Inherent Fire Problems?
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From: Bird lover in Sharpsburg
That is a Porsche added system, along with it cost and complexity to save folks from them self.
My 87 does not have it, but when I do the harness for the engine compartment I may very well add it as I have all the rest of the parts to install a digital dash in my 87.
I still am not sure it is a good thing or not, I guess it is, but if you can not tell your car has dropped a cylinder, much less 4, maybe knitting is better suited for that person.
I agree that if there is a problem, you need to stop and get the towing service to come get your car, do not drive it.
My 87 does not have it, but when I do the harness for the engine compartment I may very well add it as I have all the rest of the parts to install a digital dash in my 87.
I still am not sure it is a good thing or not, I guess it is, but if you can not tell your car has dropped a cylinder, much less 4, maybe knitting is better suited for that person.
I agree that if there is a problem, you need to stop and get the towing service to come get your car, do not drive it.
One fire danger that is inherent in the 32-valve models concerns the ignition systems - that is systems with an "s".
On your '85 you have two independent ignition systems. If one fails, the car still runs - and that is not really a good thing.
You also have catalytic converters. If you drive the car with half the cylinders not firing, you are pumping quite a bit of unburned fuel directly into the cats. The cats will burn the fuel, get red hot, and set the car on fire.
If your car loses a lot of power, STOP! Do not pass Go, do not collect $100, and do NOT try to make it home, or to the shop, or anywhere else. If you drive it with a large loss of power, the chances are very good that you will burn it to the ground.
Starting in '89, Porsche added a safety system that monitored the exhaust temps on one cylinder in each set. If one sensor saw low EGT, it tripped a relay that cut off the fuel injectors on those four cylinders (two on each side of the engine).
While this system should prevent the cat fire, it is still a bit risky to drive the car with a high loss of power. If the Ignition Monitoring System has been disabled, you will burn the car. If the system works and you have no fire, you are running a high risk of breaking the driveshaft.
On your '85 you have two independent ignition systems. If one fails, the car still runs - and that is not really a good thing.
You also have catalytic converters. If you drive the car with half the cylinders not firing, you are pumping quite a bit of unburned fuel directly into the cats. The cats will burn the fuel, get red hot, and set the car on fire.
If your car loses a lot of power, STOP! Do not pass Go, do not collect $100, and do NOT try to make it home, or to the shop, or anywhere else. If you drive it with a large loss of power, the chances are very good that you will burn it to the ground.
Starting in '89, Porsche added a safety system that monitored the exhaust temps on one cylinder in each set. If one sensor saw low EGT, it tripped a relay that cut off the fuel injectors on those four cylinders (two on each side of the engine).
While this system should prevent the cat fire, it is still a bit risky to drive the car with a high loss of power. If the Ignition Monitoring System has been disabled, you will burn the car. If the system works and you have no fire, you are running a high risk of breaking the driveshaft.
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The first time my ignition monitoring system tripped and killed the injectors to 4 of the cylinders, I drove for about 5 miles before I realized what it was and stopped the car. I feel a bit stupid saying this because if I am paying attention I can tell when these cars are only running on 7 cylinders. It's harder to tell when you are cruising on variable terrian and think the car just needs more throttle because of an uphill section. Otherwise I can't expalin how I dismissed the drop off in power. And I had the carpet out of the car, so all I had to do was look over and see the relay's LED lit up, which I finally did and pulled over. On restart the condition did not return, so I drove home safely on all 8. A month later when the system tripped again, I knew immediately what it was even without the LED exposed. One other very experienced 928 owner who hangs out here had an ignition coil short out on an 86 he just bought while driving along and that started a cat fire before he stopped. In that case, unfamiliarity with a car that had mutliple other problems that might cause poor performance prevented him from making the correct diagnosis quickly enough while on the road.
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From: Bird lover in Sharpsburg
Bill, if you drove on 4 cylinders and did not know it, it must be easy to do.
So you think it is a good thing for it to be installed?
Or not have cats?
So you think it is a good thing for it to be installed?
Or not have cats?
The first time my ignition monitoring system tripped and killed the injectors to 4 of the cylinders, I drove for about 5 miles before I realized what it was and stopped the car. I feel a bit stupid saying this because if I am paying attention I can tell when these cars are only running on 7 cylinders. It's harder to tell when you are cruising on variable terrian and think the car just needs more throttle because of an uphill section. Otherwise I can't expalin how I dismissed the drop off in power. And I had the carpet out of the car, so all I had to do was look over and see the relay's LED lit up, which I finally did and pulled over. On restart the condition did not return, so I drove home safely on all 8. A month later when the system tripped again, I knew immediately what it was even without the LED exposed. One other very experienced 928 owner who hangs out here had an ignition coil short out on an 86 while driving along and that started a cat fire before he stopped.
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From: Johnson City, TN
One fire danger that is inherent in the 32-valve models concerns the ignition systems - that is systems with an "s".
On your '85 you have two independent ignition systems. If one fails, the car still runs - and that is not really a good thing.
You also have catalytic converters. If you drive the car with half the cylinders not firing, you are pumping quite a bit of unburned fuel directly into the cats. The cats will burn the fuel, get red hot, and set the car on fire.
If your car loses a lot of power, STOP! Do not pass Go, do not collect $100, and do NOT try to make it home, or to the shop, or anywhere else. If you drive it with a large loss of power, the chances are very good that you will burn it to the ground.
