1096369

Hey Troops.

I have a bit of a basket case 1984 944..... Finally got it running (fairly!) reliably...... I just jinxed myself! Anyway been doing upgrades, new tire, shocks and struts, short shift kit, ect.... And have been having a ton of fun driving the hell out of a car that by all rights, was headed to the scrap yard....

Being an early car, it has a rattle at idle that will loosen your back teeth....the dreaded "early car shudder"! (Motor mounts are ok, but not great!) I increased the idle from 800 RPM to 1200 RPM and the car smooths out dramatically..... It is a different car at the higher setting..... Just sounds a little goofy!

Anyway.... I was thinking of switching to a late DME (and late AFM) to see if it makes any difference at the lower RPMs.... And of course thought about having the ability to add a chip for a couple of more ponies.....

I have a buddy with a late car who has offered to let me try his late DME and AFM..... Before I buy one.... What do you guys think, waste of time and money?

Thanks!
Fred

snb13

Not at all, as long as you swap both parts.

V2Rocket

The only difference you will notice is the lack of the idle judder.
Otherwise they are (almost) exactly the same in terms of fueling and spark timing.
One thing though...the late DME wants to see an idle control valve to..control the idle.
The early model does not have such a valve - only an auxiliary air valve which only aids in cold starts and basically shuts off once the engine is up to running temperature. After that an early 944's warm idle is regulated only by the throttle blade position (throttle stop) and the bypass screw.

jhowell371

You can adjust that shuddering out, I did it on my 84. it was it was 6-7 years ago so I forget where I read the how-to. A Google search should lead you in the right direction. I'll look around a bit and see if I can find it.

jhowell371

I found a link to the website (the944.com) where I got the instructions but the site is no longer up. If I remember correctly you used the air adjusting screw. You turned it one way or another (down I think) until you hear something click. I did it sixor seven years ago and wish I could help more but my senior citizen memory isn't what it used to be. Anyone else remember reading about or preforming this procedure?

PaulD_944S2

Still sounds like the motor mounts will need to be changed.

snb13

Without chipping the car you're only treating symptoms, not the cause. It's in the tune, though not present on all cars. Mine didn't have it, for example.

It has been well documented by FR Wilk, though none of his sights are up any longer.

jhowell371

Thanks SNB, I couldn't remember where I read it, it was FR Wilk's website.

V2Rocket

It is present in all 1982-1985 early model DMEs...
What happens to cause the judder is that as you let off the gas in neutral and the RPMs fall, the fuel injectors are "off", but they have to turn back on to catch the engine to return it to idle speed.

In the early model DME the RPM "switch back on" point is a few hundred rpm lower than it really should be, so the injectors can't catch the idle fast enough, so the RPM drops to 600 or 800 or whatever it gets to before stabilizing at 900-1000.

On the later models they raised the switch-on point to 1600rpm or so (early was like 1200) so its a much softer "catch" and return to idle.

What you can do on the early cars is either adjust the TPS so that closed throttle doesn't click the idle contact, or just adjust the throttle-stop screw (not the idle speed screw) to hold the throttle plate open just past where the TPS clicks. SO the car never actually "idles" but it runs at low stable RPM based off the AFM signal (very low part throttle to be precise).

PaulD_944S2

Spencer, good job explaining the drop to idle shake with its fix.

1096369

Interesting post guys..... Thanks for the help and advice! Since my buddy has a late car,
And is willing to let me pull out his DME and AFM, and see what (If any) deference it makes....but for now, I really don't mind the 1200 rpm idle...... While it is fast..... It is tolerable... My only bitch, is l do have a bad "buzz" in my dash.... It kicks in around 2800 rpm..... My solution is..... Turn up the radio! Hey it is a 32 year old German sports car..... If I wanted quiet.... I'd buy a Camry!

I am not entirely sure what it is..... ia loose screw, (driver) or a bad speedo cable, maybe even the fan behind the glove compartment (what the hell is that for anyway!) but for now..... Loud Warren Zevon, cures all issues!

Thanks troops!!!
F.

V2Rocket

hey, i have to do something productive while at work...
are you sure your balance shafts are timed properly?