Extremely Stubborn FI Misfire Issue
 

Hey guys,

I have been having a big misfire issue since last August; and it's driving me crazy. I had 10k miles on my Fast Intentions kit when the issues started, and I'll list the steps I have taken to fix the issue. I have been in contact with Fast Intentions, Specialty Z, and a shop in my area to try and fix the issue, but no fruit yet.

First of all, the major issue/code has been P0302, Cylinder 2 Misfire, and the car has intermittent, very rough idles and cruises. Some times, the car will be perfect for 5-10 miles and then will have horrible misfires that bogs it down and ends up flashing the service engine soon light. It seems that the problem occurs after the engine warms up more than other times.

Other days, it will be constant, and then when the service engine light comes on, the misfires go away for an instant (like 10 seconds), and then it will come back. I also have been getting cylinder 6 misfire (P0306) and random misfire (P0300) codes.

I have done the following
-- swapped injector 2 out for a new one
--- swapped coil packs on 1 & 2 -- misfire stays on 2
-- replaced all 6 spark plugs with new ones
--performed compression test on 1 & 2 --- were normal.
-- replaced factory PCV routing with new PCV valves and breathers on the ends to vent to atmosphere, but it seemed to run worse like this, so I recently put Z1's silicone hoses on as factory replacements. When I first put these on, the car was FLAWLESS for 15 miles. Then the misses just came back. Almost like once the ECU adjusts the problem reappears.

Recently, a pending code came up: P2A03, which is upstream O2 air/fuel sensor bank 2. I'm wondering if the air fuel sensor upstream went bad... When would the car NOT rely on the O2 sensor for AFR? That would explain the misfires inexplicably going away for a few seconds/minutes.

Below is a pic of my old spark plugs, ordered 1,3,5 on the left, bottom to top, and 2,4,6 on the right, bottom to top. Plug number 4 seems to be the most blackened, but 2 is dark as well. What would cause cylinder 2 issues to transfer over to cylinder 4? The problem definitely seems to be with bank 2.


Attachment 103714


Here is some recent freeze frame data:

Freeze frame report generated by Torque for Android
================================================== =======
Vehicle Manufacturer: Nissan
Vehicle Calibration ID: 11A39A

V3EV0A

Freeze frame information:
------------------
Fuel Status = 0 byte
Engine Load = 36.078 %
Engine Coolant Temperature = 188.6 °F
Fuel Trim Bank 1 Short Term = -8.594 %
Fuel Trim Bank 1 Long Term = 6.25 %
Fuel Trim Bank 2 Short Term = 14.844 %
Fuel Trim Bank 2 Long Term = 9.375 %
Intake Manifold Pressure = 13.343 psi
Engine RPM = 2,875 rpm
Speed (OBD) = 75.807 mph
Timing Advance = 23 °
Intake Air Temperature = 86 °F
Throttle Position(Manifold) = 17.255 %
Run time since engine start = 836 s
Distance travelled with MIL/CEL lit = 0 miles
O2 Sensor1 Equivalence Ratio = 1
O2 Sensor5 Equivalence Ratio = 1
Fuel Level (From Engine ECU) = 100 %
Distance travelled since codes cleared = 17.398 miles
Evap System Vapour Pressure = 0 Pa
Barometric pressure (from vehicle) = 14.649 psi
Catalyst Temperature (Bank 1,Sensor 1) = 1,076 °F
Catalyst Temperature (Bank 2,Sensor 1) = 1,076 °F
PID: 41 = 0
Voltage (Control Module) = 13.92 V
Engine Load(Absolute) = 36.863 %
Commanded Equivalence Ratio(lambda) = 1.005
Relative Throttle Position = 12.549 %
Absolute Throttle Position B = 17.255 %
Accelerator PedalPosition D = 27.451 %
Accelerator PedalPosition E = 27.451 %


End of report.



Any ideas would be greatly appreciated.

GTR plugs? Gapped correctly?

Thats very odd.

HKS racing M40HL plugs. Part of the Fast Intentions Kit. All pre-gapped by HKS

Cylinder 2 and 6 is also bank 2 so the sensor could be going bad and causing the misfire. Based on your fuel trims bank 2 is slightly high. It shows slight lean condition. Also you could try to clean your MAF sensors to see if it helps. During cold start, the ecu will run in open loop which is predetermined value(ignores af sensors). Once the warm up cycle ends it gets the readings from its sensors and goes to closed loop. When you're cruising the car is in closed loop and if the sensor is faulty it may cause incorrect a/f mixture. Any time you accelerate or decelerate the car is in open loop therefore the misfire might not show during these conditions. You could do simple test like putting the car into limp mode by unplugging your MAF, let the code show up. Plug the sensor back in but don't clear the code. Drive the car for few miles, let the car warm up and see if the misfire occurs. If it doesn't then you'll know that your spark plugs, coils etc are in good shape.

change the o2 sensor, I had this Exact same issue.

Also smoke test it, the smallest vacuum leak can cause a misfire.

do you have factory cats in still?

Mine melted inside and pluged the cat, this caused the bank 2 sensor to **** out. Switched to test pipes, new sensor, all is well 10,000 kms later.

I have MIL spec 100 cell race cats in. I don't think they're easy to kill off, but I suppose it's a possibility.

I kept getting p0300 and p0306 almost every time I drove my car. I richened up the tune just a little under drivability and I haven't gotten a code again yet. I expect the p0300 to come again, but not the p0306. Idk if that will be your issue but it seems to have fixed mine.

Spoke too soon. Right after posting this I got both codes again...

Im running with the same issues when i installed my long tube headers. I think one of my 02 sensors is ****** or i didnt tighten it good enough. Very frustrating when my inspection sticker expired and have to fix this ****.

im having misfires with my FI kit as well.The misfire with me occurs at heavy acceleration. Gas gets cut off as well. Recently my car died on the freeway lol. Sebastian is thinking fuel pump related. Car is in the shop at the moment, trying to get everything solved. Ill keep you updated.

Please do. I ordered a new upstream a/f sensor, but I'm not so sure that's the issue. I did a bunch of data logging, and it looks like the o2 sensor voltages are alive, so I doubt they are dead. One thing that is interesting is my Camshaft Adv Sensor in Bank 2 is stuck at -128. I'm looking into it further as I type this.

got my car back, the fuel pump was the culprit. Seb said the hoses got eaten up by the ethanol. Rob at Z car garage, put in a new fuel pump/replaced the hoses, and everything is back to normal.

This is way overdue, but I found the issue. It was a faulty injector *sub*harness. Runs like a dream now.

Always the little stuff. Props to R/T Tuning.