Very strange problem, can you help?
01-21-2014 | 05:11 PM
#1
Thread Starter
Track Day
Joined: Nov 2013
Posts: 18
Likes: 0
Very strange problem, can you help?
So, I’ve read and searched all of the threads and have not come across an issue like mine. I was recommended to this site, hoping you are 944 experts.
It all started when a friend gave me an ’86 944 N/A. It was pretty much worn out and finally the clutch came apart making it un-drivable. So, I swapped it out to be turbo model. See my post here;
http://www.944online.com/cgi-bin/for...num=1377294100
It runs really good except for when it goes into this “mode”, but it doesn’t sound like overboost. I have an aftermarket boost gauge and it runs about 11 PSI. It runs great and pulls about 11 PSI boost, then when you let off, it goes into the “mode”.
The “mode”: the car starts and idles perfect, slowly or quickly depress the gas pedal and there is a very hard cliff (cutoff) at 1300 RPM, the tach drops like a rock back to idle. Once back to idle, it picks back up again. Holding the gas pedal down just bounces the tach (rpm) from idle to 1300 RPM. If I rev it up very quickly and get the tach to bounce above 2500 RPM, it picks up and run fine. If I let it drop below 2500 RPM, it drops to idle and comes back up to the 1300 RPM and starts all over again.
If I am driving, I can downshift and get it above 3000 rpm, and it’s fine. When I drive it a while above 2500 rpm for about a mile, it goes back to normal, idles, revs, etc.
If it is idling, I have to “bounce” the tach quickly to get it above 2500, where it will pick up and run fine. If I drive it normally (not really my style), it never goes into the “mode” and just runs perfectly.
Setting overnight, with or without the battery disconnected, it will stay in the mode until I bounce the tach above 2500 rpm, slide the clutch, and drive about a mile.
Disconnecting the TPS temporarily takes it out of this mode, but plugging it back it, goes right back to where it was.
Strange? Hope somebody here can help. This is annoying.
It all started when a friend gave me an ’86 944 N/A. It was pretty much worn out and finally the clutch came apart making it un-drivable. So, I swapped it out to be turbo model. See my post here;
http://www.944online.com/cgi-bin/for...num=1377294100
It runs really good except for when it goes into this “mode”, but it doesn’t sound like overboost. I have an aftermarket boost gauge and it runs about 11 PSI. It runs great and pulls about 11 PSI boost, then when you let off, it goes into the “mode”.
The “mode”: the car starts and idles perfect, slowly or quickly depress the gas pedal and there is a very hard cliff (cutoff) at 1300 RPM, the tach drops like a rock back to idle. Once back to idle, it picks back up again. Holding the gas pedal down just bounces the tach (rpm) from idle to 1300 RPM. If I rev it up very quickly and get the tach to bounce above 2500 RPM, it picks up and run fine. If I let it drop below 2500 RPM, it drops to idle and comes back up to the 1300 RPM and starts all over again.
If I am driving, I can downshift and get it above 3000 rpm, and it’s fine. When I drive it a while above 2500 rpm for about a mile, it goes back to normal, idles, revs, etc.
If it is idling, I have to “bounce” the tach quickly to get it above 2500, where it will pick up and run fine. If I drive it normally (not really my style), it never goes into the “mode” and just runs perfectly.
Setting overnight, with or without the battery disconnected, it will stay in the mode until I bounce the tach above 2500 rpm, slide the clutch, and drive about a mile.
Disconnecting the TPS temporarily takes it out of this mode, but plugging it back it, goes right back to where it was.
Strange? Hope somebody here can help. This is annoying.
01-21-2014 | 05:45 PM
#2
Rennlist Member
Joined: Oct 2002
Posts: 12,008
Likes: 95
From: Hyde Park, NY
Well, it sounds ignition related... I'd start by verifying the solder joints in the DME/KLR are good; verifying the speed an ref sensors are good; verifying the wiring harness is good; verifying the cap and rotor are good; verifying the TPS is good; verifying the AFM is good. It would also be a good idea to verify that there are no vacuum leaks.
01-21-2014 | 09:29 PM
#3
Rennlist Member
Joined: Jun 2007
Posts: 870
Likes: 1
From: San Diego
So, I’ve read and searched all of the threads and have not come across an issue like mine. I was recommended to this site, hoping you are 944 experts.
It all started when a friend gave me an ’86 944 N/A. It was pretty much worn out and finally the clutch came apart making it un-drivable. So, I swapped it out to be turbo model. See my post here;
http://www.944online.com/cgi-bin/for...num=1377294100
It runs really good except for when it goes into this “mode”, but it doesn’t sound like overboost. I have an aftermarket boost gauge and it runs about 11 PSI. It runs great and pulls about 11 PSI boost, then when you let off, it goes into the “mode”.
