guess I'll find out at MOT time!

To be honest with you, if I hadn't got the week off work (and got bored sitting around the house) I would have just kept ignoring the idle... I just thought that I had some spare time, and that I might get somewhere if I tried a few different things.
After this week, I'll probably go back to ignoring it again until the time I decided to take the plenum cover or manifold off... then I'll start again.

 

[pulsarboby]

but your only checking ohms at idle and wot!
try it through the range, as you gradually open the throttle (especially first 5mm) watch the readings on meter to make sure they are smooth and rise progressively and dont jump suddenly, if so this could indicate dirty resistor contact in the tps itself which in theory could be partially sticking now and again.

 

[PobodY]

I've taken the idle screw out, and it looks like this:

Lots of black gunk on the end of it; so out with the throttle body cleaner! I've sprayed into the body as best I can, and I've coated the O-ring with some silicone grease (although to be honest it's not in bad shape).

I also took the BOV off: Is this normal?

Looks like it was either the wrong BOV or it didn't have the right fitting kit... anyway, I took it apart:

It's only a single piston and spring - I've cleaned it up. The O-ring has definitely been nicked at some point, and shows wear, but it hasn't split. Plenty of silicone grease on that, and back together again.

Whilst I'm at it, I've sprayed lots of cleaner into the plenum too.

I'll check the TPS again - I see what you mean; it's one thing to say it's at 2kOhm, then less than 11kOhm, then more than 11kOhm, but that doesn't mean it's a nice linear response.
I'm not sure that throttle body cleaner is the right spray for that one - maybe I need contact cleaner! :twisted:

I guess I'd better put it all back in the car now.