PChar

I ran my car at a local Autocross event, this weekend, and some other P-Car owner said that I may have a vacuum leak on my car based on sounding and throttle response... I am not a mechanic, but I do experience throttle lag with a long woooshing sound before it actually rev. I always though it was normal with these old mechanical fuel injection systems.

I searched here and on pelican, but couldn't find any info at all. Anyone can explain what this little part actually does: 964 110 950 01 it is a check valve located on the intake with several small (1/4 ich) lines routing into it.

Thanks for the help,.. also please provide insight as too where and how should I go about troubleshooting for vacuum leaks.

Thanks

Rocket Rob

I am not near my car at the moment but it looks like the check valve that supplies a vacuum to the reservoir for the intake plenum flap.

PChar

Thanks Rob,
What are the consequenses of a failliure of this check valve?
Also any ideas of what the small black part# 964 110 652 00 it is listed as a "muffler" lots of tricky thing on this engine I have no ideas what they do or how they work,...

Thanks again for any info you can provide.

Rocket Rob

The early cars with magnesium intakes don't have the "muffler". That's unique to the plastic intake cars. Not sure what it does other than to guess its trying to dampen out a harmonic in the intake system. But that's a guess.

XR4Tim

I would guess that the "muffler" is there to quiet down any whistling that could be created by the idle speed adjuster as air is sucked through it.

PChar

It took me well over six month to troubleshoot my throttle response lag. But I think I finally figured it out. I red several, most likely well over 100s of posts here and on Pelican and the most common culprit is the barn door AFM.

These were the most helpful link to me, but in short I opened the AFM and perform the wiper arm move/slide and re-install for a fabulous restoration of power and throttle response.

http://www.the944.com/afm.htm



Most useful, check out Steve Wong post #17 here:

http://forums.pelicanparts.com/porsc...ming-stop.html

PChar

Another thing that also greatly improved my throttle response was this little filter I finally decided to change it, not sure what it does but figure after 20 years can be working as it was intended. So for $14 it was all well worth it.
Now the car growls and revs up at demand,.... no more wooooooshing at the intake.

ChaseN

Great news you've fixed it! I remember seeing this thread last year. Nice to see you post the solution for future members having the same issue who find this thread.

FYI the 964 is electronic fuel injection, not mechanical, and as you know now, should respond instantly to throttle inputs

m3vs911

Hi,

I've been reading posts in rennlist for many months due to my poor /lag throttle response but still no help.

After reading your posts which came to a success now I really want to try and fix my 964 back to normal if possible

I experience lag throttle response below 2500 rpm when the engine is warm up(3 mins after cold start) every time but the throttle seems fine to me if the rev is above 3000.

When I am looking to your pic you mentioned a little filter , can you please point out clearly to me which part is it in the pic ?

I've already replaced a rebuilt AFM, New ISV, new battery but all these didn't give me a significant improvement...

I wanted to look into vacuum leak but it doesn't seem easy to me.

dlpalumbo

Methinks the pictured item may be a vacuum check valve. Regardless, your symptoms are similar to those you would experience when your car needs a fuel adaptation. Makes all the difference in the world in low rpm throttle response. You need the Bosch kts 300 code reader or pdt 999 clone for this.

Good luck,

Dan

PS. A neat way to find a vacuum leak is to use starting fluid. Get car warm and idling. Then spray fluid around suspected areas. If idle stumbles you found your leak.