Hondata

ive been running the car on my new tune since july had a few track days all went perfect with the car... driving on the week ends spot on with no issues

recently the car started to miss fire around the low rpms and running very lean, around 2000rpm and up, af ratio was showing around 1.20/17.5 on the tables.
the AF sometimes goes to its normal values around 12-13 once warm up but has a rough idle like it wants to stall.... and continues to miss fire.
doesnt wanto to start straight away either now usually takes a few cranks.

i thought the issue could be a map sensor so ive checked continuity along with voltage to both the ecu and the sensor, along with vacuum testing it, all checked out.
ive checked all the earth points on the car and have cleaned the contact points.

the previous week before my issues started i replaced my spark plus and leads. i was originally using ngkr8eix-11 i switched to 7 heat range now with ngk leads again.
went out for a long drive and all was ok, parked the car in the garage, and the follow week this issue started..

im really stuck what to try next, ive checked for any vacuum leaks also and still cant find the problem.

could it maybe be the spark plugs? should i put iridium 8's back in?


the car is an ek9 facelift type R hondata s300 v3
b18c type r motor
550cc grams injectors
ngk blue silicon leads
ngk bkr7eix-11 plugs
stock map sensor
12.1 compression ratio
skunk2 pro1 cams

please help!!! :(

Are you using resistor or non-resistor type spark plugs?

the ones im currently running in the car are BKR7EIX-11 iridium i drove the car with these for a about 1 hour..

the following weekend the car developed the problems.

previously i was running BKR8EIX iridium and the 8's is what the car is tuned on.

would this be the issue? not sure if these are resistance plugs... doesnt the ''R'' mean these are the resistance type?

i have made a datalog with the heat range 8 plugs back in... the data file is just over 10mb wont let me upload is there anyway of sending this to you to have a look at? the car seems to run ok with the BKR8EIX, when first started it runs very lean then the numbers change back down to around 13 in the the fuel table once the car begins to come up to temperature.

This could be a problem with loss of compression, bent valve, leaking valve or any other mechanical issue. You should do a leak down and compression test first.

after monitoring the car withe the BKR8EIX, the car seems to run how it did before no issues. took it around the block and the power seems to be there no issues. im guessing the car did not like the BKR7EIX-11 for what ever reason???

i have taken a data log of the car starting up and idling with BKR8EIX plugs, at first for 2-3 mins the car was very lean then the numbers come tumbling down on the lambda reading page. starts around 1.20 then drops progressively to 0.81~

is this normal?? as i havent tuned the car myself and ive only just noticed this since i was trying to fault find my missfire issue with the BKR7EIX-11 plugs. the car was tuned by a well known company in a dyno cell room.

i have attached data logs showing various points from idle to af dropping to normal and at operating temp and one with alittle throttle here and there.

id appreciate some input and advice

thank you

I highly recommend that you discuss this issue with your tuner as they will be able to give the best feedback on what could be a mechanical issue or a tuning related issue.