Recently finished installing 555cc injectors - now have an issue witht he Z running poorly. If you give it a blip - it will stumble and hesitate very badly at around 3000rpm When driving it won't pull smoothly. Swapped FPR - no change. Bought a fuel pressure gauge - 42psi with the vacuum line unplugged - when driving its going up and down depending on boost/vacuum No significant boost leaks IACV/AAC all operating fine (one of the other things I touched while the plenum was off) No error codes The injectors were checked/cleaned by Dwight - all seemed good. I found that by adding 20% extra fuel via ECUtalk - it runs better?
From what I've read (and remember) you need to alter tune and something to do with duty cycle when changing injectors. Should be someone who can expand on this.
you need a tune able ecu of some sort because the computer dosent know youve swapped the injectors, you need to tell it be changing the 'K' value and some other settings, its sending a certain volt for a certain amount of time to what it thinks is a 340cc injector but there 555's installed that time needs to shortened Eg. 340cc open for 0.5 seconds 20cc of fuel injected 555cc open for 0.5 seconds 38cc of fuel injected (random numbers nothing will line up) the computer controls the time and needs to know the injectors have been changed so it can shorten the time like 555cc oipen for 0.3 seconds 20cc fuel injected. This has been simplified greatly. Joe
Yes, you need a new chip with the K value changed. Seems odd that adding MORE fuel makes it run better. You have Nistune right?
well if that's the case i would recommend taking it to a workshop and get then to stick a gas analyser up the tail pipe, manly because the 20% extra fuel fixing sounds concerning my be running lean which can be extremely bad, could be a bad tune? has it run right since the injector swap?
Good advice there, Larlock Also check for vac leaks first. Don't be redlining it until you have eliminated incorrect air/fuel ratios.
All sorted now Seems that the chip might have taken a bit of a zap which scrambled some of the data - put the new chip in this afternoon - and its running fine again..... Thanks all for the help!
