Runnin rich...
 

I did the bolt-on mods to my 92 GT and it seems to be running rich now, and the mileage has gone from good to bad. The plugs look good, no soot, and the motor is running strong from idle to 6k. My question is, if I pull out the 24# injectors and put the 19's back in, will it make a difference? Would an adjustable fuel pressure regulator work to limit the amount of fuel going in? Or is it in the computer and needs to be dealt with some other way? Thanks y'all...

Is your MAF calibrated for the 24lb injectors? The reason I ask is because when going from 19 to 24 lb you can get an increase of 20% more fuel. I hav 24lb injectors and was running fine with good gas mileage and my MAF went bad. I went to put on my stock MAF and it is running rich also.

24lb injectors? how many mods do u have? i dont feel that you need 24lb injectors for a car with bolt ons and less u have a blower or nos, what type of cam do u have? What i guess i am trying to say. Do you really need that much gas? its just my opinion though so fill me in.. I have 19lb injectors with almost the same set up i have b303 cam gt40 heads, bbk long tubes, but stock intake, i think u should be fine with a fuel pump, fuel pressure reg...
later

drtbiker - you look like you are ready for an intake with those mods :D You're definately choking your engine.

As for 24lb injectors, he may not need them, but they shouldn't be hurting him either as long as his meter is calibrated for 24lb injectors. An adjustable FPR wouldn't hurt though. I was running pretty much the same setup as Drew is with no problems at all, and 20mpg on the highway with 3.73 gears.

Drew, if you're running rich your plugs shouldn't look fine. Change a plug then go out and drive it at wide open throttle. Pull the plug and see what you have then. If it's black you are running rich. Check your vacuum with a tester to see where it's at. How do your brakes feel? If you pull up to a stop and let off the brake pedal and depress it again with the car idling does the pedal feel harder than it should? Does the car have any sputtering anywhere in the RPM range while holding the car at a constant speed?

When I first installed my mods I was getting 9" of vacuum. Not good. After finding the problem I was running 15" of vacuum and the car ran great.

isn't a normal vaccuum reading at idle supposed to be around 24 lbs?

24lbs would be astronomical. Vacuum in an internal combustion engine is measured in inches. I'm not sure what the reading should be on a stock 5.0, but it will vary depending on the cam, intake, TB/EGR spacer, etc. My car ran great with 15 inches and the brakes worked like they were supposed to. A lot of my friends that have ran the F303 cam said they had 15 inches of vacuum as well.

my bad... i just read through the old posts and found my mistake... 15 is good... my stock 5.0 w/ just a set of pulleys on it runs 18 at idle.

Everything is working fine actually, I think I need to get an air/fuel ratio meter and check the results. That and a vacuum gauge. I really appreciate y'alls responses, I'll post what I find out!

Drew

When I had my EFI car I had similar problems. When I would mash it though, black smoke would roar like crazy. Also it would buck and surge. At idle it was richer than crazy.

I installed a adj. fuel pressure regulator (from stock) and cleaned my throttle body and it fixed everything. I think it was the regulator. It was amazing the difference it made. I would get one if you have not already.

adjustable FPR...
 

I have to agree with the above posts...
24# injectors are a bit too much for cars w/o aftermarket heads.
I personally run at 35 PSI and it is still a tad rich.