930 idle unajustable

911tas · 07-20-2004, 06:56 AM

Hi all, I hope someone has a reply to this, My 76 turbo engine starts up with a slight rough idle at 1100 rpms. When warmed up it goes down to 600. I have tried to bring up the idle, but the only responce from the idle screw is if I turn it clock wise to far, she will stall, then when I back it out the only rpm's that I can get are 600.Fuel pressure is ok and all injectors are shooting fuel, there seems to be a slight missing at this rpm but hen incresing the revs, it goes away. She runs strong above 3000 and when the turbo spools up, all is working well, then when I bring her down she goes back to 600.
Any ideas would be helpful.
Tas

cowtown · 07-20-2004, 07:38 AM

Hi, I have a '77 Turbo engine.

Since you have already done the fuel tests and checked the idle screw (and probably checked for air leaks), you could check the timing. My engine's hot idle is extremely sensitive to how the timing is set.

beepbeep · 07-20-2004, 08:08 AM

Check CO as well. Low and uneasy idle often means lean idle mixture.

Paulporsche · 07-20-2004, 12:30 PM

Are you using the idle screw (big diameter) and not the mixture screw (3mm) to do this?

I have found just the opposite of beepbeep. On my NA car, a too rich idle fluctuates and prevents the rpms from rising. A pressure gauge connected to your WUR will tell you if your control pressures are OK, and if your WUR is working correctly.

Or, you can try leaning the mix slightly and incrementally (1/32 turn at a time) to see what happens. You can always set it back if there is no change or if things seem worse.

Do you have points?

cowtown · 07-20-2004, 12:39 PM

Inductive dist. pickup on the 930

beepbeep · 07-20-2004, 01:58 PM

Yeah, I also wonder which screw is being turned.

If you open the throttle-bypass screw and pour in some more fuel by adjusting the CO screw then idle must go up...

Paulporsche · 07-20-2004, 03:02 PM

beepbeep.

At some point, however, the too rich mixture, which is then being further enriched, will choke off, and send the idle speed down.

Then, if you lean the mixture the idle speed will go back up.

Try it sometime.

911tas · 07-21-2004, 05:28 AM

Thanks for the responces ,Yes It is the idle set screw that I am ajusting, the one thats located on the intak manifold. If bottomed out the rpm's will go down and stall the engine, I'll turn the screw counter-clock wise and restart the engine, the I'll start backing the set screw and the idle will pick up and stay at 600 rpm. If I contine to un-screw, it will come to a point where there is no further responce from the enginge and the set screw can litterly come out. I will do all of your suggestions listed that have not been done and will get back to this board. thanks

Tas

WERK I · WERK I's Garage

I suspect that the Aux Air Regulator is not fully closed when the engine has warmed up. This would defeat the effect the idle speed adjustment circuit. The idle speed adjustment circuit is much smaller in respect to the AAR circuit. I had a similiar problem with an SC AAR.

Paulporsche · 07-21-2004, 07:18 AM

If you try leaning the mixture the revs should go up. I would try this first.

If you search, you will find info on testing the WUR and AAR.