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NeilH

Aux Air Regulator and Poor Fast Idle - Is This Correct?

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Hi all

 

Almost totally cracked previous cold start issue (10+ cranks needed!) on '81 Euro SC 3.0ltr. New cold start valve\injector seems to have cured (with the last 2-tests at least) as the old one only gave a thin stream spray pattern!

However, now the cold fast idle speed is playing up - whereas before doing all this work it was perfect;  

- Initially fires from cold but holds at 900rpm

- If I blip throttle couple of times, jumps to appx 1,600rpm

- After 90-120 seconds still 1,600rpm

- Couple of blips of throttle again, drops to something like 1,100-1,200 then lowers to 900rpm

- Have checked Aux Air Regulator - continuity, voltage and operation on bench all good - though is the attached image correct for it's "cold" open throttle?

- With voltage applied, slowly closes over 2-minutes or so. If I then blow trough it I hear a tiny "pop" as it closes to all airflow - I suspect the disk somehow moves with the air flow to finally seal closed?

- I'm unable to apply air flow through it during the warm up process on a bench and wonder if it might perform differently - wondering if "blipping" the throttle is having an effect?

 

There is also the Aux Air Valve (hidden on rear of engine) but I don't know how that operates or can be tested. I've not removed the engine for any of this

Does the attach "cold" aperture look wide-enough?

The disc inside seems to move freely if i put a screwdriver through the aperture and move it wider open - against what appears to be a spring action - that returns it back to the same cold aperture size.

 

The work done = replaced CSV, cleaned WUR filter (all WUR pressures OK) and fit new fuel filter.

Thanks for nay help to get this final little issue sorted so all 100%

 

 

Best regards

Neil

          

AuxAirRegColdOpen.jpg

AuxAirRegWarm-Closed.jpg

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Replied on your other thread without realising you’d posted this.

Am not sure the symptoms you’re describing are anything other than normal, or more accurately: anything other than what I typically find with mine at the ambient temps we have at this time of the year in the UK.

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The AAV looks fine - they don’t open fully. 
 

My SC idles only slightly faster when cold (maybe 1100 RPM) then drops to normal 900 ish after a few minutes.   1600 isn’t normal. 
 

When warming up it’s a bit more prone to ‘kangarooing’ in gear at slow speeds but normal after a minute or so.  
 

When my airbox was cracked it used to have unpredictable high idle issue when cold.  
 

Take the air filter off and check the screws next to the plastic ribs.  If they are loose and can’t be tightened, your air box is cracked.

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