Car Dies when accelerating - More frequent after a cold start.
11-28-2011, 08:37 PM
#31
Racer
Thread Starter
Join Date: Apr 2008
Location: Lexington, Kentucky
Posts: 486
Likes: 0
Received 0 Likes
on
0 Posts
It is continuing to die intermittently after replacing the coolant temp sensor. I have decided to bring it in and have it looked at by a more experienced mechanic. Dropped it off this evening and his impression based on my explanation of what was happening is that it might be the cycling valve (unlikely but possible) or it could be a bad DME or KLR. He has a spare DME so that should be easy to check. I will update when I know more.
01-12-2012, 03:13 PM
#32
Racer
Thread Starter
Join Date: Apr 2008
Location: Lexington, Kentucky
Posts: 486
Likes: 0
Received 0 Likes
on
0 Posts
Stuttgart Motors has the car now. Dan is a well respected Porsche mechanic in this area. Not sure if I can translate what he said exactly, but I will try. Any errors in logic will be mine and not Dan's at Stuttgart.
At this point Dan is certain that the cut off is electronic. He has swapped the ECU with no change in results. He has determined that when it cuts off, if you keep your foot on the throttle and quickly turn the key off and on (not start position, just back to on), the car will immediately run properly again.
He doesn't think it is cutting fuel as it quits abruptly. It feels like over boost protection. However the fact that the key needs to be cycled off and on is confusing. Dan is currently trying to source a local KLR computer to swap to see if that changes how it behaves.
My question is what could cause the car to die and be reset by the ignition switch? Is it only the KLR or could there be some other explanation?
Also, if anyone has a KLR I could borrow with stock chips, let me know. If my mechanic is not able to source one locally, it might be helpful. Not ready to give up on finding one locally, but I would like to know my options.
Michael
At this point Dan is certain that the cut off is electronic. He has swapped the ECU with no change in results. He has determined that when it cuts off, if you keep your foot on the throttle and quickly turn the key off and on (not start position, just back to on), the car will immediately run properly again.
He doesn't think it is cutting fuel as it quits abruptly. It feels like over boost protection. However the fact that the key needs to be cycled off and on is confusing. Dan is currently trying to source a local KLR computer to swap to see if that changes how it behaves.
My question is what could cause the car to die and be reset by the ignition switch? Is it only the KLR or could there be some other explanation?
Also, if anyone has a KLR I could borrow with stock chips, let me know. If my mechanic is not able to source one locally, it might be helpful. Not ready to give up on finding one locally, but I would like to know my options.
Michael
01-12-2012, 03:36 PM
#33
Racer
Thread Starter
Join Date: Apr 2008
Location: Lexington, Kentucky
Posts: 486
Likes: 0
Received 0 Likes
on
0 Posts
Just saw this on clarks-garage....
6.8 Random Boost Fall Problem.
Statement: I own a 1986 944 Turbo that I bought with 71K miles. Shortly after buying the car I began experiencing problems with the turbo boosting. It will happen randomly and always at a bad time. The problem consists of the turbo only boosting to 1.2 bar rather than the usual 1.8 bar. This becomes extremely annoying while trying to pass on a country road. The problem cures itself when the engine is shut off and immediately started again. I have tried shutting it down and starting several times while coasting into toll booths and I have never had a problem after the restart. About seven months ago I took the car to a Porsche Dealer. The mechanics worked on the car for two hours, which included a few calls to other dealerships. Unfortunately, they could not find the problem. Also has a rough cold idle.
Diagnosis 1: To really nail this down, one would want to do a complete checkout of your exhaust system, consider removing the turbocharger and re-gasket it, and evaluate the waste gate. Putting it on a dyno could help, too, because you could evaluate the exhaust gases at the same time. One reason for the loss of boost can be lack of fuel - leaning - which would be picked up by the sniffer. If fuel were the problem, it could be related to failing fuel pressure regulators on the fuel rail, or a vacuum leak which would compromise the effectiveness of the fuel enrichment system. The frustrating part of this sort of thing is that it is still intermittent, and probably did not show itself to the shop you took it to.
Diagnosis 2: Your problem could be a bad throttle position sensor. The fact that the problem goes away after restart would tend to confirm it. My 87 951 had the same problem early in its life.
Solution: The problem turned out to be the KLR chip.
Can anyone explain what it means by the restart would confirm a problem with the TPS? Is it possible that I just need a new stock KLR chip and not a whole KLR unit?
6.8 Random Boost Fall Problem.
Statement: I own a 1986 944 Turbo that I bought with 71K miles. Shortly after buying the car I began experiencing problems with the turbo boosting. It will happen randomly and always at a bad time. The problem consists of the turbo only boosting to 1.2 bar rather than the usual 1.8 bar. This becomes extremely annoying while trying to pass on a country road. The problem cures itself when the engine is shut off and immediately started again. I have tried shutting it down and starting several times while coasting into toll booths and I have never had a problem after the restart. About seven months ago I took the car to a Porsche Dealer. The mechanics worked on the car for two hours, which included a few calls to other dealerships. Unfortunately, they could not find the problem. Also has a rough cold idle.
Diagnosis 1: To really nail this down, one would want to do a complete checkout of your exhaust system, consider removing the turbocharger and re-gasket it, and evaluate the waste gate. Putting it on a dyno could help, too, because you could evaluate the exhaust gases at the same time. One reason for the loss of boost can be lack of fuel - leaning - which would be picked up by the sniffer. If fuel were the problem, it could be related to failing fuel pressure regulators on the fuel rail, or a vacuum leak which would compromise the effectiveness of the fuel enrichment system. The frustrating part of this sort of thing is that it is still intermittent, and probably did not show itself to the shop you took it to.
Diagnosis 2: Your problem could be a bad throttle position sensor. The fact that the problem goes away after restart would tend to confirm it. My 87 951 had the same problem early in its life.
Solution: The problem turned out to be the KLR chip.
Can anyone explain what it means by the restart would confirm a problem with the TPS? Is it possible that I just need a new stock KLR chip and not a whole KLR unit?
Last edited by Ky944TurboNewbie; 01-12-2012 at 03:38 PM. Reason: additional question
02-06-2012, 06:39 PM
#34
Racer
Thread Starter
Join Date: Apr 2008
Location: Lexington, Kentucky
Posts: 486
Likes: 0
Received 0 Likes
on
0 Posts
Update.....
I have tried a new DME Computer with no change. I have tried a new KLR computer with worse results. Car acts the same but cuts out almost immediately with just a little acceleration.
I have learned that the problem can be created consistently when boosting at a little higher rpm's. When running under boost, it will cut out consistently at about 4000 rpm's. It is possible to feather the gas a little and keep it running somewhat. When the key is switched off and on, all is reset and works great again until about 4000 rpm's again.
I am suspecting a boost leak at this point from reading some other threads. Any thoughts would be appreciated.
I have tried a new DME Computer with no change. I have tried a new KLR computer with worse results. Car acts the same but cuts out almost immediately with just a little acceleration.
I have learned that the problem can be created consistently when boosting at a little higher rpm's. When running under boost, it will cut out consistently at about 4000 rpm's. It is possible to feather the gas a little and keep it running somewhat. When the key is switched off and on, all is reset and works great again until about 4000 rpm's again.
I am suspecting a boost leak at this point from reading some other threads. Any thoughts would be appreciated.
