kyleegbert

I've tried to search and follow all the advise in as many posts as seemed even minimally relevant, but I haven't been able to figure out this issue.

About 6 months ago, I started experiencing an intermittent idle problem. The issue was so minor, it wasn't worth the time to try and diagnose, and didn't really affect the car's ability or reliability. I just noticed that the car would misfire once in a while when the throttle was in between adding and removing speed while on the highway. It seemed like it was more likely to happen when it was humid/raining or perhaps at higher altitude. When I would start the car, the idle would bounce a little, running between around 650 and 850.

The issue progressed enough and after switching to an android head unit which allowed me to read my OBD II information whenever, that I started looking into it deeper and tried to slowly progress through the most likely/least expensive/least effort remedies. Here's what I've been able to discover/replace over time:
(My car is basically stock, or started that way for this description of events, following regular service intervals, driven aggressive but not extreme, first owner/bought new from dealer - 2010 Evo X GSR with 78k miles on it now)
- The misfire primarily occurs in cylinder 4, occurring more frequently at idle, at about 1-2 a minute. For my last 10 drives, I average about 45 misfires per drive. All other cylinders average close to 0. While on the highway, in a flat environment and using cruise control, it never misfires.
- I removed, inspected, and cleaned my throttle. Then reset the ECU. Originally it idled high but it learned over time.
- I checked for vacuum leaks, including the common fuel pressure regulator line which I zip tied secured.
- I ran intake cleaner through, then fuel cleaner, ultimately no effect.
- I cleaned, then replaced, my MAF sensor - no change
- I replaced my up and downstream O2 sensors, somewhat as preventative maintenance, which slightly helped in other areas, but didn't affect the problem.
- I changed out my stock intake for a K&M cone with the cold air shield. It sounds awesome, but didn't affect the problem.
- I inspected, then replaced my spark plugs, using the stock NGK ones. No effect.
- I tested each cylinder's compression which had near perfect results.
- I replaced my ignition coils with no effect.
- I resistance tested the fuel injectors, without any discoveries.
- I disconnected vacuum from the master cylinder, to rule out a leak/problem with it, which proved there was no leak there.
- I tested for a head gasket leak, which didn't result in anything.
- I thought about replacing the valve cover gasket, but decided it could wait until I have to dig deeper into the engine for a good reason.
- I ran pressurized air into my exhaust and couldn't discover any exhaust leaks

What I think I could try next, but haven't yet:
- Replacing the cam/crankshaft position sensor(s)
- Replacing the fuel injector if switching cylinder 4's with another's causing the misfires to move. I didn't want to mess with the fuel rail unless I had to.
- Replacing the boost pressure sensor
- Replacing spark plug wires

Has anyone else experienced this same or a similar issue and have any advise? Any information helps and is appreciated.

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Mode $06 report generated by Torque for Android
================================================

Vehicle VIN: Not present
Vehicle Manufacturer: Unknown
Vehicle Calibration ID: Not present

Test report:
------------------
MID:$01 TID:$81
- O2 Bank 1 Sensor 1
Max: 65,535Count Min: 20Count
Test result value: 32Count
PASS
----
MID:$02 TID:$05
Rich to Lean sensor switch time(calculated) - O2 Bank 1 Sensor 2
Max: 5,900ms Min: 0ms
Test result value: 1,100ms
PASS
----
MID:$02 TID:$08
Maximum sensor Voltage for test cycle(calculated) - O2 Bank 1 Sensor 2
Max: 7.99527V Min: 0.52704V
Test result value: 1.05408V
PASS
----
MID:$02 TID:$82
- O2 Bank 1 Sensor 2
Max: 1.00003V Min: 0.31232V
Test result value: 1.05408V
FAIL
----
MID:$02 TID:$88
- O2 Bank 1 Sensor 2
Max: 500ms Min: 0ms
Test result value: 50ms
PASS
----
MID:$21 TID:$83
- Catalyst Monitor Bank 1
Max: 0.09765Ratio Min: 0Ratio
Test result value: 0Ratio
PASS
----
MID:$35 TID:$89
-
Max: 5° Min: 0°
Test result value: 0.7°
PASS
----
MID:$36 TID:$89
-
Max: 5° Min: 0°
Test result value: 0.05°
PASS
----
MID:$39 TID:$85
-
Max: 766.75946kPa Min: 1.9422kPa
Test result value: 1.9422kPa
PASS
----
MID:$3b TID:$85
- EVAP Monitor (0.090")
Max: 1.8837kPa Min: 0kPa
Test result value: 0kPa
PASS
----
MID:$3c TID:$85
- EVAP Monitor (0.040")
Max: 1.3338kPa Min: 0kPa
Test result value: 0kPa
PASS
----
MID:$a2 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 1 Data
Max: 65,535Count Min: 0Count
Test result value: 1Count
PASS
----
MID:$a2 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 1 Data
Max: 65,535Count Min: 0Count
Test result value: 1Count
PASS
----
MID:$a3 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 2 Data
Max: 65,535Count Min: 0Count
Test result value: 4Count
PASS
----
MID:$a3 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 2 Data
Max: 65,535Count Min: 0Count
Test result value: 1Count
PASS
----
MID:$a4 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 3 Data
Max: 65,535Count Min: 0Count
Test result value: 1Count
PASS
----
MID:$a4 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 3 Data
Max: 65,535Count Min: 0Count
Test result value: 2Count
PASS
----
MID:$a5 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 4 Data
Max: 65,535Count Min: 0Count
Test result value: 44Count
PASS
----
MID:$a5 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 4 Data
Max: 65,535Count Min: 0Count
Test result value: 1Count
PASS
----


End of report.

KingTal0n

I think swap plug wire with another cyl, and the injector next, is a very good start from where you are.

make sure no oil on plug or in cylinder, check with a scope or light or something

kyleegbert

Is it safe to just swap wires between cylinders? Won't they fire at the wrong time? From previous inspections, there was no trace of oil, but i'll look again in a little bit

splattj

iTrader: (2)

I think King meant to swap coil packs between cylinders. Switch the coil packs between #4 and #3 and see if #3 becomes the most prevalent. If so, it's a bad coil pack. And no, you can't just swap the wires and it would change the firing order.

kyleegbert

Oh, i did that, then I outright replaced them :-)

KingTal0n

Oh I don't know the engine. Just general diagnostic procedure is move things from cyl to cyl to see if you can move the issue from one to the next.

I thought you meant regular plug wires. If it has coilpacks, why do you mention plug wires? It must mean something different than it does for normal distributor engines.

splattj

iTrader: (2)

The only other thing I can think of that you haven't mentioned is timing chain stretch. I know it effected the 08-11 Evos before they revised it. When it gets BAD it throws a P0012 code but if yours is just a little bit out of spec it could cause idle issues without throwing a code.....

I'd start with moving the injectors even though it's a hassle and go from there!