Unstable idle, stalling with LWF: Oxygen senor?
12-22-2010, 06:59 PM
#16
Nordschleife Master
I have similar symptoms ... idle dipping of approx 100 rpm .. drops to 750, bounces to 1000, settles at 850rpm - fairly consistently but sometimes it is perfect and about once per mth it has stalled. Generally worse when cold.
Tried ...
ISV has been cleaned so that it would 'rattle' freely in my hand
New Steve Wong chip
DME solder joint repairs
O2 sensor replacement
Would like to try an adaptation but trying to avoid dealer.
Tried ...
ISV has been cleaned so that it would 'rattle' freely in my hand
New Steve Wong chip
DME solder joint repairs
O2 sensor replacement
Would like to try an adaptation but trying to avoid dealer.
12-22-2010, 07:27 PM
#17
Three Wheelin'
Mine has lwf, was v lumpy till custom re-map.
Stalled sumtimes, mainly when under load, lights+heater ect;
After re-map lumpy idle gone, but stall issue not gone completley all thou a lot better.
Worse when v cold and under large load, heater+lights+low rev trafik!
Ive since raised the tick over on the throttle rest point, moved it slightly, mayb 2 mm.
Fixed!
Never stalls, ever.
Dipps a little when under load, but never stalls.
Tick over is up mayb a 100rpm at most, about 800rpm at a guess.
No one has ever commented about a high tick over, sounds the same as over 64,s.
Mayb it was set to low?
Nxt time i get the old girl out ill check proper.
Didnt cost a penny/dime, gotta be worth a try?
Stalled sumtimes, mainly when under load, lights+heater ect;
After re-map lumpy idle gone, but stall issue not gone completley all thou a lot better.
Worse when v cold and under large load, heater+lights+low rev trafik!
Ive since raised the tick over on the throttle rest point, moved it slightly, mayb 2 mm.
Fixed!
Never stalls, ever.
Dipps a little when under load, but never stalls.
Tick over is up mayb a 100rpm at most, about 800rpm at a guess.
No one has ever commented about a high tick over, sounds the same as over 64,s.
Mayb it was set to low?
Nxt time i get the old girl out ill check proper.
Didnt cost a penny/dime, gotta be worth a try?
12-23-2010, 09:28 AM
#18
Racer
I saw the response from an RS 964 that does not stall, but thats because the mapping of the ECU is
set for the RS (with LFW) modified 964's have the standard mapping (for a dual mass FW) so
stalling can sometimes happen. I have the RS clutch kit and when I stop the revs drop to about 100 and then the ECU searches the right timing/mixture and finds it at about 800 revs... 'but sometims it stalls..
I can live with it. Maybe bending the restpoint of the throttle handle a bit (as suggested) may help.
set for the RS (with LFW) modified 964's have the standard mapping (for a dual mass FW) so
stalling can sometimes happen. I have the RS clutch kit and when I stop the revs drop to about 100 and then the ECU searches the right timing/mixture and finds it at about 800 revs... 'but sometims it stalls..
I can live with it. Maybe bending the restpoint of the throttle handle a bit (as suggested) may help.
12-23-2010, 03:51 PM
#19
checking for intake air leaks and getting access to a hammer is the current plan - unless there are any more suggestions from the RL team here!
12-26-2010, 04:45 AM
#21
Drifting
It's not the idle itself that's the stalling issue. The difference between a RS and a stock car is that the fuel "pick up point " is set a bit higher in the RS. When you lift off from throttle the fuel is shut off until the revs are just above the idle point. With the LWF/stock DME the revs are falling to quickly and too near the idle point so the DME doesn't have the time to pick up the revs with the result that the revs just "falls through" and the engine stalls. This is way a "manual fix" is to blip the throttle when the revs are falling, in order to give the DME some more time.
So when you get a modified chip for a LWF it's not the idle that's adjusted, it should be the pick up point that should be set higher.
Thomas
So when you get a modified chip for a LWF it's not the idle that's adjusted, it should be the pick up point that should be set higher.
Thomas
04-21-2011, 05:52 AM
#22
Quick update because I have solved my problem.
I think I have read every thread on 964 idle problems.
