Cel
04-08-2004, 04:02 PM
#1
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Location: Indianapolis
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Cel
Hi All,
Since I have purchased my '97 cab some weeks ago, I have had a recurring problem with the CEL. Maybe someone here can shed a little light on things.
The car runs great and the motor is strong, but about every 100 miles or so, on comes the light. I have an OBD11 scan tool and it tells me the same thing each time. 3 codes, misfire on cylinder 3, misfire on cylinder 6 and multiple misfires. There are no discernible real life issues with the car when this happens, no burps, hiccups or anything.
Now, I knew when I bought the car that this could be an issue, but after much deliberation, etc. etc, I went for it anyway, because the deal was right. In the past couple of months, these are the items that were changed by the previous owner in an attempt to fix the problem.
1. New set of injectors
2. New Plugs
3. New filters throughout
4. New plug leads
5. New distributor caps
6. New injector wiring harness
As mentioned, everything seems to be working okay other than the light coming on. I understand from a few searches, that the CEL is particularly sensitive on these cars, or at least some of the sensors that activate it are.
However, I wonder if anyone knows which sensors are used to determine that a misfire has occured.??
The research and parts changes done on the car were performed by a very reputable Independent in this area and it was only after talking to him that I bought the car, as he felt that the car was solid and a good buy.
I am not complaining after the fact, but there has to be a way to cure the problem or at least understand it.
All input gratefully accepted.
Since I have purchased my '97 cab some weeks ago, I have had a recurring problem with the CEL. Maybe someone here can shed a little light on things.
The car runs great and the motor is strong, but about every 100 miles or so, on comes the light. I have an OBD11 scan tool and it tells me the same thing each time. 3 codes, misfire on cylinder 3, misfire on cylinder 6 and multiple misfires. There are no discernible real life issues with the car when this happens, no burps, hiccups or anything.
Now, I knew when I bought the car that this could be an issue, but after much deliberation, etc. etc, I went for it anyway, because the deal was right. In the past couple of months, these are the items that were changed by the previous owner in an attempt to fix the problem.
1. New set of injectors
2. New Plugs
3. New filters throughout
4. New plug leads
5. New distributor caps
6. New injector wiring harness
As mentioned, everything seems to be working okay other than the light coming on. I understand from a few searches, that the CEL is particularly sensitive on these cars, or at least some of the sensors that activate it are.
However, I wonder if anyone knows which sensors are used to determine that a misfire has occured.??
The research and parts changes done on the car were performed by a very reputable Independent in this area and it was only after talking to him that I bought the car, as he felt that the car was solid and a good buy.
I am not complaining after the fact, but there has to be a way to cure the problem or at least understand it.
All input gratefully accepted.
04-08-2004, 04:34 PM
#2
A misfire is determined by checking changes to the engine's RPM, i.e the DME
calculates the "on the fly" average RPM and checks for drops in RPMs. These
are common occurences on 993s/996s with OBDII tests.
Possible causes:
1. O2 sensors
2. MAFS problems (e.g. K&N filters)
3. intake air leaks
4. high voltage breakdown in the distributor
5. weak/bad igntion coils
calculates the "on the fly" average RPM and checks for drops in RPMs. These
are common occurences on 993s/996s with OBDII tests.
Possible causes:
1. O2 sensors
2. MAFS problems (e.g. K&N filters)
3. intake air leaks
4. high voltage breakdown in the distributor
5. weak/bad igntion coils
04-08-2004, 04:47 PM
#3
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Join Date: Jun 2001
Location: SF Bay Area (Lafayette)
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I had the same issue with my '96 about a year or two ago. Random misfires. I switched gas stations (my mechanic said the local Chevron station used bad gas) and cut out short trips. Since then (knock on wood) no more misfire readings. Since your car was also giving CELs to the prior owner, it doesn't sound like it could be crappy gas, but I just thought you'd appreciate another guy's story. Good luck.