Idle Drop

AFPorsche · 03-25-2001, 12:04 AM

Need some help...85.5 944N/A, manual trans. Starts fine, idles at 900rpm. Acceleration is smoothe. Problem arises as I approach a stop or slow down. As I slow down, come close to full stop, idle drops to about 500-600rpm, sounds like it wants to stall then jumps back up to 900rpm. Then idles and accelerates fine. It is especially problematic when I am running the A/C. Car also jumps a bit when cruising at slow speeds (20-30 mph). Recently replaced spark plugs, air filter, fuel filter, DME Relay. Any help would be greatly appreciated.

Lawrence Coppari · 03-25-2001, 03:57 AM

While this probably won't help much I have a 400E that used to do exactly that. Turns out the sensor that determines where the crank is in its rotation was the problem. Dealer found the problem and replaced the sensor. Problem is gone.

Just a thought.....

Ehab · 03-25-2001, 11:53 AM

AFPorsche, see my response in the thread titled 'Funky idle', you basically have the same problem, and could fix it with the 'Second thorttle screw' I mentioned. Basically, you have too much dirt in your throttle plate, so when it closes quickly, the rpm drops too quickly too low. You just need to open it a bit to let it breathe, then adjust the idle rpm with the normal idle screw.

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Lock Stock '84 944 and two smokin' tires ...

AFPorsche · 03-25-2001, 03:20 PM

Can you help me out with the location of the other idle screw. The only thing I see, is the idle screw (yellow paint) and the throttle body cable adjuster. Is the adjuster the other screw you are talking about? If so I will press on with adjustment...if not, please help. Thanks in advance.

Ehab · 03-25-2001, 03:36 PM

The other screw is close to the idle screw. If you move the throttle plate by pulling against the cable, you will see that when you release it, the springs bring the shaft back to close the throttle until the cam hits the screw that I'm talking about. It is very small, and might not look like a normal screw, but it is threaded all the way through, and can be moved (after loosening the nut that holds it) with a flat blade screw driver ...
Good luck

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Lock Stock '84 944 and two smokin' tires ...

AFPorsche · 04-02-2001, 09:10 PM

Ehab...Thanks for the info. I was able to find the throttle screw. Made some slight adjustments this past weekend. Seems to be running a little smoother. It still seems to jump at low, constant speeds, though. Any relation to the throttle adjustment screw? Thanks again for the help, I'll keep adjusting until I get it right. I'll let you know how it turns out.

Ehab · 04-03-2001, 08:12 AM

AT this point, all I can advise you to do is to take out the intake boot, then remove the throttle body (with the allen screws) and CLEAN IT VERY THOROUGLY WITH CARB CLEANER, if your throttle body is old, it will have alot of gunk in it, make sure you get all the little vacuum hose openings and the plate itself and the idle screw seat ... it made my car run very smoothly afterwards ...
Good luck,

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Lock Stock '84 944 and two smokin' tires ...

vas deferens · 04-04-2001, 06:16 PM

the throtle screw is factory set....you should'nt be messing with it...if anything clean the throttle body and idle stabilizer...most likely the idle stabilizer.....vas

kukunaokala · 04-04-2001, 09:30 PM

This idle dip seems to be an inhererent problem with 944's especially when the AC is on. I'm going to try a dampener when my car is off the jack stands. See http:// members.rennlist.com/martintaylor/

As for that other slow speed tick, check the basics, fuel pressure/ volume?

Aloha, Neal

[This message has been edited by kukunaokala (edited 04-04-2001).]