I'm having a really annoying hesitation / spark cut / spark blow out between 3800rpm/5000rpm only when 50/60% throttle / 5/15psi.

Before 3800/4000 rpm no problem, after 5000 rpm no problem. If I go WOT no problem, little throttle cruising no problem.

Car was email tuned a while back, and this problem started happening not long ago.

I got the injectors tested and cleaned, they were ok.

Changed spark plugs, got better but still happened, switched back to stock coils (I was running COP spooling up kit) same thing, back to COP now.

Closed the gap on the spark plugs, same thing. Changed again spark plugs, now to iridiums since I think coppers could have gone bad really fast, same thing.

I log TPS, timing, injector duty cycle, AFR, battery and everything seems to be ok, no sudden changes, nothing.

What could this be?

Thanks for your help

 

Could be a boost leak

 

It'll be running too rich when it starts to misfire.

Take a look at the sparkplugs.

photos?

 

This are the coppers I had before runinng new Iridiums I have now, wideband doesnt shows a full rich situation


Will test for boost leaks

 

Gap looks a little to small, try .022-.024 Helped my similar situation alot

 

they were gapped at 24 and then regapped at 20/18 just to see if it was a gap issue

new iridiums are at .22/.24 and same thing

I'm thinking it could be methanol injection related, I will turn it off to see if it helps

 

It's obviously another AFR problem.

Too rich at low load, lean at high load.


Another bad tune.

 

is it possible for a tune to go bad over time?

 

I think "theoretically" possible. A boost leak is a good tune going bad over time. Worn or failing injectors, fuel pump, dirty air flow sensor, etc. Nice thing is if restored, tune should be good again with ecu reset.
I wonder if OP has leaky throttlebody seals where full throttle position leaks boost less than partial. Or bad injectors?

 

To me, black is rich but ceramic looks like it ran lean. But not necessarily a bad tune (since it ran fine when tuned). It could be injectors needing service or replacement, or non-linear boost leak. I think boost leak test is good start. Definitely regap spark plugs since it looks too tight.

 

Which cylinder had the completely black spark plug? Could try swapping that Injector with one of the others to see if black spark plug follows

 

You haven't listed all the mods.

Probably a bigger pump in there somewhere?




Tunes don't change but email tunes are never right and parts break due to bad tunes, so the end result can easily change over time.

 

Mods are stroker 2.3 motor, fp black, walbro 255, precision 1200 injectors, intercooler, pipes, intake, exhaust, header, S2 cams and springs, water methanol injection.

I just took the plugs out and took new pictures, and reprogrammed the water/meth injection (I think is where the problem could be, too much at half throttle)

Here is where I serviced the injectors, they were all the same, and good, and still put new filters on.



Sparkplug 1


Sparkplug 2


Sparkplug 3


Sparkplug 4


In order cylinder 4-3-2-1


1 and 2 seems to be more black than the others 3 and 4

 

You need to fit a fuel pressure gauge.......just like everyone else with fuel problems caused by swapping the pump.

 

OP, can you post the logs that you recorded?