82 misfires over a 15 minute ride

[Azotara15]

This morning my car was stalling and misfiring enough where it was noticable under light acceleration, I didn't go over 50% throttle at all but the problem seemed to be when it was cold still.

I warmed the car up for 15 minutes and drove it after that, which is where the misfires started and when I plugged in the accessport it ready 30 already when I left the driveway. Over the course of driving to work it accumulated 82 and was stuttering a lot. I have a feeling it's spark plugs but I want to be sure before I replace parts.

The car is tuned for 93 currently and has 99.5k on the clock so it seems right and there is no check engine light.

I really wish I had the forthought to turn on the data logger but it was 0530 and I wasn't thinking completely clear yet.

 

[FiestaSTdude]

This morning my car was stalling and misfiring enough where it was noticable under light acceleration, I didn't go over 50% throttle at all but the problem seemed to be when it was cold still.

I warmed the car up for 15 minutes and drove it after that, which is where the misfires started and when I plugged in the accessport it ready 30 already when I left the driveway. Over the course of driving to work it accumulated 82 and was stuttering a lot. I have a feeling it's spark plugs but I want to be sure before I replace parts.

The car is tuned for 93 currently and has 99.5k on the clock so it seems right and there is no check engine light.

I really wish I had the forthought to turn on the data logger but it was 0530 and I wasn't thinking completely clear yet.

Plugs are cheap and easy to change, so I'd recommend that you just go ahead and swap them out. When was the last time that you changed them?

 

[Azotara15]

Plugs are cheap and easy to change, so I'd recommend that you just go ahead and swap them out. When was the last time that you changed them?

I believe they are the factory plugs

 

[XR650R]

I believe they are the factory plugs

Time for some new ones. Be sure to gap them how your tuner specifies.

 

[FiestaSTdude]

Time for some new ones. Be sure to gap them how your tuner specifies.

Hopefully this thread from when I did mine will be helpful.
https://www.fiestastforum.com/threads/changing-spark-plugs.28259/

 

[Azotara15]

Hopefully this thread from when I did mine will be helpful.
https://www.fiestastforum.com/threads/changing-spark-plugs.28259/

I wanted to go a step colder so I need to find the plugs I need, I also have an e30 tube so the tuner recommended those as well. That forum is a good reference though!

 

[FiestaSTdude]

I think NGK 6510 is what you want. NGK 6509 is the stock heat level if I recall correctly.

 

[XR650R]

I wanted to go a step colder so I need to find the plugs I need, I also have an e30 tube so the tuner recommended those as well. That forum is a good reference though!

If that's what your tuner says, do it.

 

[M-Sport fan]

Time for some new ones. Be sure to gap them how your tuner specifies.

Also, aftermarket tunes tend to 'eat' plugs at a faster rate than the factory tune, so yeah, at 100K miles it is most definitely time.

 

[Azotara15]

Update:

I replaced the spark plugs with colder ones and gapped to .026 as was recommended by stratified (the tuner I went with) and everything seemed to be running fine at first.

I ran the car for about 10 minutes to warm up and no notable knocking or misfires we're detected out of normal range (as some misfires will happen normally)

I drove the car for about 15-20 miles testing it from low acceleration to more modest acceleration (within the speed limit) and for the first half of the trip the car preformed as it should, but later in the test drive it started to give some warning signs that it was not entirely fixed.

Around 2500-3500 rpm the stuttering came back, although not as bad.

Light throttle inputs were more likely to cause misfires than heavy throttle inputs

At one stop light at idle (1000 rpm) the misfires we're happening between 1-2 per second, going from 10 for the previous driving to 30 in about 10 seconds.

All I have done is replace the spark plugs so far, and I'm not too sure how to test the coil packs.

For context on what's modified: intercooler+ piping, tune for e30&93 with boost hitting 29.5lbs on the stock turbo, lightweight flywheel, suspension and wheels. Other than the tune the engine is basically stock and it seems like all the parts are oem as the plugs were from Ford themselves.


The old plugs: they actually looked really good, burning but not black and gapped at .032 all around. They look really healthy coming out but I did put in colder ones and the new ones are iridium.

AFR on the car is usually at 41.42 while driving, under decel closer to 15 or maybe a little higher.

I data logged about half the trip as I made a few stops and sadly I was not data logging at the time of the misfires at the stop light. I did log after I got back and just let it idle for a few minutes while I was watching it and while I brought it up slowly to 2000 and 3000. But no serious misfires while I was logging, of course.