New 964 owner performance problem, help
Thread Starter
Track Day
Joined: Feb 2002
Posts: 17
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From: San Jose Ca
New 964 owner performance problem, help
Hi,
My first post and I am a new owner. I purchased a 1990 964 C2 with 42K miles her in the San Jose area. It is my wifes daily driver. Known modifications to the car are LWF and autothority chip. The car has minimal stalling problems although it does happen occaisionally. It lacks the distributor modification.
The problem that concerns me is a kind of a pause in acceleration near 4500RPM. Would be a dip on a dyno chart. I cannot seem to pinpoint the start of the dip. Sometimes it seems like it is as low as 3750 or 4000. It is worst at 4500 and by 4750 the car always seems to be pulling hard and it pulls hard to redline.
The dip is so significant that it feels as if the car has run out of gasoline. The front end dives as weight is transferred forward. That it then pulls hard to redline makes me think it is not a fuel flow problem (injectors or filter). I plan to reset the DME in hopes that that will help and to try running 1/2 race fuel. I will also verify that both distributors are functioning.
I was hoping that somone knew if 4500 was some important RPM (transfer from closed loop to open loop? change in valve timing? (does 964 have this?) RPM most likely to knock causing retardation of timging?)
Or any other advice. I have not worked on this car but do alot of work on my 99 M3 (easier with the obdII).
My first post and I am a new owner. I purchased a 1990 964 C2 with 42K miles her in the San Jose area. It is my wifes daily driver. Known modifications to the car are LWF and autothority chip. The car has minimal stalling problems although it does happen occaisionally. It lacks the distributor modification.
The problem that concerns me is a kind of a pause in acceleration near 4500RPM. Would be a dip on a dyno chart. I cannot seem to pinpoint the start of the dip. Sometimes it seems like it is as low as 3750 or 4000. It is worst at 4500 and by 4750 the car always seems to be pulling hard and it pulls hard to redline.
The dip is so significant that it feels as if the car has run out of gasoline. The front end dives as weight is transferred forward. That it then pulls hard to redline makes me think it is not a fuel flow problem (injectors or filter). I plan to reset the DME in hopes that that will help and to try running 1/2 race fuel. I will also verify that both distributors are functioning.
I was hoping that somone knew if 4500 was some important RPM (transfer from closed loop to open loop? change in valve timing? (does 964 have this?) RPM most likely to knock causing retardation of timging?)
Or any other advice. I have not worked on this car but do alot of work on my 99 M3 (easier with the obdII).
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From: San Jose, CA
Flatline,
Welcome to the Rennlist! Sorry to hear about your problem, though.
I was wondering a couple of things:
1. Have you seen the proposed dyno chart for the Autothority chip? Is there any changes around 4500 RPM.
2. Do you have the stock chip? I was wondering if if would affect the performance if you switched it in.
3. Does the "jolt" happen EVERY time you get around 4500 rpm, or is it intermittent?
4. Any other symptoms -- warning lights, stalling, etc? Do you get a sulfur smell after the "jolt" happens?
5. Have you switched out the DME relay? This is a common culprit.
6. Has anyone checked the condition of the distributor belt? The symptoms of a failing belt include violent missing, but when mine failed, it missed all the time, not just at 4500 rpm.
7. When was the last time the car was serviced? Were the spark plugs changed? How about the spark plug wires?
I had an intermittent problem with power loss/back on -- so violent that once I launched a cup of coffee in the car, and this was at low speed. (I know, I shouldn't drink & drive.) It usually happened at freeway speeds, though. Anyway, it turned out to be a cracked spark plug boot.
Another long shot is that the grounding strap on the left hinge of the engine lid might be coming into contact with the second ignition's coil wire. Porsche had a Tech Bulletin out that you should move the grounding strap to the side of the hinge.
Oh, and if you are interested in good mechanics in the area, let me know.
-- Melissa
Welcome to the Rennlist! Sorry to hear about your problem, though.
I was wondering a couple of things:
1. Have you seen the proposed dyno chart for the Autothority chip? Is there any changes around 4500 RPM.
2. Do you have the stock chip? I was wondering if if would affect the performance if you switched it in.
3. Does the "jolt" happen EVERY time you get around 4500 rpm, or is it intermittent?
4. Any other symptoms -- warning lights, stalling, etc? Do you get a sulfur smell after the "jolt" happens?
5. Have you switched out the DME relay? This is a common culprit.
6. Has anyone checked the condition of the distributor belt? The symptoms of a failing belt include violent missing, but when mine failed, it missed all the time, not just at 4500 rpm.
