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Sorry To Ask, Another Idle Problem!!


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#16 Foc'd off

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Posted 06 April 2013 - 08:47 PM

Let's not get into an argument over this. All I really want to know is why my IACV is holding open at any temp or rev setting.

 

My bets is a damaged ECU/PCM module but I would still appreciate any feedback on this!



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#17 artscot79

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Posted 06 April 2013 - 08:56 PM

Simply put from experience try another icv at 80k its well past the usual change interval its cheaper and simpler than messing with ecu pcm if the icv does not cure the issue then its common to have a faulty throttle body the ecu pcm being expensive to repair would be my last port of call if the icv is faulty it will stick open normally we just swap it with a working one to check takes 5 mins to do i am being genuinely honest not trying to argue all idle issues ive had either the same or similar to youres was resolved with a new icv including my own old mk1
Pcm faults with youre issue are so rare without other symptoms

#18 wase16ll

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Posted 06 April 2013 - 09:04 PM

no arguments here...all about info and opinions
think what your missing arts, is IAC is being held wide open, have never come across this myself but in order for it to do that it has to be supplied a constant 5v...[maybe 12, cant remember] which indicates a wiring short or more likely a pcm problem...
pcm/ecu's are common problems to those in the trade...have sent two away for repair already this year.

its possible the short is within the IAC, which should easily be eliminated with a resistence test...
in all the years, i have only ever changed a handful of IAC'S over a multitude of makes, often the problem is just cleaning, some its cheaper to change, others its cheaper to clean...

#19 artscot79

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Posted 06 April 2013 - 09:13 PM

Im not in the trade anymore but have changed a fair amont of icv valves collapsed hoses and pcv valves why its so common on tge focus compared to others i have no idea ive never come across the pcm causing the issue im not saying it isnt the case but if i was hinging my bets it would be the icv or the wiring plug to the icv which can suffer from corrosion or get brittle from the heat ive always found on the fords with these types of issues they are never as simple as other makes sadly the ford icv never responds to cleaning myself and many others who had the mk1 all had to replace it at around 50-60k due to similar issues

#20 wase16ll

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Posted 06 April 2013 - 09:26 PM

would agree with a lot of that, just the fact its fully open on connection, closed at disconnection, so not sticking, that indicates to me a signal problem, add to the mix info about pcm accident damage, increasingly looks like the brain or associated wiring/connections....but could equally be something else is fooling the ecu into believing engine needs more air to idle...

my money is on pcm related....but diagnosing over net is nigh on impossible

but hey...if it was easy, id be scratching for work :)

#21 artscot79

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Posted 06 April 2013 - 09:44 PM

Its an unusual one i dont deny it ide still be tempted to pop a scrap one in to see what happens

#22 Foc'd off

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Posted 07 April 2013 - 10:08 AM

iac isnt the easiest to test without an oscilloscope..
you can do a basic resistence/supply test of iac

disconnect wiring, test at iac

should have approx 9.5 ohms between terminals 1 and 2

disconnect wiring, ignition on, test at harness plug

11-14 volts between terminal 1 and earth
 

 

 

I'll go out and check these now and report back, I'll also be taking a more thorough look at the condition of the wiring for frayed/earthing wires corrosion etc.

 

Thanks all for your comments!



#23 Foc'd off

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Posted 07 April 2013 - 01:56 PM

Well I'm no nearer to a solution than before.

 

First I measured the IACV, that comes back as 9.7 ohms, the plug on the loom shows one pin at 12.8v and the other appears to be earth. I was wondering why bother to have an earth wire to the IACV when it could easily be done through the chassis ground?

 

Anyway, I removed the ECU and stripped it to find masses of metal filings inside, some were on the legs of a rather large processor looking chip. I removed all the dust etc and rebuilt it. Still no difference, the IACV holds fully open no matter what.

 

Whilst I'm thinking about this, does anyone know the travel of the IACV piston? Mine only moves about 3mm from shut to fully open!



#24 artscot79

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Posted 07 April 2013 - 05:55 PM

from memory and it was a while ago it was around 4mm

 

you may need to replace or have the ecu rebuilt i know bba reman state the diodes have a habit of failing but again this will cost money this may be one of those issues that just goes on and on



#25 wase16ll

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Posted 07 April 2013 - 08:30 PM

First I measured the IACV, that comes back as 9.7 ohms, the plug on the loom shows one pin at 12.8v and the other appears to be earth. I was wondering why bother to have an earth wire to the IACV when it could easily be done through the chassis ground?

should have green/yellow wire [supply] and black/yellow wire [signal]
it could be with engine off, this signal wire is earthed through the pcm, be interesting to know if you still get earth with engine running, if so, then think your almost definitly getting a short in pcm/wiring.

as said before, that wire should be averaging a 3 volt switching signal, maybe worth checking if your getting an earth with IAC both connected/disconnected whilst running.

not forgetting that signal would be too fast for voltmeter to handle, but if its earthed then should show up

#26 soulman123

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Posted 10 April 2013 - 03:35 PM

Let me enlighten you.

 

PCM = Power Control Module

TPS = Throttle Position Sensor

TMAP = Thermal Manifold Absolute Pressure Sensor

PCV = Positive Crankcase Ventilation

ECU = Electronic Control Unit

IACV = Idle Air Control Valve

 

I thoug

 

Btw Thanks for taking the time lol 

 

Ditto, I was lost too lol



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