RyanSG said:
i knwo it sounds stupid, but why can't you just adjust the screw on the TB? or does that throw a whole bunch of other things off as well? I also have the same prob, i just added the 76mm MAFS, 30lbinjectors, and a adj FPR. I'm also not sure as to whree to set the fuel pressure, its at like 35 right now and it runs way rich. the air fuel also dosn't swing like it used to b4 the injectors, and i get a 3-400rpm surge it goes from like 500rpm to 1000 and just goes back and forth with the airfuel on the rich side. i'm not sure as to what to do. just play with stuff????
A couple of things you could try:
Simply adjusting the screw on the TB does allow more air into the system and raise the idle, BUT it throws off the TPS settings which should be around 0.96-0.99v when the TB is in a closed position. The TPS voltage can significantly effect idle and drivability. That said, one should try to fix the problem at hand, so that the TB can be in the closed position at idle and have the proper TPS voltage.
One of the main reasons for surging is that it can't get enough air with the TB in the closed position...especially after H/C/I swaps. Often times it is that the IAB isn't allowing enough air into the system, whether it isn't funtioning properly, it's gummed up with crud, OR you just need an idle air adjustment plate installed between your IAB and TB. The later, probably your best bet assuming your IAB is working properly. This situation is typically most prevalent during cold-start/idle.
Once warmed up, assuming all your sensors (ECT, ACT, EGR, O2 and so on) and your computer is working correctly, the computer will adjust the fuel injector duty cycle up and down to maintain the proper air/fuel ratio. So, often times fuel pressure settings have little to do with air/fuel ratio at warm idle, unless the setting is way too low (lean) or the injectors are too large (rich). Fuel pressure setting is however, critical at WOT, especially when tuning for maximum power. If the engine is running a little rich during cold-idle, it is supposed to (within reason). If it is running rich during warm idle, then it MAY be you are using too large of an injector. However, before swapping injectors, make sure everything else is working properly.
The 76mm MAF. If it is a C&L unit (I am running the same), then I have found that these sensors are really sensitive to resonance issues and need to be protected from fan wash. I created a sheet aluminum piece that covers my airfilter and MAF. It was a significant difference and really smoothed out the idle and cruise operations.
Another thing. If you are using a cone-style air filter (
K&N, or the like) you have make sure that the air filter outlet is at least 76mm ID, as well. If you have somehow put on a filter that was designed for a stock 5.0L, it has a 53mm ID outlet and may be creating flow eddies as the air moves from a small conduit to a large conduit...which the MAF senses and creates some erratic behavior with the engine. I made this mistake, as well.
I had to take a razorblade knife to the end of my filter to make it fit over my MAF. Anderson Ford Motorsport sells filters with larger openings, as well.
In the end, custom computer tuning is something that I highly recommend for any engine that has received significant mods. Make sure that cold-idle, cold-start, warm-idle, cruise, WOT, etc. operations get addressed with the tuning. They'll have it on the dyno several times with a wide-band O2 sensor installed just past the headers and a laptop plugged into your computer. Plan on the tuner having it for at least a few days to work out any "bugs" and allow for the computer to learn the new settings before you pick it up.
Just me....