7. When was the last time the car was serviced? Were the spark plugs changed? How about the spark plug wires?
I had an intermittent problem with power loss/back on -- so violent that once I launched a cup of coffee in the car, and this was at low speed. (I know, I shouldn't drink & drive.) It usually happened at freeway speeds, though. Anyway, it turned out to be a cracked spark plug boot.
Another long shot is that the grounding strap on the left hinge of the engine lid might be coming into contact with the second ignition's coil wire. Porsche had a Tech Bulletin out that you should move the grounding strap to the side of the hinge.
Oh, and if you are interested in good mechanics in the area, let me know.
-- Melissa
Thread Starter
Track Day
Joined: Feb 2002
Posts: 17
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From: San Jose Ca
Great detailed reply. Thanks.
Questions restated with replies:
1. Have you seen the proposed dyno chart for the Autothority chip? Is there any changes around 4500 RPM.
Where would I find a proposed dyno chart? I did not see one with the doccumentation I received from the previous owner. I have had poor luck finding any information Autothority's website
2. Do you have the stock chip? I was wondering if if would affect the performance if you switched it in.
I do have the stock chip. I was also considering swapping it in until I discovered it requred an R&R of the drivers seat. One of my first thoughts was that the chip was tuned for more better gasoline than the 91 octane (maybe) gas we can get around here. Hence my plan to try race gas. Chip R&R remains a backup plan.
3. Does the "jolt" happen EVERY time you get around 4500 rpm, or is it intermittent?\
There are times when it is more subtle than others. As it is my wifes daily driver I haven't had enough seat time to correlate it with anything . I have not noticed a strong correlation with temperature. On any given day it seems that every acceleration shows the same effect. It seems worst in second gear after a first gear shift near redline although under these conditions it is hard to note RPMs.
4. Any other symptoms -- warning lights, stalling, etc? Do you get a sulfur smell after the "jolt" happens?
The car occaisionally stalls when decelerating and putting in the clutch. It has happened to me 2x (in several hundred miles) but my wife says it happens a few times a week. I have once or twice noticed a sulfer smell but have not noticed it to be correlated with the jolt. I will look for this.
5. Have you switched out the DME relay? This is a common culprit.
The DME relay was replaced the first week and cleared up alot of idle problems although the idle still bounces alot at cold.
6. Has anyone checked the condition of the distributor belt? The symptoms of a failing belt include violent missing, but when mine failed, it missed all the time, not just at 4500 rpm.
This is on my list. It does seem odd though that it would effect it so adversely at 4500 and then pull strong (much more so than my M3) to redline.
7. When was the last time the car was serviced? Were the spark plugs changed? How about the spark plug wires?
Had 60K service done (at 42K) spark plugs were replaced. Wires were stated to be in good condition. Plugs appeared in good condition and color.
It does occur to me that the "jolt" was either less obvious before the service or did not exist. I certainly noted that the midrange torque was not the same as my M3 but had not noticed this abrupt loss of power. Either the power before 4000 and after 4750 improved after the service or the problem surfaced since then. I also did not notice the problem when I picked up the car and drove away spiritedly
Service was done by Ken's Sportech.
Questions restated with replies:
1. Have you seen the proposed dyno chart for the Autothority chip? Is there any changes around 4500 RPM.
Where would I find a proposed dyno chart? I did not see one with the doccumentation I received from the previous owner. I have had poor luck finding any information Autothority's website
2. Do you have the stock chip? I was wondering if if would affect the performance if you switched it in.
I do have the stock chip. I was also considering swapping it in until I discovered it requred an R&R of the drivers seat. One of my first thoughts was that the chip was tuned for more better gasoline than the 91 octane (maybe) gas we can get around here. Hence my plan to try race gas. Chip R&R remains a backup plan.
3. Does the "jolt" happen EVERY time you get around 4500 rpm, or is it intermittent?\
There are times when it is more subtle than others. As it is my wifes daily driver I haven't had enough seat time to correlate it with anything . I have not noticed a strong correlation with temperature. On any given day it seems that every acceleration shows the same effect. It seems worst in second gear after a first gear shift near redline although under these conditions it is hard to note RPMs.
