Air leak

['74Turbo]

Howdy folks!  I recently unearthed my car after having parked it for four-plus months, and it's idling terribly.  She only intermittently holds an idle, and when she does, the idle's very high (2100-2500 rpm).

 

I'm thinking an air leak, but the car was totally fine before I moth-balled it, so that seems strange.

 

Anyone else experienced a similar issue, and, if so, what was the rememdy?

 

Thanks,

Mark

[Preyupy]

Have a look at the back of the injection pump at the arm with the “verboten screw”. When the engine is up to temp is the screw touching the stop?  If not the warm up regulator in the pump is not moving correctly and the cold start air passageway is still open ( your air leak). You can also try pinching off the hose between the pump and the intake plenum, if that drops the idle speed the valve is stuck.  There are other possibilities but start there, it’s the easiest thing to check. 

[jgerock]

16 hours ago, Preyupy said:

Have a look at the back of the injection pump at the arm with the “verboten screw”. When the engine is up to temp is the screw touching the stop?  If not the warm up regulator in the pump is not moving correctly and the cold start air passageway is still open ( your air leak). You can also try pinching off the hose between the pump and the intake plenum, if that drops the idle speed the valve is stuck.  There are other possibilities but start there, it’s the easiest thing to check. 

+1.   I always suspect the hose between the pump and intake plenum.  Any leaks on that hose will create a high idle condition.

[dlacey]

Follow Jim & Byron's advice above, and if that most likely cause is eliminated, second area of risk - especially after standing for some time - could be a brake booster air leak...disconnect/plug the pipe to the plenum to see if this is your cause. 

If yes then maybe the booster will "fix itself" with some heat/cool cycles (that's my experience anyway).

[Einspritz]

What do your plugs look like? One or more fouled?

 

I've found this to be a chronic problem....

['74Turbo]

Sorry, guys, neophyte here.  When I look at the back of the pump, the only screw I do see does not come into contact with anything.

 

Anything further description-wise or especially pictures would be super helpful and greatly appreciated.

 

Best,

Mark

[Preyupy]

3 hours ago, '74Turbo said:

Sorry, guys, neophyte here.  When I look at the back of the pump, the only screw I do see does not come into contact with anything.

 

Anything further description-wise or especially pictures would be super helpful and greatly appreciated.

I'll pull one of my spare injection pumps out this weekend and get a picture for you.  The screw should not be touching the stop when the engine is cold (this is the cold start enrichment)  when the engine is up to temperature  the tip of the screw should be touching.  If this screw is not moving from cold to warm the warm up regulator is not working and the auxiliary air bypass (gives you a fast idle when cold) valve is not working either.     

[dlacey]

Here's the screw/stop on my car:

 

You can see the yellowish colour stop just below the hose clamp.

And here you can see the end of the screw with locknut...and the stop at the centre of the pic (ignore the hose clamp at the top of the pic).

When warmed-up that screw moves down to touch the stop...if it doesn't move down then the Warm Up unit or mechanism is faulty. That will cause high idle and over-rich mixture.

['74Turbo]

Many thanks, fellas, for the help!  I'll give it a look!

 

Best,

Mark