1978, US 5 Speed.

I just finished replacing vacuum hoses using the diagram in the WSM as well as reconnecting/unblocking the EGR valve and everything is now hooked up properly, I set the timing and the car runs great. The only problem is that it now wants to idle just below 500 RPM and keeps dying.

Per the WSM I've tried adjusting the idle screw in front of the throttle body but it seems to be stuck. I can't find any threads or anything in the WSM or PET that shows that there is any kind of set screw for this, so is it just that rusty? I soaked it for almost 24 hours in PB Blaster and I'm still unable to turn the screw in either direction.

Is there a lock of some kind to keep it from turning or is my next step pulling off the plenum and trying to turn it with something that will give me more leverage than a screwdriver?

Thanks.

Stephen
1978 5 Speed.
Copper Brown Metallic and Cork/Pascha (for a bit longer anyway)

 

I dont think its locked. Mine turned no problem. IIRC its spring loaded for tention

 

you are correct----no locks, spring loaded tension....it should turn freely without much effort.

it is however, two dis-similar metals (steel and aluminum) that tend to corrode with time.

it may be necessary to remove the plenum and throttle body, soak the throttle body for a much longer period of time, and then put the throttle body in a vise while applying a (proper sized) screw driver on the idle adjustment screw.....

edit: there is also an adjustment screw (allen screw) on the throttle plate linkage (driver's side of throttle body) that can be used to set idle rpm's. if you get no results with the front idle screw....this one may be your next adjustment.


short of that.....junk it and install one that works.


Good luck---




--Russ

 

That's what I thought.

I'll post an update after I get a chance to pull the plenum and throttle body off.

Thanks.

 

Is it possible to soak the screw with Kroil or PT Blaster without pulling the throttle body? I'm not sure there is huge advantage to pull TB for this alone. Of course if there are other problems or if you need to replace the TB, then removing it will help.

 

it may have been loctited in if the spring is missing. In that case heat should free things up .. Warning using heat around fuel can cause other problems so removing the part from the car may have to happen or you could try a soldering iron on the screw

 

The spring is there, but the spring and screw are both thoroughly rusty. I'll soak it down again tonight and if it still doesn't budge tomorrow then I'll remove it and see if I can heat up the TB and apply more torque to it when it's out of the car and hopefully not break it.

 

if you are actually pulling off the plenum just stick it in your house oven for 2 hrs at 300 and the screw should come right out. heat up and expand the aluminum housing and the iron screw will not expand at the same rate it should screw right out. just becarefull the aluminum will stay hot for hours and will burn like crazy if you touch it make sure you really cool it well before handling it

paul with 4 79 928s

 

Another thing you can try is to tap VERY gently on the butt of a large screwdriver while it is engaged in the screw, while the screw is soaking and while you turn. You just want to create a bit of vibration and shock, not hit it hard enough to deform metal.

 

Have you tried using an L shaped screwdriver to get more leverage? It may require removing a few items but that beats taking the plenum and throttlebody off.

Dennis

 

Good idea, Dennis -- or, even easier -- get a large flat screwdriver bit that's made to be driven with a 1/4" hex and put a 1/4" socket on it to get some torque.

BTW, after you get it loose, take it out and put some engine oil or just a very light hint of copper anti-seize on the threads before putting it back.

 

I have a new throttle body for $150 , good used for $50 .....so do not spend too much time fixing it or the hourly wage gets pretty low ! It does mean that if you break it is not that expensive.

 

I'll be trying most or all of the suggestions tonight after work and if none of them work then I'll be stopping by tomorrow at lunch and adding the used throttle body to my weekly infusion of parts.

 

or you could also use one of those impact drivers that you put a screwdriver tip in and wack with a hamer, you don't have to hit it like your tring to drive a spike home, just a good sharp rap may do the trick.

 

Thanks everyone. PB Blaster, time and some tapping seem to have done the trick. It holds an idle right at 800 rpm and all now seems good.

Now on to the electrical gremlins that are popping up.