[BRUNO]

My brother in law brought his79 gts over last weekend fo a little diagnosis. It seems that when it goes for a while that the throttle cable might be sticking almost giving the car cruise control.Upon examination it is free and does not stick at all.It only does it when car is up to operational temps. It can be made to do it in idle. I am thinking emissions??? Any input???

 

[Magoo]

Bruno, Has anybody messed with the fast idle setting? Under the air box on the right side there is a small tower on the intake with 3 10mm bolts holding it down and it has a eccentric cam on top of it that rides on a adjustment screw on the linkage. If some body raised that cap and got the arm disconnected from the fast idle spring it could be that or reversed the spring. Also a vacuum leak like a intake that opens up when warm. Same for carb. base to intake. Make sure all are tight and do not over torque the carb. base gaskets. But to me it sounds like with cooler weather the fast idle spring is messed up.

 

[BRUNO]

car has been sitting since 1991. I dont think it has been touched. It could be a lot of things from the long sit. It is interesting that it does not do it when car is cold. Car must be brpught up to operating oil temp for it to happen. Will check what you said this weekend if I get down there. He is moving down to the Delaware,Pa state lines and needs to drive all 11 of his cars down there about an hour. I think it is managable the way it is but it's got to get resolved sooner or later.

 

[bretm]

Fast idle system would be the first to check like magoo says, it's the most likely cause. After that I would look for vacuum leaks.

 

['75 308 GT4 (Peter)]

Here is a picture of the fast-idle device.

I'll also add - and it can be embarrassing when you discover it - that it could be suffering from the Ferrari-cruise-control-syndrome...

ie: The floor mat slips forward and presses on the throttle pedal.

It sounds silly, but its happened to the best of us...

 

[BRUNO]

Nice engine Peter.
No it's not his mat.
Must be this. Betting it's vacum from emission system.He runs with no belt on his pump But I doubt thats it as a lot of people do it. I am thinking vacum leak (Magoo). What if I just unhook it all together for now.Other than tough starting in cold what is downside. When I say unhook I mean the linkage.

 

[BRUNO]

Hey if this was a 400i he'd be driving by now.

 

[Magoo]

Bruno, When you remove the fuel rail that lays over the cap and remove the 3 10mm bolts there are two sections. There is the cap with the cam on it and there is the plate underneath that holds the spring diaphram. The pin that is on the cam shaft sticks down and is supposed to go into the loop hole, of the spring. Then the whole assembly will have to be put back on as one piece. When the cam turns from the heat of the intake it should decrease the idle. If it does not and speeds up the idle someone has installed the spring upside down. Repeat the proceedure above and flip the spring.

 

[Magoo]

Also one more thing, When you put the entire assembly, cap and plate down on the intake then rotate the plate on the bottom, using a long shaft small head straight screwdriver so the cam is on the high side against the fast idle screw with the engine cold. Then watch the cam as the engine heats up. Accellerate occasionally to let the cam adjust toward the low idle position against the fast idle screw.

 

[Magoo]

The answer to the other question you just asked in regard to removing the linkage to the fast idle. Just back the fast idle screw out all the way . Of course this doesn't solve the problem but you could see if it is the culprit.

 

['75 308 GT4 (Peter)]

Magoo, if you look at that first photo I posted, you may see that I have removed the screw altogether - a correct method for disconnecting the system.

Here's a picture of the coiled spring and the cam's arm-and-peg. Obviously, the peg must fit in the loop at the end of the spring.