4. Any other symptoms -- warning lights, stalling, etc? Do you get a sulfur smell after the "jolt" happens?
The car occaisionally stalls when decelerating and putting in the clutch. It has happened to me 2x (in several hundred miles) but my wife says it happens a few times a week. I have once or twice noticed a sulfer smell but have not noticed it to be correlated with the jolt. I will look for this.
5. Have you switched out the DME relay? This is a common culprit.
The DME relay was replaced the first week and cleared up alot of idle problems although the idle still bounces alot at cold.
6. Has anyone checked the condition of the distributor belt? The symptoms of a failing belt include violent missing, but when mine failed, it missed all the time, not just at 4500 rpm.
This is on my list. It does seem odd though that it would effect it so adversely at 4500 and then pull strong (much more so than my M3) to redline.
7. When was the last time the car was serviced? Were the spark plugs changed? How about the spark plug wires?
Had 60K service done (at 42K) spark plugs were replaced. Wires were stated to be in good condition. Plugs appeared in good condition and color.
It does occur to me that the "jolt" was either less obvious before the service or did not exist. I certainly noted that the midrange torque was not the same as my M3 but had not noticed this abrupt loss of power. Either the power before 4000 and after 4750 improved after the service or the problem surfaced since then. I also did not notice the problem when I picked up the car and drove away spiritedly
Service was done by Ken's Sportech.
Racer
Joined: Jan 2002
Posts: 314
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From: P-ville, PA
Ok, here's the deal. I had a light weight flywheel put into my '92 and had some very bad results with the already installed autothority chip. This was a long time ago before there were different versions of the chip avail. It seems that the early chips were not able to keep the engine from dying with the LWF, there are now( I believe) chips around that can compensate for the loss in rotational mass of the LWF. I will say two things, the car with the LWF was lightning fast, triple digits in a heartbeat and the noise from the tranny was downright frightening. If I ever have to drop the engine again I will try the LWF route again, but for now I'm using the LUK.
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From: San Jose, CA
Flatline,
I had thought that the old Automotion catalogs showed dynos of the Autothority chip, but now that I think of it, I'm pretty sure it was for a Weltmeister (sp?) chip.
Interesting point about the 91 octane -- I think the aftermarket chips don't take lower octanes into consideration. I would talk to Autothority to see if that chip would work well with 91 octane, and also to discuss if they have a newer chip that might work better with the LWF.
However, it also sounds like this problem is a recent development. You've probably been running the car on 91 for about a year (I think that's when the switch occurred.)
Have you had Ken's SportTech (or any other shop) do a Bosch Hammer diagnostic on the car to see if it's throwing any codes?
Good luck!
-- Melissa
I had thought that the old Automotion catalogs showed dynos of the Autothority chip, but now that I think of it, I'm pretty sure it was for a Weltmeister (sp?) chip.
Interesting point about the 91 octane -- I think the aftermarket chips don't take lower octanes into consideration. I would talk to Autothority to see if that chip would work well with 91 octane, and also to discuss if they have a newer chip that might work better with the LWF.
However, it also sounds like this problem is a recent development. You've probably been running the car on 91 for about a year (I think that's when the switch occurred.)
Have you had Ken's SportTech (or any other shop) do a Bosch Hammer diagnostic on the car to see if it's throwing any codes?
Good luck!
-- Melissa
Racer
Joined: Jan 2002
Posts: 377
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From: Canada
You don't need to remove the drivers seat to take out the DME. Just move the seat back as much as possible, disconnect the battery and unscrew 4 x bolts (10 mm), snap the wire bracket back and take the DME out. If you don't know how to take the chip out, it can be frustrating, however I can fax you the authority manual if you need it.
Thread Starter
Track Day
Joined: Feb 2002
Posts: 17
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From: San Jose Ca
Improvements!!!!
I reset the DME. At least I think so. I used the 11second accelerator method I found described in another post. Prior I had removed the DME fuse (#35) for 15min. I was trying to avoid removing the battery as I would have to find that stereo code. Can anyone confirm that I really have reset the DME?
I wish I had driven it immediately before the reset. It felt much improved the whole time. There was virtually no lag when shifting at redline. Perhaps lag is no longer the correct description. The only definitive sign of the problem I experienced was when accelerating from 3000rpm in 2cd it almost felt like a turbo kicked in at 5000rpm. But there was not a dip prior to it. Much more drivable.
I would lean towards this being the O2 sensor if anyone could confirm that 5000RPM was when the car went open loop.
I will be gone camping all weekend but will try again on Sunday or Monday. Will update you all then. Thanks for the help.
