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port matched 3l idle reset ????

art

CEG'er
Joined
May 9, 2004
Messages
119
Location
UK
OK maybe there wil be other views , but what i have been thinking about
our engines start off as 2.5l , and i researched how the factory idle is set
when the engine is fully warmed and under no load , the idle control valve is fully shut , the butterfly stop valve is adjusted on the tb to give the desired idle revs , and then sheared so it cannot be easily adjusted again , the desired revs are then programmed into the ecu , and using the idle control valve and other sensors, it tries to maintain those revs .
now with this set up from factory we then fit a 3 litre engine to our 2.5litre manifolds , and in theory the bigger engine should need an extra 25 percent more air to idle
it cant get it from the factory set up so pretty sure the idle valve and ecu are pretty over worked trying to maintain the set revs
so is my intention to fully warm the engine , get the idle valve in the closed position , and then unplug it , then screw a nyloc nut unto the butterfly stop screw and use it to adjust the butterfly opening to set around 650 revs , think that is around the factory setting , and see what kind of idle i can get
 
Hey Art; what size TB are you using ? If you have a 65mm, wouldn't that be correctly set for the 3.0L it came from ?


I have a 65mm on a 2.5L and have no idle issues at all ..... is your idle hi low or erratic ? .... .....G.
 
Well the idle rpm can be set by an XCAL when the car is tuned.

However I do not recall any idle issues when I was running my ported 3L on a stock SVT PCM. Many run un-tuned and I don't believe they have idle issues. If you do I would look elsewhere first.
 
For the most part, with modern ECU managed Ford engines, the throttle stop screw is not used to set the idle, rather, it is used to adjust the throttle stop so the throttle plate seals well in the bore without sticking. Ford idle strategies can be somewhat intolerant of leaks around the closed throttle plate, and this can result in inconsistent and hunting idle.

The hyper-active PCV systems on these engines leave a sludgy-sticky buildup on the intake manifold side of the throttle plate, which can cause idle hunting, and cause the throttle plate to stick closed, I have felt this with the first opening of the throttle by a little stick in the gas pedal.

The idle speed should be set in software, and the ISC valve should have plenty of dynamic range to maintain idle air bypass on a 3.0L engine.
 
yep from cold idles fine but revs quickly drop to 1000 instead of the normal around 1500
when it warms, revs are around 100 lower than they should be and wants to stall at idle many times , especially if the throttle is blipped
sure there is no vacumn leaks as I have checked every thing , swopped idle valve with the cougar I have so ruled that out
also swopped out crank and cam sensors , with no change , tps, sensor also
maybe will have to look at the maf sensor also
just another thing did the maf sensor change when the alloy body was replaced with a plastic one, I fitted a plastic one to my car but still retained the sensor from the original alloy body
 
Art; have you tried checking the water temperature sensors ?


One of the parameters the ECU uses to control start up idle speed is the coolant temp. ....G.
 
water temperature sensors were replaced when I did the 3l conversion around 3000 miles ago
 
Have you had the throttle body off lately? Any damage to the gasket?

Was the TB dis-assembled? Maybe the plate wasn't re-centered in the bore before the cross shaft screws were tightened.

Throttle shaft seal leak?

Any PCV deposits on the back of the throttle plate? Buildup here can keep the plate from closing completely, making leaks.
 
pretty sure there are no air leaks, if there was a slight leak would the lamba sensors not detect weakness and then try to richen up , think the problem is lack of fuel , have a fuel pressure gauge coming soon
 
I always thought the MAF sensor was calibrated to the housing. I didn't think you could swap the sensor from one housing to another without tuning it.
 
swopped the maf sensor with the cougar one , maybe a little improvement , but still stalls when warm, 20 times it will idle, then it will stall, and when it does, will stall immediately again when started, and again, and maybe after 15 mins will idle again, when starting from cold have noticed cold tickover is around 1000 revs instead of the usual 1500
carried out a vacumn check when warm and is showing 640 mb , that's a little over 9lbs vacumn
 
lots of measurement scales being quoted here.... thought this might help some of us guys compare them more easily .

i just checked my car and i'm reading 11 to 14 psi gauge below atmospheric pressure at idle....G.


CONVERSION CHART

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[FONT=arial, helvetica]Pa-psia[/FONT]
[FONT=arial, helvetica]In. Hg[/FONT]
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what would you need to adjust the maf transfer function
car was running 100 percent before the engine rebuild
only changes really are a bit more compression, ported head , and the svt cams swopped in place of the 3l cams
 
While I agree that the tune needs to be changed .... a ported 3L will run and idle just fine on a stock tune and injectors ... even for a non-SVT. I just caution changing anything in the tune before knowing for certain that its all running as it should be.
 
Hmmm. Interesting....:ponder: Mine dropped to about 14mmHg ever since i went the forged pistons route. Used to be around 18.

I have a stock 3L. I am guessing that you dropped the compression ratio when you rebuilt with forged internals?
 
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