Turbo CSO running too high on idle

[alfredhamstra]

Hello all, got a small problem I cannot figure out.
Its my 1981 Turbo spider. Head and turbo were fixed (new seats, turbo overhauled).
New gaskets all around.
All original.
Problem is that it runs too high on revs when running on idle.
Cannot get it below 1500 rpm.
I searched for airleaks, cannot find any.
I sprayed airleakdetector everywhere I could, no result...
Changed the AFM, no difference.
The airbypass is closing after warm up, so thats also not the problem.

Second is that the car shocks a litle driving 40-50 mph. So small touch of the trottle makes it shock al little. Release the trottle a little, shocks also a little.

Anyone an idea where to look?

When driving 80-90 mph it runs great. Turbo kicks in nice...

greetings from Holland

Alfred

[18Fiatsandcounting]

The only reason that a Fiat DOHC engine idles too high is that it is getting excess air. Several possibilities as to why this might be, with the caveat that I have zero experience with a Fiat turbo engine:
1. Air leaks in the intake, but you've checked that.
2. Auxiliary Air Valve, but that appears to be working. Does it close all the way when fully warm?
3. Throttle cable too tight, holding the throttle body butterfly valve open.
4. Idle stop screw not adjusted right.
5. Idle air bypass is either leaking (the o-ring) or not adjusted right.
6. Ignition timing too far advanced.

As for the shaking, that could be worn engine or transmission mounts, a torn giubo (rubber donut), unbalanced driveshaft, bad U-joints, or possibly the wheels being out of balance. Or, you have a misfire in the engine and it's shaking. Did this problem start all at once, or has it gradually been getting worse?

-Bryan

[alfredhamstra]

Thanks for the reply.
1. Air leaks in the intake, but you've checked that: yes, sprayed everywhere, closed the hoses, no result
2. Auxiliary Air Valve, but that appears to be working. Does it close all the way when fully warm? Yes, closed it with a plier, no chancge when warm...
3. Throttle cable too tight, holding the throttle body butterfly valve open. No, all the way in, trottle closes on body even...
4. Idle stop screw not adjusted right. All the way in, trottle closes on body
5. Idle air bypass is either leaking (the o-ring) or not adjusted right. Also all the way in. Oring seams to be okay, still rubber, not plastic
6. Ignition timing too far advanced. Set it with a timinglight to 10 BTDC

I go this friday to a dyno bench test to let it adjust. Hope this gives more information.

As for the shaking: this problem I noticed after overhauling of the turbo and the head. So the drivetrain is till as it was before. Never noticed that before. Hope its connected to the idleproblem somehow...

Stupid old cars, nothing but headache

[alfredhamstra]

Found the problem: trottlevalve was not closing completely...
Adjusted it and now it runs like a dream...
Shocks are gone too...

Thanks all