Looking for some guidance with stalling problems after install of medium weight flywheel. New to forum and am grateful such a great resource is available to Porsche owners. Owned car for almost two years and love 964. Recent modifications include B&B exhaust, new air intake, top end engine rebuild, upgrade to 3.8L, sport cams, medium weight flywheel, and new chip. Really like the lighter flywheel but after installed with new chip continued to stall. Had Imagine Auto, KC, dyno and tune car. Now although car does not totally stall out the ilde is hunting between 200 and 800 rpm. The idle was stable before the tuning was done. I am aware of all shortfalls of lightened flyweel from the many postings on PCA website but was hopeful the andial medium weight flywheel would not be as bad as RS flywheel. I have read about possible solutions: replace idle positioner, oxygen sensors,idle stablizer valve, check spark plugs, clean battery cables, and check intake system hoses and hose clamps. I cetainly will have all these things checked. Steven Kasper at Imagine Auto is recommending I go back to the dual mass flywheel. Before I do this I just wanted to see if anyone else had any recommendations or a similiar situation. I read something about installing new parts & wiring for the "idle positioner" which were introduced for the 993. I don't know cost or feasiblity. Any help would be much appreciated. Thanks!

 

First of all... Welcome to Rennlist! Second... Welcome to the LWF stalling club! I have a LWF (not medium weight) and had stalling issues as well. The "fix" that came with the LWF stated that you should add a small length of rubber hose over the idle arm to increase the gap. This was a trash solution and didn't work. Eventually I got used to learning how to drive it with the stalling issue... Keeping it in gear until the revs were down to about 1000-1500RPM. This worked most of the time b ut not that well in rush hour traffic. I have a custom chip installed in mine that took away 90% of my stalling issues. My car is basically stock with the B&B exhaust and a few other mods. I think what you'll need to do is have your chip mapped live. You should also do a search here on "LWF" and "stalling" in the search parameters. You might want to limit the search to the 964 forum.

Another thing you might try is to get one of the diagnostic interfaces. (Buy or build) This has an idle adaptation feature that helps a little. You can search on "diagnostic interface" and you'll see A LOT of info on it.

Please post back how it goes...

 

A lightweight flywheel should not make the idle unstable when its just sitting there should it? When you remove the load from the engine and allow it to drop in rpm sure.

 

Heirsh... I see what you mean. Mine still has a small idle surge at times. I'm not sure if it's related to the Hall Sensor code that I have or not. I think that if you have a small problem with the idle that the LWF will exacerbate the issue.

 

Yeah that makes sense Rick. So he perhaps has something else going on that with a normal flywheel would simply be annoying.

If it went in ok idling and came out wrong perhaps something is disconnected. I'd follow your own advice and check all the stuff around the engine. It is so easy to forget a hose or a connector.

If I did it for a living I would have to make a sheet of everything I disconnected to make sure I put it all back.

 

It sounds like your mechanic has the best solution - go back to the DMF! Afterall, you bought this car to drive on the street where you will stop and go frequently - if it stalls, how is that frustration worth a small difference when accelerating in 1st and 2nd, and when heel-toeing into a corner (which on a street driven car doesn't sound too useful!)? Besides you have a 3.8L so you have more torque already... if this is a street car, a DMF sounds like the best solution!! On a race car, it is a worthy upgrade, for sure!

 

Thanks to all for the input and suggestions. I'll keeping working at it and fortunately the DMF is an easy enough solution. Great forum!

 

"medium weight flywheel."
The mid weight fw does not cause stalling on the 89 . Don't point at the 89 fw as the badguy .
You have so many mods , its hard to know whats what .

 

Yup... That is certainly the case!

 

Are you running an off-the-shelf chip from GIAC or did Stephen@IA burn you a custom eprom? If its custom I might be able to help you with a software solution. What model year is your 964? With the 19lbs Andial midweight flywheel you shouldn't have any problems with stalling if you have the stock ECU chip. Any problems with the MWF are usually hardware related but who knows what was done to your chip. Are there any active fault codes? (possibly intermittent hall sensor?)

 

I agree, no MWF stalling issues with a 3.6/3.8 stock motor.
You mentioned cams . What duration ? Too big and a flap system will go nuts !
and never be correct.
Is this a cat motor ? Is the O2 sensor working/connected ?
Before you set off changing parts the brief description has raised a few potential problem areas for me.
What has the tuner got to say ?

All the best

Geoff

 

Thanks for the additional help. I should have been clearer with the timing of the modifications. First, the car is a '90 C2 with 82k miles. The B&B exhaust, air intake and a GIAC chip were done originally. At this time car ran great other than very leaky engine. Five months later had a local mech. perform top end rebuild. I had him upgrade to 3.8L, install 993 Super Sport cams, replace dmf w/ Andial Carrera Cup unit, replace clutch disc., release bearing, guide tube, and replace clutch slave cylinder and hose. At this time the car would idle steady at 800 rpm but would stall immediately the first five minutes after start-up and then only when I deaccelerated quickly. I felt mech. did a very good job and was very maticulous. He came highly regarded. Plan was to break-in engine for 1K miles and then take to Stephen@IA, who has a great reputation, for new chip, dyno, and tuning. Stephen used GIAC chip. I believe he burned a custom eprom vs. off-the-shelf chip but will have to find out for sure.
Drove the car a week following install of replacement chip and idle was still steady at 800 rpm. Stalling would still occur during engine warm-up but did not stall nearly as bad as w/ previous chip after warm-up. Then had Stephen dyno and tune. Currently, the car does not stall out completey but idle is not steady and bobs up and down before and after warm-up everytime I'm stopped. Perhaps this is what it is suppose to be doing. I apologize for my mech. ignorance but the car is outragously fun to drive other than me sounding like I'm racing my engine at every stop. Maybe this is give and take and I can probably live with it as it is not my primary driver. The orginal mech. did discover later that the 89 flywheel sensor setting was .8mm which I guess had the lighter flywheel. He has offered to change to this setting if it indeed does effect the idle. That is the long and boring history of my car. If I would have not been so stubburn and listened to the many postings on the 964 "LFW" problems I would not be asking such stupid questions and wasting everyone's time. Anyhow, thanks again for all the help and these cars are great fun.

 

If the motor runs OK I would not believe that the sensor/flwheel clearance is an issue .That is pretty much a go/no go situation.
If the overrun shut rpm change has been done in the chip , then all thats left are the cams .I dont know for sure what duration 993 Super Sport cams have
but the flap DME system is not happy with big duration cams . The 993 MAF
system is much more accomodating.
Sounds like the chip content should be revisited and overrun checked out + some more work on the idle system .
Be good to know the cam specification.

All the best

Geoff

 

There is always the Motec solution.

 

Why Motec ? There is nothing wrong with Motronic . First step is to understand why this motor has stalling issues . For example ,Motec wont fix incorrect cam timing !

Geoff