Misfires after swapping to Denso plugs

[Knowa]

Hi guys,

Over the last weekend my dad and I swapped my stock plugs out for Denso IHK24s gapped at .22 per BMS recommendation and after running the car for a day or 2, my obd2 reader is saying I am having a couple misfires in Cylinders 2/3/6, with 6 being the most frequent. I haven't installed the JB4 yet so I am still running bone stock with 93 gas. I took a test drive with the reader running and it appears that 90-95%+ of my misfires are in the first 2-3 miles of my drive. Could this be from not letting the car warm up enough before going off on my way? Should I try different gas? Should I take it to the dealer and let them deal with it?

Just trying to figure out what my next steps should be.

Thanks

 

[ChaneRZ]

No. Car should not misfire at all on hot or cold engine. Be sure installation was on point. Be sure the coil packs are seated properly. Buy from reputable dealer. No Amazon orders!

 

[Knowa]

Should I be driving the car at all until we figure out? Would the dealership freak out if I pulled up with non-oem plugs installed?

 

[Terry@BMS]

I'd work on it yourself, maybe gapped wrong, or didn't reinstall something properly.

 

[Intelliburn]

No. Car should not misfire at all on hot or cold engine. Be sure installation was on point. Be sure the coil packs are seated properly. Buy from reputable dealer. No Amazon orders!

Great advice. Noooo Amazon!

 

[Knowa]

No Amazon for coils? I bought my denso's through the forum store.

 

[Intelliburn]

Great advice. Noooo Amazon!

No Amazon for coils? I bought my denso's through the forum store.

For the plugs no Amazon. Double check installation before replacing coils. There are a number of OeM parts sites I’ve used. Kiapartsnow, Genuine oemkiaparts., there may be others: I’d look for coils on one of those sites.

 

[JSolo]

^^Are you thinking bad connection to the coil terminals?

Since cyl's 1, 4, 5 are not misfiring, might be worth a try to swap coils from those the troublesome cyl's. See if the misfires follow the coils¿?

Are the reported misfires cumulative or per that ignition cycle?

 

[Knowa]

^^Are you thinking bad connection to the coil terminals?

Since cyl's 1, 4, 5 are not misfiring, might be worth a try to swap coils from those the troublesome cyl's. See if the misfires follow the coils¿?

Are the reported misfires cumulative or per that ignition cycle?

That is cumulative from when I turn the car on to when I complete my drive. On my most recent test drive (14 miles) it was 9 misfires, 2 on 2, 3 on 3, 4 on 6. 8 occurred on my drive there, 1 was while idling for 2 minutes or so at the destination, none on the drive home.

 

[General_Vodka]

um .22 is kinda low if you are not running the jb4. stock gaps is like 38 ish. check connections to the coil packs, I had misfires but I forgot to plug a coil back in so that was entirely my fault. My suggestion: ditch the densos and go hks. there is like 10 denso complaints for every hks complaint.

 

[Knowa]

um .22 is kinda low if you are not running the jb4. stock gaps is like 38 ish. check connections to the coil packs, I had misfires but I forgot to plug a coil back in so that was entirely my fault. My suggestion: ditch the densos and go hks. there is like 10 denso complaints for every hks complaint.

I imagine trying to run the jb4 on map 1 to see if its just too low of a gap for stock right now is probably not a great idea, right? I might swap to HKS on my next set of plugs assuming these are ok there was just some installation error on our part.

 

[General_Vodka]

I imagine trying to run the jb4 on map 1 to see if its just too low of a gap for stock right now is probably not a great idea, right? I might swap to HKS on my next set of plugs assuming these are ok there was just some installation error on our part.

You don't meet the map 1 requirements?

 

[monusa]

um .22 is kinda low if you are not running the jb4. stock gaps is like 38 ish. check connections to the coil packs, I had misfires but I forgot to plug a coil back in so that was entirely my fault. My suggestion: ditch the densos and go hks. there is like 10 denso complaints for every hks complaint.

I 2nd,3rd what @General_Vodka is saying. if you are not running the jb4 now, that gap is way too close for the stock boost level. either adjust the plugs or go ahead and connect the jb4 (the easier option). Since it appears you are planning on running the jb4 anyway, no use regapping plugs. Start at map 1 and check the logs for the jb4.

 

[monusa]

Map 1 will run on stock plugs(prefer either Denso or HKS) and 91 gas but since you have the Densos already in, connect jb4 and set to map 1. I too am biased to HKS.

 

[Knowa]

You don't meet the map 1 requirements?

Why don't I? I am running gapped densos on 93 gas

 

[General_Vodka]

Why don't I? I am running gapped densos on 93 gas

I was asking if you meet the requirements. I honestly forget what map1 requires. But yeah, if you do meet the requirements then use map one and see if it changes. Then share some logs and the jb4 guys will let you know if something is off.

 

[Knowa]

I'd work on it yourself, maybe gapped wrong, or didn't reinstall something properly.

Could the gapped too small to run the car stock be a plausible theory or would you still recommend pulling the plugs and reinstalling/double checking connections?

 

[General_Vodka]

Could the gapped too small to run the car stock be a plausible theory or would you still recommend pulling the plugs and reinstalling/double checking connections?

if your jb4 is already hooked up then try map. No one I know ran that small of a gap on the stock tune.

 

[monusa]

Could the gapped too small to run the car stock be a plausible theory or would you still recommend pulling the plugs and reinstalling/double checking connections?

this is not really theory......it's all about the combustion process. The reason for the colder plug and smaller gap is that when you are running the jb4 and the boost is increased 4-6 psi over stock, the result is the higher combustion pressure/temperature needs a plug/gap that can fire under those conditions.

Your misfire could be that you are not getting a full burn on the compression stroke due to the gap being too tight for the stock level of boost......plenty of online articles on this.

If you have already installed the Denso plugs, I am curious as to why you have not connected the jb4? Again, per the jb4 "recommendations", with 93 gas, you should be able to run map 1 with no issues and even map2 as long as the logs look good.

 

[Knowa]

If you have already installed the Denso plugs, I am curious as to why you have not connected the jb4? Again, per the jb4 "recommendations", with 93 gas, you should be able to run map 1 with no issues and even map2 as long as the logs look good.

I went on a test drive after installing the plugs but before the jb4 to make sure there wasn't something majorly wrong before trying to push the engine a bit harder with the jb4. Once I saw that it was misfiring, I hesitated on installing the JB4 becuase I didn't know that misfiring could be expected running those plugs without the tune.