There were 1 or 2 people that said their car never idles correctly until a Bosch Hammer system adaptation.
The majority said that the battery disconnection technique was the same as the Bosch Hammer system adaptation.
To try to resolve the idle dipping (I may or may not have a LWF), I have tried:
- new ISV
- Steve Wong chip
- new coils
- new fuel filler neck & cap
- checked for vacuum leaks
- new air filter
- cleaned AFM
- fuel injector cleaner fuel additive
- new oxygen sensor
I have tried the battery disconnection technique 20 or 30 times ... when cold, when hot, idling for 10mins, blasting for 10 mins.
The car continued to have an idle dip .. when the revs dropped.
Today I drove to the mechanic with the usual minor slight idle dipping.
Bosch Hammer system adaptation.
I drove home without idle dipping.
My conclusion is that the DME reset with the battery disconnection technique is very different to the Bosch Hammer system adaptation.
I think I have read every thread on 964 idle problems.
There were 1 or 2 people that said their car never idles correctly until a Bosch Hammer system adaptation.
The majority said that the battery disconnection technique was the same as the Bosch Hammer system adaptation.
To try to resolve the idle dipping (I may or may not have a LWF), I have tried:
- new ISV
- Steve Wong chip
- new coils
- new fuel filler neck & cap
- checked for vacuum leaks
- new air filter
- cleaned AFM
- fuel injector cleaner fuel additive
- new oxygen sensor
I have tried the battery disconnection technique 20 or 30 times ... when cold, when hot, idling for 10mins, blasting for 10 mins.
The car continued to have an idle dip .. when the revs dropped.
Today I drove to the mechanic with the usual minor slight idle dipping.
Bosch Hammer system adaptation.
I drove home without idle dipping.
My conclusion is that the DME reset with the battery disconnection technique is very different to the Bosch Hammer system adaptation.
04-21-2011, 10:00 AM
#23
Yes, they are different:
Code:
Idle Adaptation
"What exactly is a 'system adaptation', and how is this different from a
battery disconnect reset of the DME?"
The 964 DME ECM has two adaptations:
1. Idle Adaptation -
On the earlier 3.2 DME system the idle was set by an external jumper
(caused open-loop idle) & then the idle screw was set to "center"
the idle RPM. On the 964, the Hammer causes the DME to go open-loop
and then causes the DME to "step" to the center for 880 RPMs. This
results in the closed-loop idle being "centered" for full
regulation.
2. CO adaptation -
The 964 DME ECM goes thru a CO adaptation whereby it runs open-loop
without the O2 sensor to "center" the CO setting to allow for small
variable changes, e.g. air leaks, fuel pressure, so in the
closed-loop mode the O2 system has optimal range (similar to TRA in
OBDII).
Both of the adaptation values are "lost" if the constant battery
voltage (pin 18) is removed. #1 above requires use of the Hammer. #2
occurs at initial running after battery voltage "loss".
"What happens with the idle in the case of a battery disconnect and no
hammer adaptation?"
The closed-loop still maintains the target idle of 880 RPMs but it's not
optimized for load changes, e.g. the A.C. compressor, the fans, the
lights, and the adapted CO setting.
04-21-2011, 10:48 AM
#24
Yes, but this statement seems to suggest that it is the same if you don't put any load on the system .... "The closed-loop still maintains the target idle of 880 RPMs but it's not optimized for load changes."
I never used any loads before or after and there was a big difference with a hammer adaptation so the statement is not correct. ie the hammer adaptation is more than just optimising for load changes.
I never used any loads before or after and there was a big difference with a hammer adaptation so the statement is not correct. ie the hammer adaptation is more than just optimising for load changes.
04-21-2011, 06:39 PM
#25
Nordschleife Master
I regularly disconnect the battery on my C2 and have never had to get hold of a Hammer for idle adaption. So the only conclusion I can draw is that some 964s need it and some don't.
04-21-2011, 07:13 PM
#26
04-22-2011, 06:33 AM
#27
Nordschleife Master
AH! I'd already forgot that I'd suggested C4s were a bit more difficult to adapt and (for some reason) always thought you had a C2....don't worry it's my age and forget things more easily now 
