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Idle rises to 5k - possible cause?


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If you haven’t got the Lock Nuts on that’s half the Problem as the Vibration will loosen the Rods and upset everything,you also need a decent Airflow Meter to balance the Throttle Bodies or again your wasting your time as the Car will never run right.

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If you haven’t got the Lock Nuts on that’s half the Problem as the Vibration will loosen the Rods and upset everything,you also need a decent Airflow Meter to balance the Throttle Bodies or again your wasting your time as the Car will never run right.

There is not enough room on the centre shaft for a locknut, I assume this is why the garage that fitted them removed all six. I do have some nuts but, as I say, there is not enough room to even fit one on the centre rod, I have used loctite however.

Edited by iani
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There is not enough room on the centre shaft for a locknut, I assume this is why the garage that fitted them removed all six. I do have some nuts but, as I say, there is not enough room to even fit one on the centre rod, I have used loctite however.

Ian

You definately need the locknuts fitted as per TrNial & all the rods should be the same length.Can you cut centre one & weld a piece in to make it longer (just a thought). Also check the Air valve is not allowing air past when its closed.

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Ian

 

You definately need the locknuts fitted as per TrNial & all the rods should be the same length.Can you cut centre one & weld a piece in to make it longer (just a thought). Also check the Air valve is not allowing air past when its closed.

If I made the rod longer the revs would go up, I have glued the air valve in place and don’t believe it is the source of any leak.

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I can’t believe the rod(s) are expanding that much to open the throttles. Say a 50-100deg temperature rise a 6 inch steel rod will ‘grow’ something like just about over 0.002” to 0.004”

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It is an interesting (and not unique problem).. I had exactly the same issue on mine a couple of years ago.. could adjust the rods for a lovely idle cold of say 800 rpm. Once warmed up it got to 1500 rpm (while with the rods disconnected the car would stall). then if I was brave (it is hot down there!) I could adjust the linkages to give an idle of 800-900rpm hot, but that meant they were hopelessly out of sync when cold. Became a bit academic when I replaced it with the supercharger. On reflection I wonder whether it was a result of the throttle bodies not being aligned with one another and differential expansion of the whole lot putting things out of whack!

Cheers

Tim

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I can’t believe the rod(s) are expanding that much to open the throttles. Say a 50-100deg temperature rise a 6 inch steel rod will ‘grow’ something like just about over 0.002” to 0.004”

I don’t have the problem with the engine cold, I don’t have the problem with the rods disconnected and the engine hot, the rods, or some other part of the linkage, are/is expanding.

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Here is a picture of my CP linkage, with the Pheonix manifold and underslung linkage, also with the ball jointed rods, I havent had any trouble with setting the idle, how does this compare to your setup.

post-4191-0-08400200-1529674757_thumb.jpgpost-4191-0-32061500-1529674803_thumb.jpg

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Hi Ian,

If you touch the throttle cable or fast idle cable ( move it out by say 0.5 mm or bend them a bit) , does the engine speed raise when hot (that should not be the case)?

Keep digging.

Waldi

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My linkage:

 

post-6710-0-97899400-1529687015_thumb.jpg

post-6710-0-95445800-1529687028_thumb.jpg

post-6710-0-71578200-1529687042_thumb.jpg

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Hi Ian,

If you touch the throttle cable or fast idle cable ( move it out by say 0.5 mm or bend them a bit) , does the engine speed raise when hot (that should not be the case)?

Keep digging.

Waldi

Hi Waldi,

 

There is free play on both cables so no, it doesn't change the speed, the fast idle cam is purely decorative, the profile is wrong

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Here is a picture of my CP linkage, with the Pheonix manifold and underslung linkage, also with the ball jointed rods, I havent had any trouble with setting the idle, how does this compare to your setup.

 

Yours looks like the original linkage John, unfortunately mine was replaced by a new version.

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Are you absolutely certain that those throttle bodies are perfectly aligned with each other?

It may be the angle the photo was taken at but.....Looking at the pictures the aft one looks like it needs to be tapped clockwise a bit.

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Iani

There are a few things I can see that are different to mine.

I have stop screws on each spindle, this will allow you to set the airflow for each body without the rods attached.

The screw on the choke needs to be wound in further, as this will you to lengthen the ball joint rods.

Also the adjusting screw in the centre should only have a minimum gap, this will be used later to increase the idle speed of all the bodies, once the rods are set.

Hope that may you now get it running properly, you need a good airflow meter, to set the butterflies first of all.

John

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Iani

There are a few things I can see that are different to mine.

I have stop screws on each spindle, this will allow you to set the airflow for each body without the rods attached.

The screw on the choke needs to be wound in further, as this will you to lengthen the ball joint rods.

Also the adjusting screw in the centre should only have a minimum gap, this will be used later to increase the idle speed of all the bodies, once the rods are set.

Hope that may you now get it running properly, you need a good airflow meter, to set the butterflies first of all.

John

John,

The fast idle screw is doing nothing, the cam is the wrong profile, the screw never touches it. The centre adjusting screw does have a very small gap. Two people have tried setting the butterflies to no avail, the stretching rods just screw up the settings, one attempt at setting the airflow correctly saw me being recovered after a 5k idle! (after a few miles driving). I just wish I had the original linkage and could follow the standard setup procedure, something is wrong with my setup and none of the people who have looked at it can see what it is. Things are improving, I have just taken the car for a 25 mile run and it's idling at 1300 now, close but still not right.

 

Ian

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Ian,I see you have an aftermarket Manifold fitted so have I,when I fitted my underslung Linkage the Centre Rod was fouling on the Manifold so I had to hit the Manifold with the Ballend of a Hammer to put an indent into it so the Linkage could work properly,is this why your Centre Rod was Cut Short.

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Ian,I see you have an aftermarket Manifold fitted so have I,when I fitted my underslung Linkage the Centre Rod was fouling on the Manifold so I had to hit the Manifold with the Ballend of a Hammer to put an indent into it so the Linkage could work properly,is this why your Centre Rod was Cut Short.

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No idea Niall, unfortunately I had it fitted by a garage, this has been the cause of a few of the issues ive had, they let an apprentice loose on it and he isnt very good.

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I've come in a little late here and maybe havnt read everything. Forgive me if I am sticking my oar in.

But simply put The metering unit works on vacum and that is controlled by the the engine sucking.

99% Its in the linkage.

Simply as others have suggested.

Take the air box off and see if at idle the butterflies are closed.

If they are and the car is still reving then you have a vacum leak

The rest is in how much the butterflies are open.

But if the butterflies are closed or near at idle then the revs cant be coming from there, the metering unit has to get its draw from somewhere.

So first asses the butterflies and after where air is getting in. After which you can trace back.

Tony

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