35 replies to this topic

[NQRSoobee]

My Gen2 RX has seen better days but it still rolls along getting me to work.

 

I managed to pull the IACV, on advice that it would be dirty, to give it a clean as it's usually the culprit for a persistant uneven idle normally showing up as an O2 code CEL.  So I dug in, removing various ancillary gear to access the IACV mounting bolts.  Removed the three mounting bolts (see attached photo showing only 3 mounting holes on the inlet manifold) and to my amazement the IACV looked quite clean plus it was easy to move the mechanism which was also smooth in movement.  As I had the IACV off the inlet manifold so I ran it through my small Ultra-sonic bath, gave it a good wipe, dried it in the sun for more than an hour then Inox'd it thoroughly.  After the clean & lube the IACV moved very freely & smoothly so I re-installed the IACV using a new gasket plus a little gasket goo (markings from the old gasket appear to show it not quite fully sealing which had me thinking a slight vacuum leak).

 

Outcome from the work is no change in behaviour.  The behaviour is:

1.  the engine still doesn't idle smoothly;

2.  the engine holds on a number of hundred extra revs when the A/c compressor is engaged (when the compressor cycles off the revs immediately drop away);

3.  when warming up as the revs slowly drop until it hits around 1300 to 1400 rpm where upon it jumps up to 1800 rpm (I usually let it warm up a bit so this behaviour doesn't affect the car while I'm driving it).  The controller on sensing this compensates quite quickly dropping the revs back to around 1300 rpm;

4.  when I release the brake pedal the revs will pick up a few hundred rpm then immediately drop back (I've seen this behaviour on many other cars but not all, so am unsure what if this is normal for a Subaru);

5.  always smells like it's running rich; and

6.  in cold weather only, the CEL will light up, when I check it it's a Code 32 (with the warmer weather finally here I don't get a CEL).

 

Given the above information it suggests that something else is causing the issue.  No @#&% Sherlock!  :-)  Which means I'm now a bit baffled as I've done the usual fixes and nothing has cured the issue.  I'm still thinking with the rich running that it may have a vacuum leak somewhere (I've checked the clamps are tight around the airbox etc).  Is there anything else I should inspect/clean in an attempt to get it to run nicely? (Short of checking the torque of the inlet manifold bolts).

 

Ta muchly.

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[duncanm]

does brake response point to an electrical issue? Volts dropping when the brake lights are on?  Do you get the same behaviour if you turn on the headlights?

 

If so - maybe clean up the block and chassis grounds around the engine bay

[El_Freddo]

Remove the vac line to the brake booster and block it. Do a test warm up but not a run down the street unless you're confident that you can push a brick through the floor to pull it up without the power assisted brakes.

You might find there's something wrong with the brake booster line or the brake booster itself.

How many k's has it done, and does it use any oil?

What oil type/viscosity are you running?

Cheers

Bennie
Ps - as for your AC, low on gas or running hichill (awesome stuff, I love it)?

[NQRSoobee]

Cheers peeps.  Lots of ideas to help, now I need a fine weekend to get into it.

 

Duncanm:

Hadn't thought of that 1.  Be worth me giving the ground points the once over.

 

El_Freddo:

Good idea to check if the power booster is leaking air.  Added info: The booster does keep vacuum overnight but only has 1 or 2 pumps in it before it's brick pushing time.  To me that suggests if there is a leak then it'd be the vacuum line rather than the brake booster.

 

Kms wise it's coming up on 250k kms but I reckon it's had quite a hard life before I got it.  Clutch is identified in the servicing book as being replaced at, I think, around 215k km but it can shudder badly on take-off yet doesn't slip.  When fully engaged the clutch makes a jittering noise that isn't a squeal.  The mechanic who does the regular servicing reckons it's the thrust bearing squeaking on the slide & very careful application of a few drops of thick oil applied through the clutch thrust arm portal can fix the noise.  I put up with the noise as oil next to a clutch plate isn't a good combination.

 

Yes, it uses a little engine oil but from what I can tell it doesn't burn it.  My mechanic tells me oil is very slightly seeping from around at least one of the cam seals.  I haven't taken the cam covers off to check conclusively but will have to soon as the cam belt is due next month (Sticker under the bonnet identifies it as a Gates belt and it's 6 years are up).  Barbbachello (Sp?) has advised me on a number of brands which are worth purchasing as a replacement.

 

Oil viscosity I dunno, I leave that to the fella I get to service it.  Yeah I know I should be getting into it more but... my driveway ain't flat (in fact it's got a reasonable slope on it), getting rid of old oil is always a pain & I'm over getting down on the cold concrete... so he puts in a French brand of oil which does the job.  (Given he's originally a Brit I find it a bit ironic but his apprentices always do well with one seriously knocking on the door of working in F1).

 

The A/c controls is one of those set & forget the temp automatic types with the green display that disappears on a sunny day.  Pumps out heaps of cold air when requested & cycles in/out regularly so my thinking is it's not the A/c itself but something that's part of the controlling system for the engine.

