1983 Porsche 944 Idle adjust
11-27-2018, 04:21 PM
#1
4th Gear
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1983 Porsche 944 Idle adjust
1983 Porsche 944. If i close the air bypass screw all the way in, what RPM should i adjust the throttle stop screw to before i open the air bypass screw to the correct idle RPM?
11-27-2018, 04:44 PM
#2
Rainman
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you only adjust the throttle-stop screw to get the throttle sensor "click" for idle position with throttle closed.
adjust idle speed only via that bypass screw. California cars get 950rpm idle speed, i think it's 900 elsewhere?
adjust idle speed only via that bypass screw. California cars get 950rpm idle speed, i think it's 900 elsewhere?
11-28-2018, 08:26 PM
#6
Drifting
Good luck trying to get accurate rpm measurement. I don't know how the Porsche dealers do it, but the dash guage tends to read about 100 rpm high (from my observations) and at least one common diy tach/dwell meter that I own reads at least 100 rpm low.
On turbos, you can jumper a plug so the idle control valve is out of the picture. This allows you to turn the screw so that it idles the same with jumper in or out. Given that the ICV's job is to keep a factory idle rpm, I use that as my measure.
Of course, the O2 circuit probably throws all this off. Official procedure doesn't say to disconnect the O2 sensor, so I leave it in.
If the 83 doesn't have an ICV, I have no idea how you'll measure idle to within 50 rpm or even 100 rpm accuracy
On turbos, you can jumper a plug so the idle control valve is out of the picture. This allows you to turn the screw so that it idles the same with jumper in or out. Given that the ICV's job is to keep a factory idle rpm, I use that as my measure.
Of course, the O2 circuit probably throws all this off. Official procedure doesn't say to disconnect the O2 sensor, so I leave it in.
If the 83 doesn't have an ICV, I have no idea how you'll measure idle to within 50 rpm or even 100 rpm accuracy
11-29-2018, 12:36 PM
#7
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Is a jumper wire to the diagnostic plug needed on NA cars (more specifically, 1985.5) as well?
I'm still tackling a hesitation/stubble during idle and curious if I had accidentally re-tuned the air to fuel mixture for the worse, when I installed the throttle response cam...
I'm still tackling a hesitation/stubble during idle and curious if I had accidentally re-tuned the air to fuel mixture for the worse, when I installed the throttle response cam...
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11-29-2018, 03:19 PM
#8
Three Wheelin'
Is a jumper wire to the diagnostic plug needed on NA cars (more specifically, 1985.5) as well?
I'm still tackling a hesitation/stubble during idle and curious if I had accidentally re-tuned the air to fuel mixture for the worse, when I installed the throttle response cam...
I'm still tackling a hesitation/stubble during idle and curious if I had accidentally re-tuned the air to fuel mixture for the worse, when I installed the throttle response cam...
It has no effect on the air to fuel mixture though. It just controls the amount of air that can bypass the throttle plate. All the air that passes through the valve should still be metered.