Drop and Shutter Fix Q's

944_science · 07:59 AM

Since I bought the car it had the idle drop and shudder symptom. I followed fr-wilks's procedure found here: www.the944.com, to bypass the TPS and set the idle with the throttle body air bypass screw. I have a late (85.5) DME and AFM so my question is what is the cause of this in the late model, as I thought this should only effect early cars? I was thinking of getting wilks's chip which should remedy this, but was looking for some incite into the root cause...... software bug, bad TPS???

Many Thanks

944_science · 07:59 AM

The TPS tested Okay per Clark's, anyone else have experience with late model shudder and using wilk's chip as a fix?

TTT

914efi · 01-07-2010, 05:50 AM

Root cause is that fuel shuts off totally (and sharply) when you close the throttle. That is probably the reason for the throttle cam that everybody removes, it helps to smooth the transition due to more mechanical advantage at the closed throttle end of travel. I have seen the bypass fixes, but I was wary of them.

I think the chip(s) fix it properly, but not sure. It is nice to have the fuel shutoff when coasting (saves gas) but annoying trying to drive smoothly at low speed.

looneybin · 01-07-2010, 07:25 AM

i fixed it with a FR Wilks chip
I don't know how it works, i'm not a computer science guy, but it fixed the shudder and also got rid of the flat spot at 3K rpm

944_science · 01-08-2010, 03:51 PM

It seems strange that porsce would design the fuel delivery this way. I always thought it was a software bug or an engine electronics malfunction.

Quote:

Root cause is that fuel shuts off totally (and sharply) when you close the throttle. That is probably the reason for the throttle cam that everybody removes, it helps to smooth the transition due to more mechanical advantage at the closed throttle end of travel. I have seen the bypass fixes, but I was wary of them.

I think the chip(s) fix it properly, but not sure. It is nice to have the fuel shutoff when coasting (saves gas) but annoying trying to drive smoothly at low speed.

ParkerFya · 01-08-2010, 07:14 PM

If you have a late DME and AMF in a early car, will the chip help with the shutter?

944_science · 01-09-2010, 03:53 PM

Quote:

Originally Posted by looneybin

i fixed it with a FR Wilks chip
I don't know how it works, i'm not a computer science guy, but it fixed the shudder and also got rid of the flat spot at 3K rpm

Thanks guys for the response, I ordered wilk's. He said as stated on his website that the shudder fix is built into the chip and should solve the problem. I'm also excited to see how the car feels with the shift in the power band.

zedsn · 01-09-2010, 04:38 PM

I was very happy with the Wilk's chip in my early 944. My DME had a switch for factory setting or chipped setting. Needless to say I never used the factory setting.

ParkerFya · 01-09-2010, 07:06 PM

zedsn, is your chip for the early DME or late?

zedsn · 01-09-2010, 07:14 PM

Mine was for the early 944 and isn't as easy to install as a later DME. The early computers have to have the chips soldered in. I bought my Wilk's chipped computer used here on Pelican and to me it was well worth the money. No big HP gains but car ran smooth and had no flat spots during acceleration. I think it gave my 83 NA like 5 extra HP.

ParkerFya · 01-09-2010, 08:52 PM

Thanks, I'm not to worried about the HP gains, Just a more smooth running motor.

Did the chip help with the shutter?

I was also looking at the swap to late DME and AMF cause I've heard it makes it run smoother.

zedsn · 01-10-2010, 04:24 AM

Yes the chip fixed the shutter. You will have to take a late AFM and DME and use them together and I have heard the same thing but don't know for sure though. There was also a write up on pelican about fixing the shudder a couple of years back and it supposidly worked. Maybe you might want to look in the old threads and it won't cost a dime.