Idle Screw

[bpossel]

  Hello All!

 :?: Question....  what would be some possible causes of my idle screw having no effect on my idle?  When I remove the screw completely, then car stumbles...

Recent things done:
1.  Distributor rebuilt (Dan)
2.  Speed Relay & Switch rebuilt (Beckmann)
3.  New plugs, wires, ...
4.  New 17 degree switch
5.  New 100 degree switch
6.  New vacuum lines
7.  IP Pump rebuilt by Hans 2 years ago

Other current specs:
1.  Warm idle sits at ~800 rpms
2.  Timing set to 0 degrees at idle; 5 degrees BTDC at 1500 RPM
3.  Linkage set per our standard procedure on this site
4.  Air from IP Pump does shut off when warm

Also note: At warm idle, when I pull the vacuum line off of the venturi (throttle plate), idle (rpms) increases by ~200-300.

Any possible clues, ideas, suggestions, things to check next?  I am stumped...

Thanks!!!
Bob



bpossel  (Memphis, TN.)
'71 280SL  /  '97 E320

[enochbell]

It is very possible that you have a leak elswhere in the intake that is rendering the idle air path ineffective.  When you screw the idle screw in, near the limit, with engine running, can you hear the "hiss" of air through the channel under the screw?  If not, air is probably getting by somewhere else.  Could be as simple as the butterfly valve in the intake manifold or something tough like a leaking intake manifold gasket.  I would start with the butterfly valve, first make sure that the mechanism is spotless and in good working order.

Best,
g

'64 230sl, fully sorted out...ooops, spoke too soon

[bpossel]

Yes, I should have also mentioned that the throttle plate is clean and closed all of the way.

When I screw in the screw, I can hear a hiss..  Seems like a lot of air, vs no air...



Thanks!
Bob

bpossel  (Memphis, TN.)
'71 280SL  /  '97 E320

[Jonny B]

Bob,

Any leaks in the power brake line? Are all those clamps tight?

Jonny B
1967 250SL Auto

[bpossel]

Hi Johnny,

Power brake line is new, no leaks, tight.

Thanks for the post!

B.

bpossel  (Memphis, TN.)
'71 280SL  /  '97 E320