Recently I pulled my injectors to replace the o-rings. I was pretty sure that I had an injector that was leaking a little oil by an o-ring because of these symptoms:
I had a rough idle when the engine is up to temp. When the engine is cold it would idle silky smooth. One of my chip positions has a 600 RPM idle and it was much more noticeably rough idling than the rest of the positons which have a 750 RPM idle. At the 600 RPM idle I even had some problems with the engine stalling when I was slowing down to a stop or slowed down to turn a corner. If I revved the engine up to 2000 RPM (trans in neurtal or park) and let off the pedal quickly the engine would stall 95% of the time when the engine was warm but when cold it would return to idle perfectly.
--All of these symptoms started the day that I removed my stage 1 injectors and installed the B-codes. I bought the B-codes used and the o-rings looked good on them so I just decided to save my 50 bucks and reused the o-rings. Also it is note worthy to say that I saw absolutely no change in this condition when I went from a stock HPOP
to the Stealth (dual IPR
After dealing with these issues for a few months I finally decided to pull the injectors out and put new o-rings on them. While changing the o-rings I didn't find any of them that I thought were real bad, but there were one or two of the square cut o-rings that were a little suspicious looking.
I got everything back together and running last night but much to my displeasure my choppy idle when warm remained...I was more than a little peved to say the least
After I was done test driving, and I cooled off a little, I decided to try messing with my fuel pressure some and see if that helped any. I have been running 65 psi
so I backed it off to about 55 psi
and saw no change. So I backed it down a little more to about 48 psi
and what do you know it doesn't stall every
time you let off the accelerator at 2000 RPM in neutral, but it still struggled to stay running. So now I figure lets try it a little lower and go to 35 psi
. Now the truck idles pretty much like any stock PSD
(you know they aint quiet) and I can not
get it too stall when revving the engine to 2000 RPM and letting off the accelerator quickly. I probably tried 20 times and every time it came to an idle effortlessly, and this is in my 600 RPM idle program.
I am somewhat at a loss at how higher fuel pressure can cause a rough or choppy idle only
when the engine is warm but I guess you don't have to understand it if you know it works. I was so 100% sure I had an oil side problem whether it be o-rings or within the injectors them selves but it turns out to be fuel pressure
Also even more confusing is that the stage 1 injectors idled perfectly and didn't have any stall issues with the constant 55 to 65 psi
of fuel pressure.
What I plan to do about this issue is to run about 35 to 37 psi
fuel pressure at idle and hook my boost reference port on the fuel pressure regulator to the regulated side of my ITP Overboost Annihilator. That should get me to 55 psi
of fuel pressure any time I am at 20 psi
or higher boost. This will probably extend fuel pump life as well I would imagine since most of the time I am under 15 psi
boost cruising down the road.
Long (extremely long) story short, if you have some idle irregularities it may be a good idea to try a fairly low fuel pressure to see if that cures it. Especially before pulling injectors to replace o-rings or sending them back to the builder. My next step was going to be to send them all out to have bench tested because CCT would not show me any problems with a specific cylinder.
Oh, I would like to give props where they are deserved. Thanks to Geoff (aka GTSMotorsports aka Hot Wheels) for recommending that I try some extremely low fuel pressure to cure it. He has to run about the same pressure as I am to cure some idle issues on his truck.