Cheers,
Eric
I reset the DME. At least I think so. I used the 11second accelerator method I found described in another post. Prior I had removed the DME fuse (#35) for 15min. I was trying to avoid removing the battery as I would have to find that stereo code. Can anyone confirm that I really have reset the DME?
I wish I had driven it immediately before the reset. It felt much improved the whole time. There was virtually no lag when shifting at redline. Perhaps lag is no longer the correct description. The only definitive sign of the problem I experienced was when accelerating from 3000rpm in 2cd it almost felt like a turbo kicked in at 5000rpm. But there was not a dip prior to it. Much more drivable.
I would lean towards this being the O2 sensor if anyone could confirm that 5000RPM was when the car went open loop.
I will be gone camping all weekend but will try again on Sunday or Monday. Will update you all then. Thanks for the help.
Cheers,
Eric
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Thread Starter
Track Day
Joined: Feb 2002
Posts: 17
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From: San Jose Ca
Sorry to follow my own post. I went ahead and did a distributor belt check. I removed the primary distributor center plug. With it removed the car stalls and cannot be restarted. Looks like I need to remove the second cap to make sure. Wonder if it's worth removing the second primary connection until everything is verified/fixed.
Cheers,
Eric
Cheers,
Eric
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Flatline:
With an unmodified car, disconnecting the primary distributor lead should have no effect on the car at idle if everything is OK. The dual ignition is used to allow the engine to burn fuel more completely under load, hence allowing the car to use a higher compression ratio without having as much knock AND use lower octane fuels.
You need to pop the distributor off and see if the belt is OK. Until you do this I would not drive the car hard at all. If the belt is fried, you might want to (as you suggested) pull the second lead off and see if you're still getting the 4500RPM problems. A simple check beats the hell out of an overhaul, even if it is a PIA.
The distributor belt problems and symptoms should be in the archives in enormous detail if you need more info (including re-building sources for less money!).
With an unmodified car, disconnecting the primary distributor lead should have no effect on the car at idle if everything is OK. The dual ignition is used to allow the engine to burn fuel more completely under load, hence allowing the car to use a higher compression ratio without having as much knock AND use lower octane fuels.
You need to pop the distributor off and see if the belt is OK. Until you do this I would not drive the car hard at all. If the belt is fried, you might want to (as you suggested) pull the second lead off and see if you're still getting the 4500RPM problems. A simple check beats the hell out of an overhaul, even if it is a PIA.
The distributor belt problems and symptoms should be in the archives in enormous detail if you need more info (including re-building sources for less money!).
Race Car
Joined: Aug 2001
Posts: 4,922
Likes: 1
From: London, UK
[quote]Originally posted by 91C2wrencher:
<strong>Ok, here's the deal. I had a light weight flywheel put into my '92 and had some very bad results with the already installed autothority chip. This was a long time ago before there were different versions of the chip avail. It seems that the early chips were not able to keep the engine from dying with the LWF, there are now( I believe) chips around that can compensate for the loss in rotational mass of the LWF. I will say two things, the car with the LWF was lightning fast, triple digits in a heartbeat and the noise from the tranny was downright frightening. If I ever have to drop the engine again I will try the LWF route again, but for now I'm using the LUK.</strong><hr></blockquote>
Can anyone explain why the LWF cars are 'lightning fast' (according to their owners) when this conversion does not ( I believe)increase power or torque?
Thanks!
<strong>Ok, here's the deal. I had a light weight flywheel put into my '92 and had some very bad results with the already installed autothority chip. This was a long time ago before there were different versions of the chip avail. It seems that the early chips were not able to keep the engine from dying with the LWF, there are now( I believe) chips around that can compensate for the loss in rotational mass of the LWF. I will say two things, the car with the LWF was lightning fast, triple digits in a heartbeat and the noise from the tranny was downright frightening. If I ever have to drop the engine again I will try the LWF route again, but for now I'm using the LUK.</strong><hr></blockquote>
Can anyone explain why the LWF cars are 'lightning fast' (according to their owners) when this conversion does not ( I believe)increase power or torque?
Thanks!
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From: Dana Point, CA
Hmmm .... used to have a LWF in my car. Yes, the engine revved faster. But, it couldn't have been that great, because .... after having the LUK DMF installed, I don't miss it. Somewhat subjective, but in my mind, certainly not worth the stalling/idle issues (I cannot tolerate a car that stalls).
