84' Idle Issue

[firefighter7128]

does not look as if anyone has opened this before

[924Sman]

Then I would place a wager you suffer the "shudder" issue. This if true may be a bit more difficult to fix since the only guy I know doesn't make the board any longer, this is my understanding that is but I may be wrong and FRWilk has more to sell. Place a WTB ad for the DME w/FRwilk adapter board to fix the shudder issue, I do recall seeing one ad a while ago. And I do not think Wilk is able to be reached since his PC crash...so to speak. There are some members here who have been able to do business with him, ask around here for an email for him.


www.frwilk.com

Dal

[firefighter7128]

as a reminder, i have a rich fuel smell as well. i found that after siliconing the shifter boot down i got rid of the exaust smell. but im wondering if the O2 sensor is bad, telling the car to send more fuel. i dont know. tossing it up in the air.

[white944cup]

Here is FR Wilk's fix for the early 944 idle shudder. I made this adjustment on my '84 that I just sold to rcecale....it had a bad shudder, and the adjustment smoothed it right out.

THE PROBLEM:
What is the "944na shudder"? Every time you close the throttle from above
2,000RPM, the engine drops below the normal idle of 950RPM down to 600RPM
and then back to 950RPM. The engine performs a violent shudder. The
intensity of the shudder may vary and many 944na Porsche do not have the
problem.
NOT THE CAUSE:
Response cams, spark plugs, vacuum leaks, motor mounts, and auxiliary air
valves will not cause this shudder. They can cause idle problems or engine
shaking but have nothing to do with this specific problem.
THE CAUSE:
On deceleration, the overrun [coasting] fuel cut-off frequency is too close
to the idle frequency. In other word, fuel is cut-off when the throttle is
closed and does not start up again until the engine drops below 1,200RPM.
Fuel does not start up soon enough to keep the RPM from dropping below
normal idle. The overrun fuel cut-off frequency should be set higher at
1,600RPM. It is designed to save fuel. Mine dropped to about 600RPM with a
nice big shudder.
THE CURE:
The overrun fuel cut-off frequency is internal to the DME. If the
throttle-closed signal is never received, the overrun cut-off will be
eliminated. This is a simple trick to fool the DME into ignoring the
fuel cut -off. The software fix is beyond the capabilities of most,
but this simple adjustment, anyone can do.
THE PROCEDURE:
Do not continue if your engine is not in good working order. Fix it first.
With the engine off, take an 8-mm box wrench and loosen the nut on the
throttle stop screw. Operate the throttle so you hear the click. Turn out
the stop screw until the click stops. Turn the screw out about a quarter
tun past that point. Tighten the nut and lock it down. Start the engine and
turn the air bypass crew in to adjust the idle down. Set it a little high
at about 1000 RPM. What you have done is completely eliminate the
throttle-closed switch.

[rcecale]

Hey, Terry!

This is that screw adjustment that you had performed that you showed me on Saturday, correct?

Randy

[white944cup]

Randy:
That's it.....it's easy to change back if you want to see what the shudder is like. It was pretty bad and it made the car a PITA to drive in stop-and-go traffic, when you are letting up on the throttle a lot. Did you take your ride up into the hills on Christmas Day? How was it?
Terry

[bearone2]

whether it's the light or something else, it looks like the k&n air filter is real dirty.

[rcecale]

Terry, change it back??? Nahhh...sometimes it's just better to read about something and get your understanding from that. She's running just fine and my philosophy is, If it's not broken, don't fix it!"

Didn't get out Christmas day like I wanted to. It was a really nasty day, weather wise. Cold, rainy, overcast. Really kinda regretting that decision today though. Had my shoulder done yesterday, so it's gonna be a while before I drive it...well, any kind of distance, anyway.

I failed the GA Emissions test on the 24th, for excessive CO (She read 3.48 when allowable is 1.08 @ 1953 rpm - 25/25 test) Looking through other posts on the subject, it seems the O2 Sensor is where I need to start. I'll probably have Ryland have a look at her too. He wanted to put her up in the air and give her a once over anyway, so...

Back on topic of this thread, I have to agree with bearone2 about the appearance of the air filter. Looks way dirty, none of the telltale red color of a freshly cleaned filter. If the car can't breathe, you're gonna have issues!

Randy

[juVius]

pm'd you...

[Gary2397]

Sounds to me your TPS(Throttle Position Sensor is bad). My 1983 944 idle did the same thing.
Get the instructions on how to check TPS. Clean and re-oil your filter every 30K or 50K miles.
TPS contained idle contact, ground, and full throttle contact.

Your car has an Auxiliary Air valve which add extra air when you first start the car cold.
Check this Auxiliary Air Valve and coolant temperature sensor too.

Upgrading your stock Throttle Response Cam with redesigned 944 cam by Weltmeister is not a bad idea if idle issue solve.

[Gary2397]

Sorry about the second post. I thought the first one did not go through

[firefighter7128]

over the weekend i replaced the throttle screw that snapped of with a 5mm screw and a nut to lock it in place. car runs sweet. still has a shudder issue. i still have to sit out in the car for a few while it warms up, but once it has a min of run time it will stay running by its self.
for now im going to move on to plugs cap and wires and make any adjustments needed after that.