Misfires after 15-20 minutes of operation
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Joined: Jun 2024
Posts: 12
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From: Sagamihara, Japan
Misfires after 15-20 minutes of operation
Just as the title states, I am experiencing an issue where my car starts to feel like it is re-entering orbit, all the while responding sluggishly with short bursts, and the car sounds more like a Subaru boxer engine than my beloved 4g63. I bought the car at auction in which the original owner did the following mods to the car:
- Blitz upgraded FMIC
- Blitz Turbo Timer
- Greddy Nur Spec Exhaust
- HKS Racing Suction Intake
- Project Mu Calipers
Since owning the car, I have had the following mods done to the same car, in the order from oldest to newest:
- Replaced double DINN stereo mini-disc head unit with Kenwood double DINN
- Link G4X ECU
- Ogura 659 twin clutch
- RSE 272 Cams (starting having issues with aggressive tuning at this point)
- Greddy Profec boost controller installed
- 265 Fuel Pump
- Bosch 850cc fuel injectors (two detunes from the aggressive tune given with the cams listed above, this is where the issues really starting kicking off)
- Timing belt replacement
- Upgraded alternator installed
- Starter motor replacement
- A/C condensor replaced (not believed to be related, the car was just not producing cold air anymore)
- Ignition Product R35 ignition coil pack installed
- All spark plugs replaced
I hooked up my laptop to the ECU's USB cable at a couple points when the car was acting goofy, and while it did show some interesting items, no error codes were produced. Biggest items of interest was that my lambda average was .502, but the AFR/Target lambda was set to .964; My Intake Air Temp (IAT) was also reading 63 celcius / 145 Fahrenheit. So far I have been told to have my coil pack and plugs rechecked (especially the harness), check for any cracked sensors (specifically O2, cam, and crank). I only have the knowledge base to clean the MAF myself, everything else means a trip to the shop. I welcome a trip to the shop, but the same shop who has been doing all of my work is underwater with work and was at odds with what the issue might be. Does anyone have any suggestions or experience with these sort of symptoms?
- Blitz upgraded FMIC
- Blitz Turbo Timer
- Greddy Nur Spec Exhaust
- HKS Racing Suction Intake
- Project Mu Calipers
Since owning the car, I have had the following mods done to the same car, in the order from oldest to newest:
- Replaced double DINN stereo mini-disc head unit with Kenwood double DINN
- Link G4X ECU
- Ogura 659 twin clutch
- RSE 272 Cams (starting having issues with aggressive tuning at this point)
- Greddy Profec boost controller installed
- 265 Fuel Pump
- Bosch 850cc fuel injectors (two detunes from the aggressive tune given with the cams listed above, this is where the issues really starting kicking off)
- Timing belt replacement
- Upgraded alternator installed
- Starter motor replacement
- A/C condensor replaced (not believed to be related, the car was just not producing cold air anymore)
- Ignition Product R35 ignition coil pack installed
- All spark plugs replaced
I hooked up my laptop to the ECU's USB cable at a couple points when the car was acting goofy, and while it did show some interesting items, no error codes were produced. Biggest items of interest was that my lambda average was .502, but the AFR/Target lambda was set to .964; My Intake Air Temp (IAT) was also reading 63 celcius / 145 Fahrenheit. So far I have been told to have my coil pack and plugs rechecked (especially the harness), check for any cracked sensors (specifically O2, cam, and crank). I only have the knowledge base to clean the MAF myself, everything else means a trip to the shop. I welcome a trip to the shop, but the same shop who has been doing all of my work is underwater with work and was at odds with what the issue might be. Does anyone have any suggestions or experience with these sort of symptoms?
Evolved Member
Joined: Apr 2011
Posts: 871
Likes: 301
From: WI
Have you checked the coil harness? I had a very similar issue that ended up being a bad crimp in the coil on plug harness that was causing 2 cylinders to drop sometimes. Replaced the harness and haven't had an issue since.
The IAT is also interesting, I would check that harness and sensor thoroughly as well.
The IAT is also interesting, I would check that harness and sensor thoroughly as well.
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