Hi guys, I've got a carburetor problem on my stock '81.  I just bought the car and when I start it, it idles REALLY fast, like around 2500-3000rpms fast.  Even when it warms up and I hold the primary open and nudge the throttle, it doesn't kick down.  What could be the problem?  When I look at the idle set screw, the linkage isn't even touching it.  I am mechanically inclined but have very little experience with carbs and I was wondering if there was something obvious that I could do or look at?  I really can't afford to get a new carb and if I were to rebuild I would attempt to do it myself. I'm wondering if it could be a vacuum problem.  I see a couple of hoses disconnected and cracked. 

Check to see that the secondary throttle blades are closed with the engine off. They will sometimes hang open a little, if they get some gunk built up on them. That would cause a fast idle speed, and it's something a lot of folks never think about. If you can't find a problem with the choke/fast idle set screw, look at the secondaries.
I have the vacuum diagrams, but they are on another computer here, that is not hooked up right now. If no-one else can get you them, let me know, and I'll set my other 'puter up and send them to ya.

If the idle set screw isn't touching anything then the
idle cam stuck is looking very guilty. It's hidden behind
the electric choke unit. Check the solenoid on the other
side of the carb also, it is supposed to activate only when the air con is on, and gives the throttle a wee shove to
make for faster idle (offsetting air con load)

GM Workshop manual has excellent info and vacuum diagrams. I have a bunch of PDF's and JPG's for your E4ME carb (yes been there done that!) so if you give me your email address I will send them to you.
CeeDee2008-04-04 00:34:55

That's too fast... Something is jammed up.....

Is the fast idle screw on my 79's carb in the same location...passenger side?

I got my carb back on last night, and after charging the battery fired her up this morning!! It seemed good, just a high cold idle.  It's around 1500.  I'll have to back it down next time I start it.  What should it be, and which screw do I want to adjust?

Adam, if the 79 is same as 81 then there are four items which affect idle speed...

1) the cold start cam, operated by the spring in the cold electric choke when you first press the gas pedal before starting. If the cam has operated it takes precedence over the other three items.

2) the "cold idle" adjust screw is on passenger side, in behind the vacuum break. It sits against the cam when the cam is operated, so its position adjusts the fast idle rpm for all steps of the cam while the cam is in play. Once the car is warmed up and the electric choke has rotated the cam fully out of play, this screw ceases to have any effect (unless mal adjusted badly enough I guess ! ) At this stage we now have a "hot" car.

3) With a hot car the idle speed is determined by the idle screw adjustment on the driver's side of the carb. It can be easily seen with the air fiter off, is at the front drivers side pointing rearwards towards the windscreen. Once you know where it is you can get to it ok with the air filter back on.

4) Lastly there is a solenoid on the drivers side of the carb which is operated when the air con is on. When off its plunger is far enough back not to be pushing on the throttle linkage. When on the plunger comes out and pushes on the throttle linkage, giving higher idle rpm. This rpm is adjusted by the nut/bolt on the end of the plunger.

So theway I have learned to adjust my idle on my 81 is...

-adjust cold idle first when on the highest step of the cam (which is where it should be when cold after pressing gas pedal. Quick check before pressing gas pedal is whip air cleaner off, choke plates on top of the primaries should be almost fully open. Operate throttle linkage, choke plates should snap fully closed. The same electric choke spring tension which does this also rotates the cold idle cam. Start the car, do not touch gas pedal. The choke plates should have immediately cracked open maybe an eigth of a inch or less if the vacuum break is working correctly. In this position the highest step of the cam should be in play, and highest cold idle speed can be adjusted. Don't touch the gas pedal or throttle linkage, cos as soon as you do the cam will rotate to a lower step !

-once car fully hot, and the gas pedal has been operated a few times along the way (allows idle cam to rotate) check choke plates wide open (means electric choke is working correctly, and cold idle cam should now be out of the way). Check air con solenoid is off and there is a gap between the end of its plunger and the throtle linkage = it is not interfering. Then adjust hot idle screw for correct idle.

-turn air con on, and adjust solenoid plunger for correct idle.

I had real problems getting my head around the idle cam thing because you can't see it and none of the manuals show it very well. So I bit the bullet and pulled my electric choke off just so I could see it all. Then all the bits of the jigsaw fell into place !

I will try and give a detailed explanation if anyone wants one, just let me know.

Have fun !

(oops... I referred just to the primaries in my original post, but to be totally clear it is actually the choke plates on top of the primaries, so I have amended the text )CeeDee2008-04-05 03:02:34

Thanks for the great and detailed response.  That explains things very well.  I'm going to check it now.  Regards, George