I know that tuners such as Autothority are purportedly making chips that will cure the idle issues. However, based on what I've read on this board, these chips do not appear to be as effective as promised. That is, several people have purchased LWFs with a custom tuned chip, and still have idle problems. Certainly makes installing a LWF in a pre-96 964/993 a risky proposition ... one that requires careful thought.
Now, I haven't read of any 96+ (OBDII) 911 owners that have had idle problems after installing a LWF. Apparently, the ECU's software handles the LWF much better. Considering that I have a '97 OBDII engine, I will give a LWF serious (re)consideration if my (65k miles) LUK ever gives out.
If I still had a 964 based engine, and wanted a LWF, I would go with Andial's semi-LWF. Not as drastic as an RS LWF, but still much lighter than stock. Better yet, I believe Andial when they say there are no idle issues with their semi-LWF. In particular, I know of one '95 993 owner that couldn't get rid of LWF-induced idle problems until he had the Andial unit installed.
I know that tuners such as Autothority are purportedly making chips that will cure the idle issues. However, based on what I've read on this board, these chips do not appear to be as effective as promised. That is, several people have purchased LWFs with a custom tuned chip, and still have idle problems. Certainly makes installing a LWF in a pre-96 964/993 a risky proposition ... one that requires careful thought.
Now, I haven't read of any 96+ (OBDII) 911 owners that have had idle problems after installing a LWF. Apparently, the ECU's software handles the LWF much better. Considering that I have a '97 OBDII engine, I will give a LWF serious (re)consideration if my (65k miles) LUK ever gives out.
If I still had a 964 based engine, and wanted a LWF, I would go with Andial's semi-LWF. Not as drastic as an RS LWF, but still much lighter than stock. Better yet, I believe Andial when they say there are no idle issues with their semi-LWF. In particular, I know of one '95 993 owner that couldn't get rid of LWF-induced idle problems until he had the Andial unit installed.
Race Car
Joined: Aug 2001
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From: London, UK
[quote]Originally posted by jonfkaminsky:
<strong>less rotating mass to spin up. Reducing the rotational inertia the engine/driveline components must deal with is, pound-for-pound, many times more effective in decreasing acceleration time than reducing the weight of the car itself.</strong><hr></blockquote>
Your logic sounds ok but how is it that it doesn't produce more power? If it doesn't produce more HP or torque how can it possibly make the car accelerate faster?
My feeling is that if your inertia theory is correct then you would for example lose revs more easily when hitting an incline on the motorway for example - something which to means that you have less torque......
What is the differenc ein mass of the LWF/DMF? How does this compare as a percentage of the total mass being moved?
<strong>less rotating mass to spin up. Reducing the rotational inertia the engine/driveline components must deal with is, pound-for-pound, many times more effective in decreasing acceleration time than reducing the weight of the car itself.</strong><hr></blockquote>
Your logic sounds ok but how is it that it doesn't produce more power? If it doesn't produce more HP or torque how can it possibly make the car accelerate faster?
My feeling is that if your inertia theory is correct then you would for example lose revs more easily when hitting an incline on the motorway for example - something which to means that you have less torque......
What is the differenc ein mass of the LWF/DMF? How does this compare as a percentage of the total mass being moved?
Racer
Joined: Aug 2001
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From: UK
The LWF makes a big difference to the engine's ability to accelerate when the clutch is disengaged, because then the reduction in moment of inertia is significant - so it helps make snappier heel and toe downshifts. When the clutch is engaged the reduction in crankshaft moment of inertia is tiny compared to accelerating the mass of the car, not enough to make a measurable difference to acceleration.
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From: London, UK
JohnM
This is the way I see it too. The only reason I bring this up is so that newer owners don't run out and spend $$$$ on the conversion when it makes FA difference to performance and may introduce stalling problems. All because someone stated their car was 'lightning fast'....I am not intending to start an argument - just keeping the facts as straight as possible.
Christer
This is the way I see it too. The only reason I bring this up is so that newer owners don't run out and spend $$$$ on the conversion when it makes FA difference to performance and may introduce stalling problems. All because someone stated their car was 'lightning fast'....I am not intending to start an argument - just keeping the facts as straight as possible.
Christer
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From: Dana Point, CA
Well, we know LWFs provide some sort of performance advantage--however subtle--as they're common race car fare. Most likely the "snappier heel and toe downshifts" John mentions. Regardless, as I've implied above, I'm not sure that any mod that causes your engine to stall--even infrequently--is fit for the street.