420A Misfire At Idle (Megasquirt)

[95TalonOwner]

Hey guys.

My car is running good and things are going well but I have this pesky misfire right around 1100-1200 rpm. It only happens at that rpm with 0% throttle. If I turn my radiator fans on or lights on to load the engine down a bit, the rpms drop to about 800-900 and the idle is fine. This is really stumping me.

The link below leads to my log file which can be viewed with megalog viewer and I also have a video to show you what I'm talking about.


missfire.msl

2AC97BE5-A3E8-4782-8C54-8A6397100DDA-9540-000009AB44BA01BE_zps33bc8769.mp4

 

[silvreclips]

Ill have to check out the log when I get home but the car doesnt sound bad. Sounds just like a little lope from the cams in the car. Maybe the cams need to be degreed in?

 

[95TalonOwner]

Cams are zero'd with a dcr tool. Video doesn't do it justice. It is definitely falling into a miss and not just a lope. I did not have this problem a couple years ago with these cams. Just seems a little weird.

 

[silvreclips]

I havent had a chance to look at the log yet, are you running batch fire or sequential injection on the car?

 

[95TalonOwner]

Batch.

I looked into it a little further last night and when it is missing, I can take #1 or 4 spark plug wires off and there is no change in the way the engine sounds or runs. There is spark in those cylinders. I wonder if it has something to do with the injector driver for those cylinders.

 

[silvreclips]

Couple of things that will probably help you out, you need to tune for 13.5-14.0 AFR at idle with batch fire setups. You will always get some fuel injecting at the wrong time with that setup so you need to tune a bit richer at idle. Change your target AFR as well. Also the stock ECU runs fairly low timing at idle I around 5-10* at idle. You could try lowering your timing as well. It also may help you turn off your EGO correction while trying to stabilize the idle.

 

[95TalonOwner]

I played with the timing at idle and nothing changed it. It seems happy where it is now. I did add some fuel at idle but nothing really changed there besides the AFR's.

Here is another log where the engine is "surging". Also only happens at very light throttle in the same rpm range as the misfire.

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Also, here is another log of driving a bit. It also has the surge in it along with the misfire towards the end.

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And another file with mainly just misfire.

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I'm starting to think something mechanical with the injector(s) or something with the MS itself.

 

[jayson427]

I'm not up to par with Ms but would swapping out to another stock ecu help at all? I had one cylinder running leaner then the others. The stock ecu was the culprit and it went away after I changed ecu's I guess there was an issue with my injector driver. Hopefully you figure it out soon.

 

[95TalonOwner]

I do not have a stock ecu.

 

[LeeSD1]

I had the same problem. Turned out to be the ignition coils. Megasquirt ecu was running normal and trying to spark but no spark was at the spark plugs. to determine if that's the problem use the Test Mode feature in Tunerstudios to test for spark.

 

[95TalonOwner]

I had the same problem. Turned out to be the ignition coils. Megasquirt ecu was running normal and trying to spark but no spark was at the spark plugs. to determine if that's the problem use the Test Mode feature in Tunerstudios to test for spark.

I tested and swapped coils with a few others I had laying around and I do have spark so it must be injector related.

 

[LeeSD1]

have you tested them in the test mode?

 

[VelocitàPaola]

have you tested them in the test mode?

I agree, that'll be the best way to rule out the injectors or the injector drivers.

 

[95TalonOwner]

I agree, that'll be the best way to rule out the injectors or the injector drivers.

I hope to get around to that later today or tomorrow. I was going to do it yesterday but left my laptop at home when I went to my shop.