Continued problem(power loss downhill)
09-02-2005, 12:06 AM
#1
Burning Brakes
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Continued problem(power loss downhill)
I am still having this problem and have yet to figure it out. I will reference the previous thread.
https://rennlist.com/forums/964-forum/191857-power-loss-downhill.html
I recently did some work I had hoped would fix the problem, but it didn't.
Here's what I did.
-Cleaned intakes (I also smoothed out and rough-polished the inside of the Al runners. No hogging really just smoothed)
-Cleaned plastic stacks especially injector seal areas.
-Had injectors cleaned (Thanks to cruizin) and tested.
-Replaced all the rubber connectors between the rubber stacks and the Al runners.
-Replaced the rectangular seals under the plastic stacks.
-Cleaned the resonance tube. There was a bit of sludge under the butterfly. It should be working better now.
The only thing what I did seems to have done is make the idle a bit more definite(instantly to the right rpm and steady) on start. To tell the truth I'm rather bummed about it. Since the problem goes away when you trigger WOT I figured it could be a vacuum leak. Still could of course, there are a lot of hoses back there. The only thing I know of to try (besides getting it hammered) is testing the AFM again while its hooked to the car (checking for a smooth and steady V change as you open the flap unless someone has a better suggestion).
Does anyone have any further thoughts? Adrian suggested I check it with a hammer for possible sensor failure. Thats certainly not out of the realm of possibilities. I did check the basic functions of the sensors at different temps and they seemed to be in spec, but that doesnt mean much. There is a shop locally who will pull the codes for me for a fee.
https://rennlist.com/forums/964-forum/191857-power-loss-downhill.html
I recently did some work I had hoped would fix the problem, but it didn't.
Here's what I did.
-Cleaned intakes (I also smoothed out and rough-polished the inside of the Al runners. No hogging really just smoothed)
-Cleaned plastic stacks especially injector seal areas.
-Had injectors cleaned (Thanks to cruizin) and tested.
-Replaced all the rubber connectors between the rubber stacks and the Al runners.
-Replaced the rectangular seals under the plastic stacks.
-Cleaned the resonance tube. There was a bit of sludge under the butterfly. It should be working better now.
The only thing what I did seems to have done is make the idle a bit more definite(instantly to the right rpm and steady) on start. To tell the truth I'm rather bummed about it. Since the problem goes away when you trigger WOT I figured it could be a vacuum leak. Still could of course, there are a lot of hoses back there. The only thing I know of to try (besides getting it hammered) is testing the AFM again while its hooked to the car (checking for a smooth and steady V change as you open the flap unless someone has a better suggestion).
Does anyone have any further thoughts? Adrian suggested I check it with a hammer for possible sensor failure. Thats certainly not out of the realm of possibilities. I did check the basic functions of the sensors at different temps and they seemed to be in spec, but that doesnt mean much. There is a shop locally who will pull the codes for me for a fee.
09-02-2005, 03:02 AM
#2
Instructor
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Heirsh,
Given that you tried multiple things and the problem still exists, I would go back to Adrian's suggestion about the culprit being something mechanical.
This is what I found when I faced a similar problem:
https://rennlist.com/forums/964-forum/114913-troubleshooting-for-stalling-hesitation-long.html
Good luck in fixing this annoying problem...
Given that you tried multiple things and the problem still exists, I would go back to Adrian's suggestion about the culprit being something mechanical.
This is what I found when I faced a similar problem:
https://rennlist.com/forums/964-forum/114913-troubleshooting-for-stalling-hesitation-long.html
Good luck in fixing this annoying problem...
09-02-2005, 04:22 AM
#3
Track Day
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Heirsh,
Try unplugging the 02 sensor, then go for a drive to see if there is an improvement. My C2 was losing power while travelling downhill which went away after unplugging the 02 sensor. So I replaced it and that problem went away.
Good luck,
Gary
Try unplugging the 02 sensor, then go for a drive to see if there is an improvement. My C2 was losing power while travelling downhill which went away after unplugging the 02 sensor. So I replaced it and that problem went away.