[duncanm]

.. re: the a/c - it is supposed to rev up when engaged.

[NQRSoobee]

Er... Tilt... I disagree.

 

Yes, a teeny bit more air is meant to be let in when compressor cuts in which the ECU compensates by increasing the fuel supply which in turn compensates for the extra load of the compressor.  The intent is for the engine idle speed to be maintained neither higher or lower than idle whether the A/c compressor is engaged or not.  Otherwise, cars that have automatic transmissions would on revving up and push harder against the brakes; if a driver was using light application of brakes then a self revving up car could roll hitting an object (Eg another car in peak hour traffic)... I'm sure a manufacturer would last about 5 seconds in court with that argument.

 

My Soobee, when the compressor cuts in, hunts from between 700 to 1400 rpm while the compressor is activated then when the compressor is de-energised it will settle down to around normal idle but still slowly hunt in the 700 to 900 rpm range.  The engine does this whether I have a CEL, Code 32, or not indicated on the dash.  The fact that it did this exact behaviour today while in peak hour traffic only confirms the issue I'm seeing but I can't quite diagnose what is the root cause.

[El_Freddo]

Ps - as for your AC, low on gas or running hichill (awesome stuff, I love it)?

 

Have you confirmed what gas is run in your system yet?  It *should* be listed on the sticker under the bonnet.

 

You might find that if it is running hichill that the revs will increase more than they should as this stuff operates at lower pressure than that r134a stuff.  This could mess with the ECU's programming... maybe.

 

The other thing I can think of is that the IACV could be electrically faulty - meaning it won't be doing it's job properly.  Any chance you might be able to swap it out with a known good unit?  Or bench test the resistance of your IACV unit?

 

Cheers

Bennie

[duncanm]

Gen3 says (idle speed):

 

Unloaded. (With headlights, heater fan, rear defroster, radiator fan, air conditioning, etc. OFF)
Idle speed [No load and gears in neutral (MT ve-hicles), or N or P (AT vehicles) position]:

650 ± 100 rpm

 

Loaded. (Turn the air conditioning switch to “ON” and operate the com-
pressor for at least 1 minute before measurement.)
Idle speed [A/C “ON”, no load and gears in neu-tral (MT vehicles) or N or P (AT vehicles) posi-tion]:

850 ± 100 rpm

 

but yes - 700-1400 is excessive.

[NQRSoobee]

Duncanm:  Oh wow, that's a bit unfortunate with the idle revs pushing up & down with the A/c kicking in/out.  I'm a bit surprised to be honest because my personal opinion is it'd last about 5 seconds in a court if used as evidence for a car running away under brakes while light brake pressure is applied.  Good info thanks & I've still to give the ground points a once over.

 

Bennie:  I had a quick look under the bonnet today (after work as they have a nice flat car park so was doing the weekly check of fluid levels) and there's no obvious sticker that I can see advising what refrigerant is being used in the A/c.  I suspect it'd be something like R134a or similar but I'll have a closer inspection around the compressor most likely this coming weekend.

 

I don't have a spare IACV lying around, best I can do is drag out my multimeter and do a few basic checks on it; Eg. DC resistance, V to various connectors with ignition on engine not running.  That also means I'll need some base values to compare against?

 

Once I arrived home tonight I did an unusual test where I pumped the brake pedal to see what would happen with the engine revs (warmer day so no CEL, Code 32, for the trip home).  I expected with air being bleed into the system via pumping the brake pedal the engine revs to rise and they did to around 1400 rpm while pumping the brake pedal then as soon as I stopped the revs settled back down to around 700.  Seems like it's behaving as per normal to me so I'm still stumped what the root cause is.

[El_Freddo]

Once I arrived home tonight I did an unusual test where I pumped the brake pedal to see what would happen with the engine revs (warmer day so no CEL, Code 32, for the trip home).  I expected with air being bleed into the system via pumping the brake pedal the engine revs to rise and they did to around 1400 rpm while pumping the brake pedal then as soon as I stopped the revs settled back down to around 700.  Seems like it's behaving as per normal to me so I'm still stumped what the root cause is.

NQR - that doesn't seem right!

Pumping the brake pedal should not make engine revs fluctuate!

I'd be disconnecting the brake booster, plugging the vac line into the engine and repeating the test. Engine revs simply should not move with use of the brake pedal!!!

This steers me back to the thought of the brake booster being at fault. Or a very dodgy IACV... I know which would be easier to swap!

Cheers

Bennie

[NQRSoobee]

Well I was pumping the pedal often at about 2 Hz which is reasonably fast.  That will inject a fair amount of extra air into the intake manifold.  I might just try the same trick on my other brand car & see what it does.  Good thought though, the ECU should compensate for the extra air by closing down the IACV to hold revs.  Must've been remembering my Carbie days (which included things like a dual throat progressive down draught Weber on a 1.6 litre V-Dub playing with emulsion tubes, jets & air bleeds was... fun).

