XJ6 & XJ12 Series I, II & III 1968-1992

Adjusting the throttle butterfly to .002

 
  #1  
Old 11-23-2018, 05:59 PM
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Default Adjusting the throttle butterfly to .002

Hello all!

Hope you are all recovered from all that turkey and looking forward to eating the remains for another month!

Question.

How does one check that the throttle butterfly is set to the correct .002?? And what are the sides effects of it NOT being at 002?

Am i correct in thinking its the LEFT one that is set to .002?

Thank you!

Chris

 
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Old 11-23-2018, 07:47 PM
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Originally Posted by chrisleg View Post

How does one check that the throttle butterfly is set to the correct .002??

Remove ducting and elbow to the throttle body to expose the throttle blade.

Using rags, old toothbrush, and aerosol carb cleaner, remove all the black gunk in the throat of the throttle body....on both sides of the throttle blade.

When it's clean as a whistle use a feeler gauge at 12:00 o'clock between the throttle bore and the throttle blade. Adjustment is via an external screw, very much like the idle speed adjuster on an old fashioned carburetor. Loosen the lock nut and turn the screw so that a slight drag is felt against the .002" gauge. Might take a few tries to get the feel of it.

And what are the sides effects of it NOT being at 002?
Weird idle behavior, hesitation on opening the throttle. Cleaning the gunk is equally important as the adjustment, as the gunk alone case be a problem

Am i correct in thinking its the LEFT one that is set to .002?
Left one?

Not quite sure what you mean. Unless you have a v12 you have only one throttle body with a single throttle blade. The throttle body is attached to the intake manifold and has a cast aluminum elbow jutting out.

Cheers
DD
 
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  #3  
Old 11-23-2018, 08:18 PM
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Originally Posted by Doug View Post
Remove ducting and elbow to the throttle body to expose the throttle blade.

Using rags, old toothbrush, and aerosol carb cleaner, remove all the black gunk in the throat of the throttle body....on both sides of the throttle blade.

When it's clean as a whistle use a feeler gauge at 12:00 o'clock between the throttle bore and the throttle blade. Adjustment is via an external screw, very much like the idle speed adjuster on an old fashioned carburetor. Loosen the lock nut and turn the screw so that a slight drag is felt against the .002" gauge. Might take a few tries to get the feel of it.



Weird idle behavior, hesitation on opening the throttle. Cleaning the gunk is equally important as the adjustment, as the gunk alone case be a problem



Left one?

Not quite sure what you mean. Unless you have a v12 you have only one throttle body with a single throttle blade. The throttle body is attached to the intake manifold and has a cast aluminum elbow jutting out.

Cheers
DD
ho Doug

I will have to get a feeler.

when I said left I meant the left side of the butterfly itself. But you clarified when you said atv12 o'clock etc

I may ha e to come with questions if you dont mind.

thanks again. doug
 
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Old 11-23-2018, 10:13 PM
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It dawns on me that I can't really remember if the 'axle' for the throttle blade is vertical or horizontal. If it''s vertical you won't be able to take your measurement at the 12:00 o'clock position or 6:00 o'clock, obviously, so you'd take the measurement at 3:00 or 9:00.

Cheers
DD
 
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  #5  
Old 11-23-2018, 11:48 PM
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Originally Posted by Doug View Post
It dawns on me that I can't really remember if the 'axle' for the throttle blade is vertical or horizontal. If it''s vertical you won't be able to take your measurement at the 12:00 o'clock position or 6:00 o'clock, obviously, so you'd take the measurement at 3:00 or 9:00.

Cheers
DD
Hi Doug

Picture attached

So place feeler gauge where arrow is?

And where would the adjustment screw be?

Thank you

Chris





 
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Old 11-24-2018, 12:19 AM
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Your throttle bore is nice and clean

Insert feeler gauge at 9:00 o'clock position

Those are not adjusting screws

See how the throttle body is held in place with 4 bolts? Look at the upper left bolt in your picture. Just above that bolt is the adjuster. It takes a 5/16" wrench as I recall. Tricky to reach.

Cheers
DD

Cheers
DD
 
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Old 11-24-2018, 12:38 AM
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Originally Posted by Doug View Post
Your throttle bore is nice and clean

Insert feeler gauge at 9:00 o'clock position

Those are not adjusting screws

See how the throttle body is held in place with 4 bolts? Look at the upper left bolt in your picture. Just above that bolt is the adjuster. It takes a 5/16" wrench as I recall. Tricky to reach.

