Hey guys,

My car has 272/272 cams, pulls about 12lbs of vac at idle, and boosts about 28psi on the stock turbo. I recently changed the spark plugs for the first time since I got it and got the identically same plugs (Denso bkh24)...

The car ran great for most of the first day I changed the plugs, and then in the evening and since then (yesterday) it has been breaking up at about 13-16psi no matter how much throttle I give it. The car still idles and drives great otherwise. I made sure all my vacuum lines looked good and made sure all of my ic piping was well tightened down.

Only thing I can think is maybe the gap isn't right on the plugs??? Any recommendations on what gap I should run on those plugs on an evo ix? My mode are in my Sig.... thanks!

 

BTW.. current gap is .028 inches. Not sure that u are supposed to regap iridiums though...

Any thoughts or recommendations are much appreciated though.

 

I gapped mine to .025 since they tend to widen slightly over time, .028 isn't much wider so I'm not sure if the little difference can cause it to break up. My car was breaking up and found out my plugs were at like .036 lol

 

Chris @ AMS tapped mine down to .020 on stock coils to eliminate my break up. I would suggest maybe .025 see if that helps and then go tighter if necessary.

 

If you mean its sputtering at that boost, it could be that your running rich also. I just got my car tuned yesterday and before I got tuned I was running rich as hell and kept hitting fuel cut. My NGK's are gapped to 22 so try regaping them and that might fix it also.

 

Thanks for the input guys. I am going to pickup a wide-band later this week, but I'm hoping that's all the problem is - spark getting blown out, and re-gapping will resolve the issue. I'm going to also do a boost-leak test today or tomorrow at my buddy's house. My guess is that this isn't the problem though- just want to cover my bases.

Anyhow, thanks again everyone!

 

No problem.

 

I have a similar setup and I'm gapped at .022 without issue.

 

https://www.evolutionm.net/forums/ev...ead-plugs.html

 

If it sounds like a machine gun when at higher boost your turbo is blowing out the spark before the fuel gets to it. To fix that you need a smaller gap or you have the wrong pugs!

 

cfdfireman1- good thread I had been looking for something like that, Im running the BPR8ES at .22. Currently pushing 27 lbs and havent had a problem. I heard Ill be fine but gotta change them out every oil change wich is fine since theyre like 8 bucks.

 

I was told you are NOT supposed to gap iridium plugs...doing so will damage/remove the small amounts of iridium/platinum causing your car to not run right.

Someone else on here can confirm/deny what I've heard.

 

Update: I gapped the plugs down to .022" and it did help some, but still breaking up. I had my buddy do a few datalogs on some 4th gear pulls from 2500RPM's to redline, and where I'm seeing the hesitation the car is hitting 2-3 counts of knock.

I've been waiting to order a wideband, but I'm going to now. I think the car is more than rich, and if anything, it's too much fuel that is causing the issue, but the odd thing is, I've been on this tune for the past 6mo that I've had the car and however long the previous owner had it, and it's been GREAT!

Only thing I did was replace the spark plugs this week with the exact same plugs (BKH24) and it was fine for most of the day... I was doing a 4th-gear pull and it seemed to load up with fuel and blew out a huge black cloud of smoke. Since then it's been breaking up only under mid-boost. No CEL's, no nothing. Dunno...

 

I thought you said you were running iridium plugs, these would be coppers, which can be regapped. Iridiums would also be much more expensive. Just wanted to clarify which plugs you are running.

Edit: mixed up the posters...sorry! Disregard!

 

lol. np... yeah, running BKH24 Iridiums.