Yet another 996 Cylinder 1 misfire thread
11-28-2016, 01:46 AM
#301
Rennlist Member
Bravo !! I applaud your determination in getting to the resolution of this issue ! Even though it took 8 months, the main thing is it solved the problem.
01-26-2017, 04:09 PM
#302
Track Day
OK Rennlisters--
I have a 2003 996.2. I've been fighting a cylinder 1 misfire for two months now have yet to resolve it.
I think I've read everything posted on Rennlist and 6speed. I hope you can come up with something new.
Relevant Car History
Jan. 2015, 86 kmi: Replaced fuel pump. On the 996.2 the fuel filter is part of the fuel pump, which resides inside of the gas tank.
May 2015, 87 kmi: Replaced stock engine with professionally rebuilt X51 engine (see https://rennlist.com/forums/996-foru...mentation.html). Includes new IMS roller bearing, piston rings, main bearings, rod bearings, head gasket, seals, cylinder head bolts, water pump, LNE low-temperature thermostat, spark plugs. The ignition coils look new. The air intake manifold and exhaust manifold were upgraded to the X51 versions using used components. The mufflers were replaced with used Porsche Sport Exhaust (PSE) mufflers with the valves permanently wired into the "loud" position.
July 2015, 89 kmi: I was unable to get a standard Porsche X51 ECU flash, so I got one for the 996.2 X51 from Evolution Motorsports. I've noticed some hydrogen sulfide smell when I floor it and rev it up to 7000 rpm. I suspect that the flash results in a little too much fuel input at high revs, possible damaging the catalytic converters.
June-Dec. 2015: Several oil changes at 4000 miles with Joe Gibbs DT40 5W40 oil. Spin-on filter using the LNE adapter.
Nov. 2015, 95 kmi: Replaced stock springs, shocks, and sway bars with the ROW M030 version. These transmit the shock from large bumps to the chassis very well, so something like the cat cartridge or wiring could have been bumped loose.
Dec. 2015, 97 kmi: Replaced the M030 shocks with Koni FSD shocks. These take the big bumps much more smoothly.
Dec. 2015, 96.3 kmi: The problems starts. After the car had been driven about 10 minutes and was warmed up, while idling at a stoplight, the engine started running rough and the check-engine light came on. My code reader said P0300 (random cylinder misfires damaging to catalytic converter), P0301 (cylinder 1 misfire), and P0305 (cylinder 5 misfire). After a minute, it ran fine. I cleared the codes, drove some more that day, and only the cylinder 1 misfire returned. Cylinder 1 is the left side of the car toward the rear of the car. I replaced the cylinder 1 spark plug. It looked normal. At the same time I replaced the ignition coil, which looked normal and had a low resistance (I forgot what I read). The engine ran fine for 500 miles. I fixed it! Or did I?
Dec. 2015, 96.8 kmi: Regularly scheduled oil and filter change with DT40.
Dec. 2015, 96.9 kmi: Brief cylinder 1 misfire. Unplugged the connector to the ignition coil. It looks pristine inside. It was solidly clicked into place before and after inspection. I did notice that the overflow from the coolant tank has a hose that dumps right onto the coil. I moved it, but it wants to move back by itself.
Jan. 2016, 97.4 kmi: After many more cylinder 1 misfires, I replaced the cylinder 1 fuel injector with a new one. Afterward, the car ran fine for a few minutes, then the problem returned.
With my Durametric, I can turn off each fuel injector. Doing so makes it run really rough and almost die. The misfires that I have been feeling have not been that rough. I learned from the indy German car mechanic who installed my X51 engine that if the misfire is too bad, the ECU shuts off all fuel to that cylinder. Just turning the car off and back on restores the fuel flow.
Jan. 2016, 97.7 kmi: After revving it up, one time I got code P0430: catalytic converter efficiency bank 2 (which is cylinders 4-6 on the right side of the car).
Jan.-Feb. 2016 I have been looking for patterns with the misfires. The most common time is about two minutes after starting a cold engine, when idling at a stoplight. But is also occurs sometimes when the engine has been running for over 10 or even 30 minutes. It usually goes away within two minutes. I don't see a correlation with rainy days. I've gone through 4+ tanks of gas.
Porsche diagnosis protocol. For code P0301, Porsche says to do the following:
* Check fouled, faulty or incorrect spark plugs. Done (replaced).
* Check contact resistance. Looks OK at the connector to the coil. The next step would be to look for damage to the wire from the ECU (behind the back seats) and the coil.