Good luck,
Gary
09-02-2005, 09:25 AM
#4
Burning Brakes
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o2 sensor is new, but that is a good test nonetheless.
It could still be something mechanical of course (since I don't know what it is) but if it was then why would it clear up when the wot switch is triggered (thus setting the enrichment back to a predesigned full power map)?
arg, this is driving me nuts.
maybe one of these days I'll figure it out.
It could still be something mechanical of course (since I don't know what it is) but if it was then why would it clear up when the wot switch is triggered (thus setting the enrichment back to a predesigned full power map)?
arg, this is driving me nuts.
maybe one of these days I'll figure it out.
09-02-2005, 04:13 PM
#5
Instructor
Your post is timely, as I have the exact same problem. I live in an area that is flat but with many bridges. When I travel down hill on a bridge, the car seems to stall or act like it is out of gas. I suspected the culprits listed in the other post: fuel pickup, filter, etc. But I guess that is not it...
I am curious to see what it turns out to be. I am also willing to do any tests you can think of.
I am curious to see what it turns out to be. I am also willing to do any tests you can think of.
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09-02-2005, 08:26 PM
#11
Instructor
Mine just seems to be "stumbling". I feel that if I put in the clutch it might actually stall.
What do you mean by a more stable idle? Mine seems to go up and down slightly, say 50 +/- rpm.
What do you mean by a more stable idle? Mine seems to go up and down slightly, say 50 +/- rpm.
09-03-2005, 12:25 PM
#12
Three Wheelin'
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Heirsh,
If you have your foot of the gas so the car is driving the motor ,if the revs are high enough, the DME is running in " overrun fuel shut off mode " - no injector drive.This is a common emmisions/economy system used in Motronic.
The DME turns the injectors back on when the revs get down towards idle.
Sounds like the problem is related to the DME getting back to driving the injectors enough to make the car feel OK.
I would double check the throttle idle switch for basic operation and look at throttle position when it opens-does it stay on too long ?
Hope this makes sense as I had a good night out last night !!!!!!!
Geoff
If you have your foot of the gas so the car is driving the motor ,if the revs are high enough, the DME is running in " overrun fuel shut off mode " - no injector drive.This is a common emmisions/economy system used in Motronic.
The DME turns the injectors back on when the revs get down towards idle.
Sounds like the problem is related to the DME getting back to driving the injectors enough to make the car feel OK.
I would double check the throttle idle switch for basic operation and look at throttle position when it opens-does it stay on too long ?
Hope this makes sense as I had a good night out last night !!!!!!!
Geoff
09-05-2005, 10:18 PM
#13
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Hi guys
Add another 964 to the list of those with this problem. Mine is a 1991 C2 Tip and currently in NZ. I've owned it for about 4 months now since trading back from a 993 2S. In every other respect I'm loving having the feel back of the 964 but this downhill thing is bugging me!
I stumbled on the previous threads which got me thinking that yes it only seems to happen when the tank is less than half full. For me it happens worst when just cresting the Auckland Harbour Bridge - typically just coasting over top with about 2,000 revs and gentle acceleration. Stutters and stumbles then picks up with a good heavy foot.
I'm not as technically minded as some here so for now I can't offer any new suggestions but will discuss with my mechnic next time in the shop and see if he's seen it before. Seems to be a pretty widespread problem though so I'm sure a definitive fix will one day be appreciated!
Cheers
Pete
Add another 964 to the list of those with this problem. Mine is a 1991 C2 Tip and currently in NZ. I've owned it for about 4 months now since trading back from a 993 2S. In every other respect I'm loving having the feel back of the 964 but this downhill thing is bugging me!
I stumbled on the previous threads which got me thinking that yes it only seems to happen when the tank is less than half full. For me it happens worst when just cresting the Auckland Harbour Bridge - typically just coasting over top with about 2,000 revs and gentle acceleration. Stutters and stumbles then picks up with a good heavy foot.
I'm not as technically minded as some here so for now I can't offer any new suggestions but will discuss with my mechnic next time in the shop and see if he's seen it before. Seems to be a pretty widespread problem though so I'm sure a definitive fix will one day be appreciated!
Cheers
Pete