Check Engine Light--Engine Misfires--fault code P0300
03-03-2005, 05:39 PM
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Check Engine Light--Engine Misfires--fault code P0300
I realize there is another thread with a similar discussion, but the problem I'm trying to diagnose is a little different.
On a 1997 Boxster (haven't added it to my signature yet), the check engine comes on (occasionally getting angry and flashing) and the fault codes that come up each time are P0300 (multiple engine misfires), P0304 (misfire on cylinder 4), P0305 (misfire on cylinder 5) and P0306 (misfire on cylinder 6). The check engine light only comes on once the car has gotten hot (not overheating, just normal operating temperature for a while). It also will come on even if the car is driven very easy--less than 4k rpm (so it isn't a problem that appears only above 5k rpm as others have had).
Having searched the Rennlist and Pelican Parts boards, I've tried a number of things...
1. Swapped the pre-cat O2 sensors between the left and right banks.
2. Replaced the ignition coils for cylinders 4, 5 and 6 and checked connections.
3. Replaced the fuel pressure regulator and the fuel injectors on bank 2 (cylinders 4, 5 and 6), and checked connections on the wiring harness.
4. Replaced the cam position sensor on bank 2.
5. Checked the resistance on the variocam solenoid on bank 2, and it was consistent with the resistance measured on the solenoid on bank 1 as well as the resistance measured and posted by others--and it is definitely not open loop or shorted.
6. Replaced the knock sensor on bank 2.
None of the above has had any effect. The fuel filter is brand new, so that shouldn't be the problem. The spark plugs are also brand new, and I've checked that they are the correct ones, as well as visually inspected the one in cylinder 6 and it looked good.
Car runs and feels great, with no detectable problem. I'm at a complete loss on this one as to what it could be as I've pretty much run through all of the suggestions I've been able to find. Anyone have any other suggestions as to what might be causing the fault codes?
On a 1997 Boxster (haven't added it to my signature yet), the check engine comes on (occasionally getting angry and flashing) and the fault codes that come up each time are P0300 (multiple engine misfires), P0304 (misfire on cylinder 4), P0305 (misfire on cylinder 5) and P0306 (misfire on cylinder 6). The check engine light only comes on once the car has gotten hot (not overheating, just normal operating temperature for a while). It also will come on even if the car is driven very easy--less than 4k rpm (so it isn't a problem that appears only above 5k rpm as others have had).
Having searched the Rennlist and Pelican Parts boards, I've tried a number of things...
1. Swapped the pre-cat O2 sensors between the left and right banks.
2. Replaced the ignition coils for cylinders 4, 5 and 6 and checked connections.
3. Replaced the fuel pressure regulator and the fuel injectors on bank 2 (cylinders 4, 5 and 6), and checked connections on the wiring harness.
4. Replaced the cam position sensor on bank 2.
5. Checked the resistance on the variocam solenoid on bank 2, and it was consistent with the resistance measured on the solenoid on bank 1 as well as the resistance measured and posted by others--and it is definitely not open loop or shorted.
6. Replaced the knock sensor on bank 2.
None of the above has had any effect. The fuel filter is brand new, so that shouldn't be the problem. The spark plugs are also brand new, and I've checked that they are the correct ones, as well as visually inspected the one in cylinder 6 and it looked good.
Car runs and feels great, with no detectable problem. I'm at a complete loss on this one as to what it could be as I've pretty much run through all of the suggestions I've been able to find. Anyone have any other suggestions as to what might be causing the fault codes?
03-05-2005, 02:21 PM
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From what Ive seen, when you have multiple misfires on the same bank, it is usually camshaft related...If it was o2 sensor related it would have o2 sensor related faults or fuel trim related faults...Same thing w/ vacuum leaks and leaky injectors...
I know you checked the resistance of the cam solenoid but it may change when the engine gets hot...I would suspect the vario-cam solenoid is acting up intermittently...You could swap it w/ the other side to see if its the culprit or just replace it...If you cant find out what it is,the dealership usually charges 1 hour for diagnosis. They can actually test the solenoid through drive links and tell you for sure if that is is or what may be the problem...
I would use a logic probe and apply voltage to the solenoid to see if it actuates like its supposed to...
You should here it click everytime,if not then its on its way out....Good luck!!
I know you checked the resistance of the cam solenoid but it may change when the engine gets hot...I would suspect the vario-cam solenoid is acting up intermittently...You could swap it w/ the other side to see if its the culprit or just replace it...If you cant find out what it is,the dealership usually charges 1 hour for diagnosis. They can actually test the solenoid through drive links and tell you for sure if that is is or what may be the problem...
I would use a logic probe and apply voltage to the solenoid to see if it actuates like its supposed to...
You should here it click everytime,if not then its on its way out....Good luck!!
03-06-2005, 05:16 PM
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Thanks all for the additional suggestions. A few updates:
Cabrio993: Just replaced the alternator and have checked the belt, so I'm very confident that isn't the problem.
Hammer502: Thanks for the PM. I've sprayed brake parts cleaner around the intake manifold and there doesn't appear to be any leaks there (normally if there were it would suck in the brake parts cleaner and there would be a surge in the idle.
Pyroproblem: My thinking is along what you suggested. I replaced the cam solenoid two nights ago...had a spare one from another motor. It now takes a little bit longer for the check engine light to come on, but it still comes on with exactly the same codes. Like before, it isn't until the car has been at operating temperature for a while that it comes on. Maybe the spare one was also bad, but that seems like a very low probability.
At this point I think I'm going to take it to the dealership and have them spend an hour or two trying to diagnose it with their computer, which can sometimes do a lot more and reveal a lot more information than the generic OBDII scanners.
Cabrio993: Just replaced the alternator and have checked the belt, so I'm very confident that isn't the problem.
Hammer502: Thanks for the PM. I've sprayed brake parts cleaner around the intake manifold and there doesn't appear to be any leaks there (normally if there were it would suck in the brake parts cleaner and there would be a surge in the idle.
Pyroproblem: My thinking is along what you suggested. I replaced the cam solenoid two nights ago...had a spare one from another motor. It now takes a little bit longer for the check engine light to come on, but it still comes on with exactly the same codes. Like before, it isn't until the car has been at operating temperature for a while that it comes on. Maybe the spare one was also bad, but that seems like a very low probability.
At this point I think I'm going to take it to the dealership and have them spend an hour or two trying to diagnose it with their computer, which can sometimes do a lot more and reveal a lot more information than the generic OBDII scanners.
03-21-2005, 04:29 PM
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A final update for anyone who does a search and comes across this posting. The problem turned out to be that the camshafts were out of time...were off by one tooth. In addition, the tensioner pad on the tensioner that is between the two camshafts on the bank 4-6 had worn excessively and instead of only having two small holes in it to allow oil onto the chain had much larger holes that allowed too much oil out and prevented the tensioner from providing the proper amount of tension...this is probably what allowed the chain to slip a tooth and get off in the first place. After a lot of expensive parts, the dealer fixed this all so it is back together and so far at least it hasn't been throwing those codes.
