QuestionQUESTION: Hi, My car started misfiring about 2 months back and the check light was on. It randomly misfires and the rpm goes down suddenly to zero and then shoots back while the car takes a jerk. Also while in this condition, if I apply brakes at a stop sign, my car starts misfiring and turns off.I've shown it to 2 mechanics. The 1'st one did a complete tune-up, changed the O2 sensor and the crank sensor and said it should be good. But then it started giving me the same problem. The 2nd mechanic said that it was misfiring because of a fault MAF sensor. I got that replaced and the check light didn't show up any more. It still gives me the same problem. I asked him if the knock sensor or the ignition coils were defective, he said he didn't get any code for a faulty knock sensor or defective coils. I've already shelled out more than $500. Please help.
ANSWER: Mizra,
Go to Autozone or Checker or a parts store that will read the codes for free and email them back to me. I would think the distributor is defective and needs to be replaced. But, I would like to see that random misfire code verified before I visualize it on-line.
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QUESTION: Hi,
As suggested by you I went to Autozone to get the codes, but the problem is that the device they use to monitor the check engine light was compatible only for 1996 and newer car models (mine is 1995 maxima). Also the check engine light is not on as of now. And regarding the distributor, the personnel at Autozone said my car doesn't have a distributor, rather has 6 coils, one for each cylinder. What would you suggest? Thanks.
ANSWER: Mizra,
Since yours is not OBD II you can read the codes this way.
The ECU has a window on one side to view a red LED and a green LED - when checking fault codes, a red flash is worth 10, and a green flash is worth 1. So for example, the code to say that everything is functioning normally would be 5 red flashes and 5 green flashes - the code is 55.
The ECU has 5 modes of operation, for diagnostics codes, it has to be set to mode 3.
1. Make sure the screw next to the viewing window is turned clockwise.
2. Turn the ignition on
3. Both LEDs with flash once, then a pause, then a second time, then a pause, etc. etc. up to 5 times then will repeat the process. After is has flashed 3 times then turn the screw completely anti-clockwise. - this will select mode 3.
4. The LEDs will now flash codes. 55 means that everything is normal. The rest are written below.
5. When finished, turn the screw back to clockwise and the ECU will reset itself automatically.
Don't worry about the '5th cylinder misfire' and '6th cylinder misfire' or anything, the codes are the same for all Nissans.
11 Crank Angle Sensor/Camshaft Position Sensor.
12 Air Flow Meter/Mass Air Flow Sensor.
13 Engine Coolant Temperature Sensor.
14 Vehicle Speed Sensor.
21 Ignition Signal.
22 Fuel Pump.
23 Idle Switch.
24 Throttle Valve Switch.
25 Idle Speed Control Valve.
28 Cooling Fan Circuit.
31 ECM.
32 EGR Function.
33 Heated Oxygen Sensor.
34 Knock Sensor.
35 Exhaust Gas Temperature Sensor.
36 EGR Control-Back Pressure Transducer.
37 Knock Sensor.
38 Right hand bank Closed Loop (B2).
41 Intake Air Temperature Sensor.
42 Fuel Temperature Sensor.
43 Throttle Position Sensor.
45 Injector Leak.
47 Crankshaft Position Sensor.
51 Injector Circuit.
53 Oxygen Sensor.
54 A/T Control.
55 No Malfunction.
63 No. 6 Cylinder Misfire.
64 No. 5 Cylinder Misfire.
65 No. 4 Cylinder Misfire.
66 No. 3 Cylinder Misfire.
67 No. 2 Cylinder Misfire.
68 No. 1 Cylinder Misfire.
71 Random Misfire.
72 TWC Function right hand bank.
73 TWC Function right hand bank.
76 Fuel Injection System Function right hand bank.
77 Rear Heated Oxygen Sensor Circuit.
82 Crankshaft Position Sensor.
84 A/T Diagnosis Communication Line.
85 VTC Solenoid Valve Circuit.
86 Fuel Injection System Function right hand bank.
87 Canister Control Solenoid Valve Circuit.
91 Front Heated Oxygen Sensor Heater Circuit right hand bank.
94 TCC Solenoid Valve.
95 Crankshaft Position Sensor.
98 Engine Coolant Temperature Sensor.
101 Front Heated Oxygen Sensor Heater Circuit right hand bank.
103 Park/Neutral Position Switch Circuit.
105 EGR and EGR Canister Control Solenoid Valve Circuit.
108 Canister Purge Control Valve Circuit
If you have a defective coil it should show up.
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QUESTION: I checked the codes.. It shows 55 which means everything is working normal, but I still have the problem and looks like the misfiring is increasing everyday. Also once I put my car in the parking gear, the car looks more stable and the misfiring reduces (although it still misfires sometimes while in the park gear) but its almost quite frequent while driving at low speeds under 35 mph's. I showed my car again at Midas and another mechanic, both had no clue what was going on. In fact my car was surprisingly working fine when I took it to the mechanics but again started misfiring later.
AnswerMirza,
If the plugs are not new you could move them around and see if the misfire follows the plug. The coils are the same way. But, you need to get a oscilloscope to check the firing cycle of the coils and what the plugs are doing. A Sun machine is excellent for this but most shops only have the new type scanner. You could have a defective coil that only messes up on occasion and will have to be tracked or even a cracked spark plus that is doing the same thing.
