Misfire in 996 Turbo
12-13-2012, 03:25 PM
#16
Racer
12-14-2012, 12:37 PM
#17
Race Director
Sorry to bump an old thread, but I have a similar sparatic issue on mine. Every so often, under acceleration only, it will stumble or shudder. Not really bad but enough to bother me.
The car has been sitting for years, its an 02 with 9800 miles. Im assuming the plugs might be fouled or corroded.
Its kinda feels like it may be a boost leak. Funny thing about it, I paid for a PPI at a Porsche dealership that said the car was PERFECT.
The car has been sitting for years, its an 02 with 9800 miles. Im assuming the plugs might be fouled or corroded.
Its kinda feels like it may be a boost leak. Funny thing about it, I paid for a PPI at a Porsche dealership that said the car was PERFECT.
My experience with a new Infiniti that sat around for about 6 months, driven a few times, but not ever filled with gasoline, was that the engine was flat.
No misfires or other untoward behavior but the engine felt weak. Since I was unfamiliar with the car -- it is my sister's and I never drove it before -- I thought this was normal. She had raved about the engine's performance and while I can't recall the hp/torque numbers now I do recall they seemed to suggest the engine should be a good performer.
I drove the vehicle enough to require refilling the tank. After the refueling, the change in the engine's performance was markedly improved. The transition was almost like night and day.
In the case of your car I'd consider using a bottle or two of Techron as per directions though I'd use this after getting some fresh gas in the tank.
Be sure to change the oil/filter after the last tank with Techron in it is down to 1/4 level.
12-14-2012, 12:52 PM
#18
Track Day
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Misfire Solution Found
I am anxious to hear the collective ideas from all of you regarding my 2003TT X-50. The car currently has 40K miles (approx 65K Km) on the odometer and the following engine modifications completed at around 15K miles (24+Km):
• Billet diverter valves
• B&B 100 cell cat exhaust
• GIAC Software
• EVOMS Air intake
At 32K miles the car began to have a slight “miss” most noticeable from first to second gear at 1800 RPM and occasionally at 4800 RPM at 1 Bar. At 34K miles, the MAF sensor went out while at the track. I was hopeful that replacing this would cure the slow speed miss and occasional high-speed one that was now very evident between 4200-4800 RPM; this was not the case. I had the dealer do a smoke test to determine if there was a vacuum leak and there was none. My extended warranty was about to end so I had a complete inspection of the car including leak-down and the engine passed with excellence. New plugs were placed at that time. I am still experiencing the above misses that feel somewhat like a Rev limiter nibbling away at the fuel or spark. Today I replaced the fuel filter with certainty that the problem would be solved: no such luck. To be sure, it is not the GIAC tune; I re-mapped the software back to stock with no fix. The car is very strong and in second gear under boost, will fly past the hic up with just a small fart, but in third and fourth gears, where more time is spent, it becomes quite noticeable. A local Porsche mechanic is suggesting I replace the coil packs, as this has been a problem for the 996 turbos'. When I checked with the dealer, there is a coil pack ID number of 997 602 104 00 which seems to indicate a newer version. I have no “check engine lights” nor is this car driven in the winter elements. My son thinks a diverter valve may be stuck.
Summarizing what I have done to find a cure:
• Replaced plugs
• Replaced MAF sensor
• Replaced fuel filter
• Ruled out vacuum leaks as a source
• Switched software back to stock
Who agrees with the mechanic and who with my son? Are there any other possibilities that I have not considered? Thank you!
• Billet diverter valves
• B&B 100 cell cat exhaust
• GIAC Software
• EVOMS Air intake
At 32K miles the car began to have a slight “miss” most noticeable from first to second gear at 1800 RPM and occasionally at 4800 RPM at 1 Bar. At 34K miles, the MAF sensor went out while at the track. I was hopeful that replacing this would cure the slow speed miss and occasional high-speed one that was now very evident between 4200-4800 RPM; this was not the case. I had the dealer do a smoke test to determine if there was a vacuum leak and there was none. My extended warranty was about to end so I had a complete inspection of the car including leak-down and the engine passed with excellence. New plugs were placed at that time. I am still experiencing the above misses that feel somewhat like a Rev limiter nibbling away at the fuel or spark. Today I replaced the fuel filter with certainty that the problem would be solved: no such luck. To be sure, it is not the GIAC tune; I re-mapped the software back to stock with no fix. The car is very strong and in second gear under boost, will fly past the hic up with just a small fart, but in third and fourth gears, where more time is spent, it becomes quite noticeable. A local Porsche mechanic is suggesting I replace the coil packs, as this has been a problem for the 996 turbos'. When I checked with the dealer, there is a coil pack ID number of 997 602 104 00 which seems to indicate a newer version. I have no “check engine lights” nor is this car driven in the winter elements. My son thinks a diverter valve may be stuck.
Summarizing what I have done to find a cure:
• Replaced plugs
• Replaced MAF sensor
• Replaced fuel filter
• Ruled out vacuum leaks as a source
• Switched software back to stock
Who agrees with the mechanic and who with my son? Are there any other possibilities that I have not considered? Thank you!
12-14-2012, 03:56 PM
#19
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Macster, NSX car could have left the factory with the Beru FR5 plugs. My recommendation is to pick up a good code reader and check for any pending misfire codes.
Mike, it's good that you were able to finally "cure" your misfires. It's looks like the loose spark plugs were the culprit. Please note that Per Porsche Service Manual the recommended spark plug gap is 1.6mm (this has been debated for many years as a error) The 1.0mm gap on stock Beru or Bosch is considered acceptable.
The shops that you have taken the car to for repair, might have missed the fact that you must torque the spark plugs twice to ensure that they don't loosen up.
Mike, it's good that you were able to finally "cure" your misfires. It's looks like the loose spark plugs were the culprit. Please note that Per Porsche Service Manual the recommended spark plug gap is 1.6mm (this has been debated for many years as a error) The 1.0mm gap on stock Beru or Bosch is considered acceptable.
The shops that you have taken the car to for repair, might have missed the fact that you must torque the spark plugs twice to ensure that they don't loosen up.
