Alfa Romeo Forums banner

1 - 20 of 22 Posts

·
Registered
Joined
·
183 Posts
Discussion Starter #1
Wasnt quite sure which room to put this in..

Anyway, i have a 73 GT junior which i converted to a twinspark engine and its been running ok. However, recently, when i turn the engine on, it starts reving itself until i turn it off. But not everytime, sometimes it will start and run normal.

I have done i couple of things before this started happening.

First is i have installed a stereo. So i have run a live from the battery and a negative to a point on the bulkhead where i have other things earthed. (no switched live installed as yet).

Second, i removed the valve cover to install a new gasket. I have check i reconnected two earths to the cover. (that was my hopeful thought).

Any ideas what could be causing this? The fact its intermittent seems to make it more difficult to identify.

Many thanks
Kev
 

·
Administrator
Joined
·
12,590 Posts
My guess is airleak on the engine inlet side, or something is affecting the throttle positioning sensor.

BTW: I do not understand the need to run an extra earth lead to the bulkhead from the battery. The battery should already be well earthed to the chassis of the car so running a wire to the bulkhead will not make any difference ... unless I missunderstood the comment :)

I assume your new wires are not playing with the throttle cable/links ... ?
Pete
 

·
Registered
Joined
·
183 Posts
Discussion Starter #5
My guess is airleak on the engine inlet side, or something is affecting the throttle positioning sensor.

BTW: I do not understand the need to run an extra earth lead to the bulkhead from the battery. The battery should already be well earthed to the chassis of the car so running a wire to the bulkhead will not make any difference ... unless I missunderstood the comment :)

I assume your new wires are not playing with the throttle cable/links ... ?
Pete
I thought airleak, but surely that would manifest itself everytime?

re the earth, may phrasing may have misled you. I meant an earth from the stereo to the bulkhead :)
 

·
Registered
Joined
·
183 Posts
Discussion Starter #6
just to mention, when it does it, its a perfectly uniform reving.
Ie revs to the same point, at the same speed with exactly the same gap inbetween revs.
Its not a hunting idle kind of rev.

I dont have a working tach at the moment but id guess its going up to about 2k RPM
 

·
Registered
Joined
·
183 Posts
Discussion Starter #9
I have tried disconnecting the stereo live and earth on the off chance that was affecting anything, but it made no difference
 

·
But Mad North-Northwest
Joined
·
10,535 Posts
If the car has Motronic I'd also check the Idle Air Controller. They can get sticky or go bad.
 

·
Registered
Joined
·
183 Posts
Discussion Starter #13
Its motronic yes. ICV is one of the things i considered..
Are they servicable or do they need to be replaced?

Cheers
 

·
Registered
Joined
·
183 Posts
Discussion Starter #16
I pulled IACV last night and gave it a good clean. The mechansim move freely manually, i have yet test resistance etc.
However, the sliding valve inside is permanantly slightly open, should it be like this?
Also, it like like there is a screw of some form going through the body of the valve, which look like it should be operable from the outside, but it looks like the head of the screw has sheered off?
 

·
Registered
Joined
·
183 Posts
Discussion Starter #17
Ok so, on the plug off the loom I get almost 12 volts on one pin and 0 on the other.

On the ICV I get a resistance of 7.5ohms...
 

·
Registered
Joined
·
1,751 Posts
Apply 12 volts to the thing and make sure it moves.
 

·
Registered
Joined
·
3,361 Posts
as in right on the edge of its life?
How do you check it?

Thanks
No, right on the edge of being adjusted properly. With engine off, it should click after moving the throttle a very small amount and you move the throttle plate on then off you should here it click.

Kevin
 

·
Registered
Joined
·
183 Posts
Discussion Starter #20
Is the adjustment via the screw that I don't have!?

I have out power to it and it seems to work well
 
1 - 20 of 22 Posts
Top