The “mode”: the car starts and idles perfect, slowly or quickly depress the gas pedal and there is a very hard cliff (cutoff) at 1300 RPM, the tach drops like a rock back to idle. Once back to idle, it picks back up again. Holding the gas pedal down just bounces the tach (rpm) from idle to 1300 RPM. If I rev it up very quickly and get the tach to bounce above 2500 RPM, it picks up and run fine. If I let it drop below 2500 RPM, it drops to idle and comes back up to the 1300 RPM and starts all over again.
If I am driving, I can downshift and get it above 3000 rpm, and it’s fine. When I drive it a while above 2500 rpm for about a mile, it goes back to normal, idles, revs, etc.
If it is idling, I have to “bounce” the tach quickly to get it above 2500, where it will pick up and run fine. If I drive it normally (not really my style), it never goes into the “mode” and just runs perfectly.
Setting overnight, with or without the battery disconnected, it will stay in the mode until I bounce the tach above 2500 rpm, slide the clutch, and drive about a mile.
Disconnecting the TPS temporarily takes it out of this mode, but plugging it back it, goes right back to where it was.
Strange? Hope somebody here can help. This is annoying.
It all started when a friend gave me an ’86 944 N/A. It was pretty much worn out and finally the clutch came apart making it un-drivable. So, I swapped it out to be turbo model. See my post here;
http://www.944online.com/cgi-bin/for...num=1377294100
It runs really good except for when it goes into this “mode”, but it doesn’t sound like overboost. I have an aftermarket boost gauge and it runs about 11 PSI. It runs great and pulls about 11 PSI boost, then when you let off, it goes into the “mode”.
The “mode”: the car starts and idles perfect, slowly or quickly depress the gas pedal and there is a very hard cliff (cutoff) at 1300 RPM, the tach drops like a rock back to idle. Once back to idle, it picks back up again. Holding the gas pedal down just bounces the tach (rpm) from idle to 1300 RPM. If I rev it up very quickly and get the tach to bounce above 2500 RPM, it picks up and run fine. If I let it drop below 2500 RPM, it drops to idle and comes back up to the 1300 RPM and starts all over again.
If I am driving, I can downshift and get it above 3000 rpm, and it’s fine. When I drive it a while above 2500 rpm for about a mile, it goes back to normal, idles, revs, etc.
If it is idling, I have to “bounce” the tach quickly to get it above 2500, where it will pick up and run fine. If I drive it normally (not really my style), it never goes into the “mode” and just runs perfectly.
Setting overnight, with or without the battery disconnected, it will stay in the mode until I bounce the tach above 2500 rpm, slide the clutch, and drive about a mile.
Disconnecting the TPS temporarily takes it out of this mode, but plugging it back it, goes right back to where it was.
Strange? Hope somebody here can help. This is annoying.
01-21-2014 | 10:14 PM
#4
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Testing the TPS
For turbocharged cars:
1. Disconnect the electrical connector for the DME
control unit.
2. Connect an ohmmeter between terminal 2 on the DME
wiring harness plug and ground. This will check the idle
contact.
3. With the throttle closed, the ohmmeter should read
between 0 - 10 ohms. With the throttle open, the ohmmeter
should read infinite (∞). The switch in resistance must
occur as soon as the throttle starts to open (approximately
1°).
4. Disconnect the electrical connector for the KLR
control unit.
5. Connect an ohmmeter between terminals 22 and 23 on the
KLR wiring harness plug. With the throttle closed, the
ohmmeter should read between 320 - 670 ohms.
6. Slowly open the throttle to the wide open throttle
(WOT) position. As the throttle opens, the resistance should
continuously increase to full open resistance without any
breaks. Full open resistance is 2.7 - 4.7 Kohms.
1. Disconnect the electrical connector for the DME
control unit.
2. Connect an ohmmeter between terminal 2 on the DME
wiring harness plug and ground. This will check the idle
contact.
3. With the throttle closed, the ohmmeter should read
between 0 - 10 ohms. With the throttle open, the ohmmeter
should read infinite (∞). The switch in resistance must
occur as soon as the throttle starts to open (approximately
1°).
4. Disconnect the electrical connector for the KLR
control unit.
5. Connect an ohmmeter between terminals 22 and 23 on the
KLR wiring harness plug. With the throttle closed, the
ohmmeter should read between 320 - 670 ohms.
6. Slowly open the throttle to the wide open throttle
(WOT) position. As the throttle opens, the resistance should
continuously increase to full open resistance without any
breaks. Full open resistance is 2.7 - 4.7 Kohms.