Slight miss/blip at idle

[bsbllfit7]

My car is mostly all stock right now minus an intake and exhaust. I am having a very slight miss at idle, doesn't really affect the car as much as you can just hear it blip through the exhaust. I have done a BLT and came back with no leaks. New spark plugs have been thrown in to no avail. I did gap them down to .25 because .28 was missing more rapidly. Im wondering if maybe this is transistor related or coil pack related. What are your guys thoughts on this, and yes i have searched but no one seems to have the identical situation that I am having.

 

[foxracing4500]

My car is mostly all stock right now minus an intake and exhaust. I am having a very slight miss at idle, doesn't really affect the car as much as you can just hear it blip through the exhaust. I have done a BLT and came back with no leaks. New spark plugs have been thrown in to no avail. I did gap them down to .25 because .28 was missing more rapidly. Im wondering if maybe this is transistor related or coil pack related. What are your guys thoughts on this, and yes i have searched but no one seems to have the identical situation that I am having.

I think we have the same thing? do you have a wideband? when it sounds like it misses does your AFR hit anywhere near 15 for a split second? I dont know the answer yet to my problem but it sounds very similar.

also wanna toss this out for DSM wisemen, ceddy mods - Max dwell time all latency's are 6.144, when my blip/miss occures I see dwell times like 6.833 is that a problem?

 

[Mitsubishigst1999]

Since you already replaced the plugs try replacing the coil packs and go with a MSD 8.5mm wire set mabye get better spark.

 

[bsbllfit7]

Happened on my old car as well, i did have a wideband and when i did it would lean out temporarily for the duration of the blip. Come to think of it i did use these exact spark plug wires on the old car. Hmm wonder if its something as simple as that.

 

[Spoolin92GSX]

I have almost the identical thing happening on my car. Very irritating for me since I'm self-tuned and it looks like a tuning error to others. I'm locked open loop also, and see a lean blip when it stumbles. I doubt it's plugs or wires, I'm running month old NGK wires and BR7ES's gapped to .020" and no other spark related issues. I would love to figure this out though.. BTW since I'm on speed density we can eliminate MAF and o2 sensor problems, and my ECU was recently overhauled by ECMTuning. TBH I'm suspecting an issue in the ISC and/or FIAV, I'm considering picking up a spare throttle body just to block those off and see if anything happens.

 

[bsbllfit7]

I unplugged the isc to see if the problem persisted and it did. ISC should not be the problem atleast in my case.

 

[undefined0000]

I have almost the identical thing happening on my car. Very irritating for me since I'm self-tuned and it looks like a tuning error to others. I'm locked open loop also, and see a lean blip when it stumbles. I doubt it's plugs or wires, I'm running month old NGK wires and BR7ES's gapped to .020" and no other spark related issues. I would love to figure this out though.. BTW since I'm on speed density we can eliminate MAF and o2 sensor problems, and my ECU was recently overhauled by ECMTuning. TBH I'm suspecting an issue in the ISC and/or FIAV, I'm considering picking up a spare throttle body just to block those off and see if anything happens.

Let me know how that works out for you. I've got it too. Just sounds like a random miss. Only happens after the car is warmed up though. I just ignore it and it lets me know when I can start driving it in the morning. Not sure what the AFR is when it happens, but I will find out as soon as my uego gets here!

 

[Calan]

If you eliminate everything in the ignition, it's most likely due to mismatched injector latency (dead time for you ECMLink guys). Small fluctuations in injector voltage can also cause it; the voltage-based latency tables are never completely accurate, and each injector behaves a little differently. Since injector latency has a larger impact at low airflow (short injector pulse widths), these types of misfires usually show up at idle and light cruising.

Another possible cause is temporary fouling of the plug, due to the plug being to cold (especially with E85). If you are running something colder than the stock BPR6ES plugs, try a plug that is one step hotter and see if the misfire goes away. The hotter plugs will hold more heat between sparks, which helps burn away small deposits that can cause misfires. Unfortunately, they are also more likely to cause detonation issues...so you have to find a good balance.

Also note that the lean spike could be either the cause or a result of the misfire. A misfire causes an excess of air (oxygen) in the exhaust, which registers as a lean condition. Likewise, if the AFR momentarily goes lean for some reason, a misfire can happen due to there not being enough fuel in the spark gap.

 

[Spoolin92GSX]

I unplugged the isc to see if the problem persisted and it did. ISC should not be the problem atleast in my case.

Not necessarily the ISC being bad/not working, but occasionally internal leaks can happen mainly in the FIAV.

If you eliminate everything in the ignition, it's most likely due to mismatched injector latency (dead time for you ECMLink guys). Small fluctuations in injector voltage can also cause it; the voltage-based latency tables are never completely accurate, and each injector behaves a little differently. Since injector latency has a larger impact at low airflow (short injector pulse widths), these types of misfires usually show up at idle and light cruising.

Another possible cause is temporary fouling of the plug, due to the plug being to cold (especially with E85). If you are running something colder than the stock BPR6ES plugs, try a plug that is one step hotter and see if the misfire goes away. The hotter plugs will hold more heat between sparks, which helps burn away small deposits that can cause misfires. Unfortunately, they are also more likely to cause detonation issues...so you have to find a good balance.

Also note that the lean spike could be either the cause or a result of the misfire. A misfire causes an excess of air (oxygen) in the exhaust, which registers as a lean condition. Likewise, if the AFR momentarily goes lean for some reason, a misfire can happen due to there not being enough fuel in the spark gap.

I thought about fuel delivery too, even though logged voltage stays between 13.4-13.8. I understand the "stock" ECU code uses interpolation, you think that would be enough of a range to pull the "off" latency value into play?

 

[Calan]

you think that would be enough of a range to pull the "off" latency value into play?

What do you mean by the "off" latency value? Are you talking about the closing delay of the injector?

If so, the amount of time it takes for the injector to close is pretty insignificant compared to the opening time, and I'm not really sure how that would come into play as far as misfires go.

 

[Spoolin92GSX]

What do you mean by the "off" latency value? Are you talking about the closing delay of the injector?

If so, the amount of time it takes for the injector to close is pretty insignificant compared to the opening time, and I'm not really sure how that would come into play as far as misfires go.

Sorry, the particular voltage cell that may be incorrect. After watching my wideband VERY closely, it seems the lean spot happens ever so instantly after the actual miss though, so I'm now suspecting an ignition related miss.