* Check for loose contacts. See above. I looked that huge bundles of wires that connect to the ECU and didn't see anything amiss. The region was dry.
* Check for mixture too rich or lean. The MAF sensor could be a problem, but I doubt it because only one cylinder is misfiring.
* Fuel tank empty. It's not.
* Valve lifter chattering. I do hear a tick-tick-tick at same rate as the camshafts are spinning when the engine is idling. My indy says it's not a problem. It is not correlated to rough running.
* Camshaft control badly adjusted. All of cylinders in one bank would be misfiring, so that's not it.
* VarioCam does not switch over completely. Again, this should affect all cylinders in one bank.
* Check fuel pressure. I don't have the tool for that. All of the other cylinders are getting fuel, so this is probably not it.
* Check volume supply of fuel pump. See above. If I open up the port, I need a special replacement crush seal that I don't see at Pelican Parts or anywhere else.
* Check triggering of fuel injectors. To access the fuel injectors, I have to drop the engine down two inches and unplug one. I don't see how to run the engine and have the injector unplugged at the same time.
Your thoughts are appreciated!
I have a 2003 996.2. I've been fighting a cylinder 1 misfire for two months now have yet to resolve it.
I think I've read everything posted on Rennlist and 6speed. I hope you can come up with something new.Relevant Car History
Jan. 2015, 86 kmi: Replaced fuel pump. On the 996.2 the fuel filter is part of the fuel pump, which resides inside of the gas tank.
May 2015, 87 kmi: Replaced stock engine with professionally rebuilt X51 engine (see https://rennlist.com/forums/996-foru...mentation.html). Includes new IMS roller bearing, piston rings, main bearings, rod bearings, head gasket, seals, cylinder head bolts, water pump, LNE low-temperature thermostat, spark plugs. The ignition coils look new. The air intake manifold and exhaust manifold were upgraded to the X51 versions using used components. The mufflers were replaced with used Porsche Sport Exhaust (PSE) mufflers with the valves permanently wired into the "loud" position.
July 2015, 89 kmi: I was unable to get a standard Porsche X51 ECU flash, so I got one for the 996.2 X51 from Evolution Motorsports. I've noticed some hydrogen sulfide smell when I floor it and rev it up to 7000 rpm. I suspect that the flash results in a little too much fuel input at high revs, possible damaging the catalytic converters.
June-Dec. 2015: Several oil changes at 4000 miles with Joe Gibbs DT40 5W40 oil. Spin-on filter using the LNE adapter.
Nov. 2015, 95 kmi: Replaced stock springs, shocks, and sway bars with the ROW M030 version. These transmit the shock from large bumps to the chassis very well, so something like the cat cartridge or wiring could have been bumped loose.
Dec. 2015, 97 kmi: Replaced the M030 shocks with Koni FSD shocks. These take the big bumps much more smoothly.
Dec. 2015, 96.3 kmi: The problems starts. After the car had been driven about 10 minutes and was warmed up, while idling at a stoplight, the engine started running rough and the check-engine light came on. My code reader said P0300 (random cylinder misfires damaging to catalytic converter), P0301 (cylinder 1 misfire), and P0305 (cylinder 5 misfire). After a minute, it ran fine. I cleared the codes, drove some more that day, and only the cylinder 1 misfire returned. Cylinder 1 is the left side of the car toward the rear of the car. I replaced the cylinder 1 spark plug. It looked normal. At the same time I replaced the ignition coil, which looked normal and had a low resistance (I forgot what I read). The engine ran fine for 500 miles. I fixed it! Or did I?
Dec. 2015, 96.8 kmi: Regularly scheduled oil and filter change with DT40.
Dec. 2015, 96.9 kmi: Brief cylinder 1 misfire. Unplugged the connector to the ignition coil. It looks pristine inside. It was solidly clicked into place before and after inspection. I did notice that the overflow from the coolant tank has a hose that dumps right onto the coil. I moved it, but it wants to move back by itself.
Jan. 2016, 97.4 kmi: After many more cylinder 1 misfires, I replaced the cylinder 1 fuel injector with a new one. Afterward, the car ran fine for a few minutes, then the problem returned.
With my Durametric, I can turn off each fuel injector. Doing so makes it run really rough and almost die. The misfires that I have been feeling have not been that rough. I learned from the indy German car mechanic who installed my X51 engine that if the misfire is too bad, the ECU shuts off all fuel to that cylinder. Just turning the car off and back on restores the fuel flow.
Jan. 2016, 97.7 kmi: After revving it up, one time I got code P0430: catalytic converter efficiency bank 2 (which is cylinders 4-6 on the right side of the car).