[El_Freddo]

The brake booster shouldn't inject any air into the engine. The engine is there to provide vacuum, not suck on huge amounts of air that play with the idle speed!

Something is really amiss here!

Reply #9 and 10:
https://www.sl113.or...p?topic=20553.0

And the last one too.

Cheers

Bennie

[El_Freddo]

Any update on this?  I was thinking about it today.

 

Cheers

Bennie

[NQRSoobee]

Thanks for checking in Bennie. Sorry been in hospital lately & still healing so no. I did wonder if I warm up my Soobee then give all the vacuum hoses a good waggle. That will at least show up if a vacuum hose is cracked or broken because engine revs should change, & I may hear a hiss, for the hoses that have issues. When I did have the bonnet lifted I couldn't see a plaque anyway obvious identifying which A/c gas it's running. Kinda suggests it's still the factory fill to me.

[El_Freddo]

That doesn't sound good mate.  My only excuse for not looking at my black smoke on start up in the EJ'd L series is hectic work load with exams and transitions....

 

Hope you're on the mend soon enough and get back doing what you love doing - and sort out that issue with the idle.

 

Cheers

Bennie

[NQRSoobee]

Okay; I had a go & removed the brake booster vacuum line, blocked off the inlet manifold nipple & then started up the engine. The engine started up fine to initially settle on ~1400 rpm then slowly dropped to idle on warming up.

 

Idle once warm still varied between 650 to 850 rpm indicated but it per usual it slowly hunts over about 5 seconds. I also tried running the A/c and it was much more controlled with revs hunting up to ~1k max then dropping to low idle of ~650. I'm starting to lean towards a defective IACV but that's an expensive bridge I don't wanna take without conclusive evidence.

 

Thanks for the link although reply 9 makes absolute no logical sense. Plugging the vacuum line completely disconnects the brake booster from the inlet manifold so pressing the brake pedal should not have any affect on engine idle speed what so ever by being disconnected. What would it achieve by pressing the brake pedal without vacuum; what else does it check?

 

Thankyou, healing okay but getting occasional dull aches in the area worked on.

 

Ah exams, I remember those. I've done a lot of Uni so relate far too well. Good luck Bennie, hope you street em.

[NQRSoobee]

Adding to my thread.

 

Well the old beast had its regular six monthly service last week and I was talking to my mechanic about how I'd pulled the IACV to clean it and found it clean. He suggested a clean of the throttle body (TB) which they found a bit of carbon in there & gave it a bit of a clean. So after the service on starting I was seeing 2.2 K rpm at startup & once warmed up around 1 K rpm idle. Not good for the engine on a cold startup with those kind of revs but good in that it meant that cleaning TB had a desirable effect.

 

So given he'd observed the throttle position sensor (TPS) had been played with by a previous owner and was fully at one end of it's adjustment it's a bit obvious a reset was needed to centralise it and find out what response the ECU would have to the new range of data especially since it's a 3 wire TPS. While in there I had a slight tinker of the IACV adjustment to:

1. Check it wasn't offset in it's mounting position so it wasn't binding, &

2. Give it a very slight adjustment more to a central position to again let the ECU deal with a more nominal range of data.

 

Both adjustments had a very beneficial effect:

1. Startup now from cold is now 1.5 K rpm max.

2. On warm up it settles down to a steady 700 rpm idle.

 

I still can't find any vacuum leak but:

1. Pumping the brake pedal still has the engine revs jumping up from idle to around 1200 rpm.

2. The engine still hunts when the A/c is on when idling but only from 700 to 1100 rpm.

 

Oh btw Bennie, found a sticker next to the condenser core. My Lib has R134A is in the A/c.

 

Next week is a new OHC belt as Gates recommend six years or 100,000 km and the six years is up. I've a full kit to go in but I'm told it may be not be the correct water pump as Subaru fitted three different types of water pump in the year of my Lib. Groan! New OE crank & cam seals to go in as well.

[CodeBurn3r]

havent read it all.. but ive seen this like 20+ times.. 
check your vac line on the drivers side fuel rail, it comes off the side of the fuel pressure reg... likely gone crispy and cracked..
it will do the same thing...

holds revs when AC is on, doesnt seem to drop down untill you tap the brakes.

let me know if this is it. 
everytime someone comes in here with the same issue, i write this, then never hear from the new user again...

[El_Freddo]

Well failing the brake booster check being the issue it means you don't need a new booster

Do what codeburner mentioned above. I've got my fingers crossed!!

Cheers

Bennie

[NQRSoobee]

CodeBurn:  Good thought, whom ever was previously trying to chase down the issue had already replaced that particular vacuum hose.  I'll check the hose & if needed replace it as I've got enough spare.

 

When I pulled the IACV another thin vacuum hose that ran near the IACV cracked badly so I've replaced that hose too.  Since then I noticed the fuel rail hose was slowly pulling itself off the inlet manifold so I fitted a clamp to make sure it stayed put.

 

Bennie:  That's very good news to read as I was kinda hoping I didn't have to hit the wreckers to find a working brake booster then have the "fun" job of replacing it.