ok well were tuning the truck after the tvs 1900, and is going very well except for the 1800 - 1900 rpm range the truck wants to sputter and run allittle more lean even after commanding more fuel. it runs great @1700 and @2000... we then noticed that in that range the fuel pressure gauge goes ape **** and bounces around real crazy. anyone seen and/or knows a fix for the problem? only things ive changed with the fuel is: went from 42# inj to 60# inj.

 

Strange. Does it do it in that rpm range at any map? Maybe the problem lies with in a certain map range and not rpm specific, and you haven't logged enough time on it to notice. See if you can go back and compare a tune that worked with the one you have now and make sure you didn't make some drastic change you didn't mean to make, like having some ridiculous number in the VE table or injector tables around that rpm or map range. Doesn't sound like a mechanical issue to me if it's fine before 1700 and after 2000. Does it pull fine up in the higher rpms?

Let us know if you get it figured out.

 

checked eveything out and all looked ok the only thing that was drastically changed was where we comanded more in the pids (air/fuel), but had to at that particular rpm range to smoothen it out some. tommorrow im going to check the vaccum line to my fpr, swap to the walbro intank, and all so see if putting a rubber hose to the fuel line may act as a pulsation dampner to smooth it out... really out of ideas other than that. all the other rpms are great the truck pulls so hard and smooth other than this...

ill definitly let you know what it was if i ever figure it out... lmao. i guess i just find it hard that noone has had this same problem... i always seem to have wierd issues...

 

Check or replace the maf.
Lower PE table to 20per or so. Maybe it's having an issue transitioning.

Good luck

 

Good call Allen, now that you mention it I was tuning a transam that had a stumble in that same rpm range. Threw it in SD and car ran perfect. Bad MAF

 

im running sd no maf on the truck...

 

try to bring in PE sooner then, before 100kpa is reached.
or richen the lower rpm hi kpa cells up quite a bit, sounds like a lean condition.

just a thought, could be something.

 

How does it do if you roll into the throttle versus stabbing the throttle? Or is it a more steady state issue?

 

thanks allen. thats right it does run lean there. we already did that, and set to be so much so much richer there and still getting a 15.5 : 1 afr in that rpm range... crazy i know...


the only time you will notice it is if you roll into the throttle, because it winds up so freaking fast if you step on it with 50% or more throttle. youll also see it iff your cruising dont the road and going to about 35 - 40 mph and have to feather the throttle to stay at speed.

 

Do you own efi live? If so post up your tune it may help diagnose the issue faster