Jan.-Feb. 2016 I have been looking for patterns with the misfires. The most common time is about two minutes after starting a cold engine, when idling at a stoplight. But is also occurs sometimes when the engine has been running for over 10 or even 30 minutes. It usually goes away within two minutes. I don't see a correlation with rainy days. I've gone through 4+ tanks of gas.
Porsche diagnosis protocol. For code P0301, Porsche says to do the following:
* Check fouled, faulty or incorrect spark plugs. Done (replaced).
* Check contact resistance. Looks OK at the connector to the coil. The next step would be to look for damage to the wire from the ECU (behind the back seats) and the coil.
* Check for loose contacts. See above. I looked that huge bundles of wires that connect to the ECU and didn't see anything amiss. The region was dry.
* Check for mixture too rich or lean. The MAF sensor could be a problem, but I doubt it because only one cylinder is misfiring.
* Fuel tank empty. It's not.
* Valve lifter chattering. I do hear a tick-tick-tick at same rate as the camshafts are spinning when the engine is idling. My indy says it's not a problem. It is not correlated to rough running.
* Camshaft control badly adjusted. All of cylinders in one bank would be misfiring, so that's not it.
* VarioCam does not switch over completely. Again, this should affect all cylinders in one bank.
* Check fuel pressure. I don't have the tool for that. All of the other cylinders are getting fuel, so this is probably not it.
* Check volume supply of fuel pump. See above. If I open up the port, I need a special replacement crush seal that I don't see at Pelican Parts or anywhere else.
* Check triggering of fuel injectors. To access the fuel injectors, I have to drop the engine down two inches and unplug one. I don't see how to run the engine and have the injector unplugged at the same time.
Your thoughts are appreciated!
Going through this issue with my 03 C4S on Cyl #5. Every morning, after the initial warm-up cycle, it throws a CEL P0305 if I just let it idle until warm. Sometimes I can avoid the issue by reving it to 2000 for 1-2 minutes until it warms up. Once up to temperature (160-180) the car operates normally all day. I'm leaning towards the Intake lifters getting stuck in the high-lift position. I can sometimes hear intermittent little pops from the intake. A leakdown and compression tests shows everything is Ok. Due to the cost of the intake lifters, and because I'm doing the work myself, I will try to get those lifters out, disassemble and inspect them. Based on their condition, I may try to 'fix them' and probably take them to my brothers machine shop to get the parts checked out and or micropolished. I find it ridiculous for them to be close to $200 each while the exhaust are only $23. If the problem persist, then I have no choice but to replace only the two that are suspected. Call me cheapskate if you like but that's my story.
01-26-2017, 08:17 PM
#304
Instructor
Thread Starter
Going through this issue with my 03 C4S on Cyl #5. Every morning, after the initial warm-up cycle, it throws a CEL P0305 if I just let it idle until warm. Sometimes I can avoid the issue by reving it to 2000 for 1-2 minutes until it warms up. Once up to temperature (160-180) the car operates normally all day. I'm leaning towards the Intake lifters getting stuck in the high-lift position. I can sometimes hear intermittent little pops from the intake. A leakdown and compression tests shows everything is Ok. Due to the cost of the intake lifters, and because I'm doing the work myself, I will try to get those lifters out, disassemble and inspect them. Based on their condition, I may try to 'fix them' and probably take them to my brothers machine shop to get the parts checked out and or micropolished. I find it ridiculous for them to be close to $200 each while the exhaust are only $23. If the problem persist, then I have no choice but to replace only the two that are suspected. Call me cheapskate if you like but that's my story.
The way I could tell that my car's cylinder 1 was not consistently getting the right amount of burned air-fuel mixture was starting a cold engine, letting it run for just 10 seconds, turning it off, then immediately measuring the temperature of the three bank 1 exhaust pipes with a thermocouple. Your hand might also work. My cylinder 1 was sometimes noticeably colder than the other two cylinders. You'd of course check cylinders 4, 5, and 6 on bank 2. The intermittent nature suggested one of the two cylinder 1 intake valves stuck part of the time, and that's indeed what was seen when the valve lifters were removed. You should also be able to hear a tick-tick-tick on the right side of your engine when it's running roughly. It should disappear when it's smooth.
Given the time that it will take you to pull the engine, then remove the valve cover and camshafts to get to the valve lifters, at the very least I'd put in a new intake valve lifter (see earlier in this thread for the correct latest valve lifter part number, which is not what I had after my rebuild!).