Cheers
DD

Cheers
DD
hahah cheers! I actually cleaned it out a little while back but had no idea about the butterfly gap. So now that I need to change the filter i figured i would have another quick clean up and also look at the gap to see thats it on the money. I feel monty idles a bit rough but to be fair i dont have anything to compare it to, having never driven a jag. But I figure cant hurt to check either way.

I see the screw. So when adjusting it essentially pushes up and down the arm which adjusts gap?

Would you recommend minor turns just in case? And do you recall which direction is open, clockwise or counter? I guess i can always experiment. I will pop over to Napa or harbor freight tomorrow to check for a feeler gauge.

Thanks again Doug







 
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Old 11-24-2018, 12:44 AM
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That's the adjuster screw, yes!

Can't remember which direction increases/decreases the gap.

Cheers
DD
 
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  #9  
Old 11-24-2018, 12:52 AM
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Originally Posted by Doug View Post
That's the adjuster screw, yes!

Can't remember which direction increases/decreases the gap.

Cheers
DD
Thanks Doug!

Will report back as soon as i adjust it, if it needs it of course!

Goodnight!

Chris
 
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Old 11-24-2018, 06:59 AM
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As the thrtoole throat is circular as is the butterfly itself, the feeler should be as narrow as possible - ideally a .002" wire and not a .002" broad blade. Trimming a blade style feeler will be as close to a wire as I could get. A blade that is too broad will result in a larger than indicated opening. This was my experience.
 
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  #11  
Old 11-26-2018, 09:37 PM
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So I adjusted the butterfly gap. Maaan that's a tough one!
couldnt get the spanner to it to give me enough torque. Finally stuck some old wd40 on it. Put some on a cloth and applied to the screw.

manged to get it to move with my fingers.

my question. What should be on the rev counter at parked idle? Currently have the needle at 10 and below 10 when transmission is in drive and I am braked.

thank you!
 
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Old 11-26-2018, 10:19 PM
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Originally Posted by chrisleg View Post

my question. What should be on the rev counter at parked idle? Currently have the needle at 10 and below 10 when transmission is in drive and I am braked.

thank you!

That's a bit high if the engine is fully warned up. Idle should be higher when cold, lower when hot. A device called the "AAV"-Aux Air Valve gives the higher idle when cold.

I've had best luck with about 800-850 RPM in "P". It'll drop 150 RPM when put into gear. The actual factory spec is lower than that (I can't remember what it is, exactly) but I go with what feels best, within reason. IME these old 4.2s are more comfortable with the slightly higher idle.

Info on adjusting the idle speed:
Idle Speed Adjustment

Cheers
DD
 
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Old 11-26-2018, 10:19 PM
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Originally Posted by chrisleg View Post
So I adjusted the butterfly gap. Maaan that's a tough one!
couldnt get the spanner to it to give me enough torque. Finally stuck some old wd40 on it. Put some on a cloth and applied to the screw.
Good work

Cheers
DD

 
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  #14  
Old 11-26-2018, 10:43 PM
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Originally Posted by Doug View Post
That's a bit high if the engine is fully warned up. Idle should be higher when cold, lower when hot. A device called the "AAV"-Aux Air Valve gives the higher idle when cold.

I've had best luck with about 800-850 RPM in "P". It'll drop 150 RPM when put into gear. The actual factory spec is lower than that (I can't remember what it is, exactly) but I go with what feels best, within reason. IME these old 4.2s are more comfortable with the slightly higher idle.

Info on adjusting the idle speed:
Idle Speed Adjustment

Cheers
DD
hi Doug

so you think at 10 in park is too high?

 
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Old 11-26-2018, 10:51 PM
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yes

Cheers
DD
 
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Old 11-26-2018, 11:01 PM
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Originally Posted by Doug View Post
yes

Cheers
DD
hmmm

I guess my next question, even after reading the link is what does this thing look like?

I cant see the wood for the trees at the moment!
😱

 
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Old 11-27-2018, 12:21 AM
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More info and pics in this thread

https://www.jaguarforums.com/forum/x...-screw-141875/


Cheers
DD
 
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Old 11-27-2018, 12:37 AM
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Originally Posted by Doug View Post
More info and pics in this thread

https://www.jaguarforums.com/forum/x...-screw-141875/


Cheers
DD
ahhh!!

I was on the right track! Actually took a photo of what I thought it might be.

My stubborn curiosity got me trawling the interweb and I found an article on a place called jagweb.

They mention also doing a "fuel trim" when adjusting idle. is this nessasery in your experience???

many thanks Doug!!!


 

Last edited by chrisleg; 11-27-2018 at 12:39 AM.
 
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