Starting in '89, Porsche added a safety system that monitored the exhaust temps on one cylinder in each set. If one sensor saw low EGT, it tripped a relay that cut off the fuel injectors on those four cylinders (two on each side of the engine).
While this system should prevent the cat fire, it is still a bit risky to drive the car with a high loss of power. If the Ignition Monitoring System has been disabled, you will burn the car. If the system works and you have no fire, you are running a high risk of breaking the driveshaft.
On your '85 you have two independent ignition systems. If one fails, the car still runs - and that is not really a good thing.
You also have catalytic converters. If you drive the car with half the cylinders not firing, you are pumping quite a bit of unburned fuel directly into the cats. The cats will burn the fuel, get red hot, and set the car on fire.
If your car loses a lot of power, STOP! Do not pass Go, do not collect $100, and do NOT try to make it home, or to the shop, or anywhere else. If you drive it with a large loss of power, the chances are very good that you will burn it to the ground.
Starting in '89, Porsche added a safety system that monitored the exhaust temps on one cylinder in each set. If one sensor saw low EGT, it tripped a relay that cut off the fuel injectors on those four cylinders (two on each side of the engine).
While this system should prevent the cat fire, it is still a bit risky to drive the car with a high loss of power. If the Ignition Monitoring System has been disabled, you will burn the car. If the system works and you have no fire, you are running a high risk of breaking the driveshaft.
Maybe John S. or Allan could design us an aftermarket safety cicuit or warning alarm for loss of a bank.
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From: Ball Ground, GA
On twin-ignition cars up to '88, if you feel a power loss, immediately get to a safe point out of the traffic lane. Shut down the engine, pop the hood and check both coil wires, especially the driver's side (LHD). Reroute the wires away from any metal or wire harnesses. Unplug/replug the ends. Check for moisture or dirt.
Try the car again - if it still has power loss, continued driving can be very hazardous. If it feels normal - that is, peppy - then drive on and repeat the coil wire checks at home.
Try the car again - if it still has power loss, continued driving can be very hazardous. If it feels normal - that is, peppy - then drive on and repeat the coil wire checks at home.
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So another possibility might be to install a wideband O2 sensor and have it somewhere in plain sight. If it starts to run a little sluggish, check for a really rich condition for confirmation. What do you think?
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From: Buckeye, AZ
Yeah, I can't believe I did it. Wally's caution to just pull over and examine the coils whenever you sense a loss of power is very good advice, of course. I just didn't have that at the forefront of my mind and I did not quite identify the loss of power as I had started to head up a grade (Donner Pass near Lake Tahoe). The AT downshifted and the car kept its speed and I thought, gee, that's odd that it downshifted when it did. It took me way too long to put 2 & 2 together. Of course, once it happened a second time, I knew exactly what it was in seconds. In my case, the system false alarmed, possibly due to a bad sensor, as the problem was gone on restart. After another incident, I disabled the system, confident (perhaps wrongly) that I would know if a coil dropped out. It's been 4 years or so since I did that. I am running a wideband O2 sensor. That might clue me in me if I sensed the power drop. I would rather have the system working, but I have't taken the time to diagnose the problem. Most likely it is a bad sensor. I may just need to remove and clean/reposition them.
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From: Bird lover in Sharpsburg
What I was trying to say is, that if it can happen to you, it can happen to anybody.
Yeah, I can't believe I did it. Wally's caution to just pull over and examine the coils whenever you sense a loss of power is very good advice, of course. I just didn't have that at the forefront of my mind and I did not quite identify the loss of power as I had started to head up a grade (Donner Pass near Lake Tahoe). The AT downshifted and kept its speed and I thought, gee, that's odd that it downshifted when it did. It took me way too long to put 2 & 2 together. Of course, once it happened a second time, I knew eactly what it was in seconds. In my case, the system false alarmed, possibly due to a bad sensor, as the problem was gone on restart. After another incident, I disabled the system, confident (perhaps wrongly) that I would know if a coil dropped out. It's been 4 years or so since I did that. I am running a wideband O2 sensor. That might clue me in me if I sensed the power drop. I would rather have the system working, but I have't taken the time to diagnose the problem. Most likely it is a bad sensor. I may just need to remove and clean/reposition them.
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Track Day
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From: Belgium, WI
This thread turned out to be even more informative than I expected.
Thank you all.
P.S- I found it funny that all of the "Volvo Fire" clips were all of newer Ford raped models! So yes, I do feel better. Maybe nobody thinks it is worth filming if their older models go up.
Thank you all.
P.S- I found it funny that all of the "Volvo Fire" clips were all of newer Ford raped models! So yes, I do feel better. Maybe nobody thinks it is worth filming if their older models go up.
Instructor
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From: San Francisco Bay Area, Santa Clara
Oh yea, forgot to mention the AC lines. The cause of more than one fire. More of a chance of it just leaking out slow. When you go in and replace the seals, inspect the hoses close also. Had a car a few weeks back that the pressure hose was too close to the air pump belt and it wore through it, releasing pressure at a quick rate. Had that happened at a stop, it might have been bad. As it happened at speed, I think he got a bit lucky.
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From: Abbotsford B.C.
However Mike, it would be very lean, lots of oxygen in unburnt mixtures which is what an oxygen sensor reads.....
