Mylittlepony95

Hello all, I have a 95 mustang GT with a rebuilt 5.0 in it that has the comp cam magnum 35-308-8 and gt40p heads. It has stock 19Ib injectors, stock MAF, stock EEC but I do have a moates quarterhorse to tune it. The car bogs down and dies when switching gears from reverse to drive or vice versa. In neutral the idol hangs at 1,000 rpm when giving it gas, the acceleration seems to bog down before it goes when i step on the gas hard. And I've read that these cars can be smelly, but personally i think the exhaust from mine is hella rich more than it should be. I think I have a fuel injection problem, and I have no clue where to go from here or what my next steps should be. Could this be any other kind of problem? Practically everything on the car is brand new. Where do I go from here? Thanks.

Pic so you can see how much detail I've put in this sucker, and so far it feels like for nothing because I can't seem to get the darn thing to run right!

Buck Sergeant

LittlePony, check this out. 19's - Orange
24's- light blue
30's- Red
36's- Dark blue
38's are Lucas only and are black
42's- Lime Green
42's Lucas are black with a green band

With the "Comp Cam", and "GT40p" heads, I would suggest going with a larger fuel injector, even if that isn't the immediate problem. Probably 24s, maybe 30s.

Buy the way, very clean package. Looking good.

dawson1112

Your not even making enough power to use 75% of what those injectors are rated at. 19lbs is fine.

I would look for a vacuum leak someplace. Run the koeo/koer diagnostics tests and record any codes. It could also be a faulty 02 sensor.

wbrockstar

The chart at the bottom will give you a max hp rating for each injector listed,which you wouldnt wanna run them at because thats their rating at 100% duty cycle at 40psi,so lower that hp# by 20-30 so that the injector can be ran at a 85-90% duty cycle.Example:
19lb inj are rated at a max of 304hp @ 40psi,so dropping that number to 275hp is a good safe power level to go by.So if you were making 275hp max at the motor,19lb injectors would work fine.GT40p heads,GT40 intake,cam & oem 70mm maf wont put you at/above 275hp,so it wont hurt to leave the 19lbrs in with your current mods.(94-95 GT's=215hp stock) If you have plans for adding a much nicer set of heads,exhaust,nitrous,etc in the near future,24lbrs can be added,if you account for them in the tune.The 93/95 Cobra only had 245/240hp & that included GT40 heads & intake,1.7 rockers(.030" increase in lift vs 1.6) oem 70mm maf,24lb injectors.

The suggestion to run koeo/koer tests is good because the cel doesnt have to be on in order for codes to be present and you dont need a scanner to run them either.The link below will show you how.If a code is present,it may tell you exactly whats wrong,without you having to dive into the motor for trouble shooting.

Vacuum leaks are probably the #1 cause of idle issues,so make sure you dont have any.
Its also possible, something as easy as a base idle reset could solve the issue.A dirty/defective iac valve,tps or stuck open purge valve are other known causes for idle problems.
http://sbftech.com/index.php/topic,2471.0.html
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Mylittlepony95

So I was driving it again today. It gets even worse as the temperature rises. The idle jumps back and forth and when it rises the car wants to jolt forward standing on the brakes, and when it bogs down it wants to die. It actually died on me in 5 O clock traffic on the highway. Quite embarrasing... and nerve racking having people take off and swerving around you pissed because they are ready to get home. I've checked over and over and over again for vacuum leaks because thats what I thought it was myself. If I havent found it at this rate, I'd need a new intake. I've triple checked for vacuum leaks. I did the IAC base reset procedure two times before, and not quite sure I was doing it right. It never made any kind of difference at all. Heres another thing. I never changed the injectors on this car. Everything else is new except those. They dont even have the caps that go over the needles on them. I plan on getting some 24ib injectors just to have new injectors and just to be safe because the engine builder rated it for 350hp. I feel like they could be the problem but at the same time, unlikely. If it is vacuum leak. I have no clue what to do about it anymore. I've checked all my voltages for my sensors and their readings on my moates quarterhorse and laptop. They all seem to read and work properly. The ranges seem to be good. So I guess my plan of action is to try injectors because they are practically needed. Just to rule it out (I know what a parts changer, not a real mechanic am i right?) then go from there. Idk I'm running out of ideas.

Buck Sergeant

Mylittlepony, all the responses are correct. Looking for a vacuum leak is definitely the first thing to do. Wbrocker's injector chart is on the money at 100% duty cycle. Here is a chart at 85% duty cycle. Also, be sure your fuel pump can meet your injector flow rate. Here it is.
Inj Flow Rate (@ 40 psid) Naturally Aspirated hp (@ 0.50) Forced-Induction hp (@ 0.65)
19 lb/hr 258 hp @ 85% Duty Cycle 199 hp @ 85% Duty Cycle
24 lb/hr 326 hp @ 85% Duty Cycle 251 hp @ 85% Duty Cycle
30 lb/hr 408 hp @ 85% Duty Cycle 314 hp @ 85% Duty Cycle
32 lb/hr 435 hp @ 85% Duty Cycle 335 hp @ 85% Duty Cycle
34 lb/hr 462 hp @ 85% Duty Cycle 356 hp @ 85% Duty Cycle
36 lb/hr 490 hp @ 85% Duty Cycle 377 hp @ 85% Duty Cycle
38 lb/hr 516 hp @ 85% Duty Cycle 398 hp @ 85% Duty Cycle
39 lb/hr 530 hp @ 85% Duty Cycle 408 hp @ 85% Duty Cycle
42 lb/hr 571 hp @ 85% Duty Cycle 439 hp @ 85% Duty Cycle
44 lb/hr 598 hp @ 85% Duty Cycle 460 hp @ 85% Duty Cycle
47 lb/hr 639 hp @ 85% Duty Cycle 492 hp @ 85% Duty Cycle
60 lb/hr 816 hp @ 85% Duty Cycle 628 hp @ 85% Duty Cycle
72 lb/hr 979 hp @ 85% Duty Cycle 753 hp @ 85% Duty Cycle
80 lb/hr 1088 hp @ 85% Duty Cycle 837 hp @ 85% Duty Cycle
98 lb/hr 1333 hp @ 85% Duty Cycle 1025 hp @ 85% Duty Cycle
NOTE: the first set of HP rating naturally aspired, is on the left. The second set of HP rating, forced induction, is on the right.

Buck Sergeant

littlepony, here is something else to take into consideration. Great electric fuel pump chart. As with the injector chart, give yourself a 10% plus wiggle factor. I install the 190L/hr pump on my 308 and 331 stroker motors.

Safe “Horsepower Capacity” @ 40psi with 12 V assuming 0.5 lb/hp-hr BSFC
60 L/hr pump = 95 lb/hr X 0.90 = 86 lb/hr, safe for up to 170 naturally aspirated flywheel hp
88 L/hr pump = 140 lb/hr X 0.90 = 126 lb/hr, safe for up to 250 naturally aspirated flywheel hp
110 L/hr pump = 175 lb/hr X 0.90 = 157 lb/hr, safe for up to 310 naturally aspirated flywheel hp
155 L/hr pump = 246 lb/hr X 0.90 = 221 lb/hr, safe for up to 440 naturally aspirated flywheel hp
190 L/hr pump = 302 lb/hr X 0.90 = 271 lb/hr, safe for up to 540 naturally aspirated flywheel hp
255 L/hr pump = 405 lb/hr X 0.90 = 364 lb/hr, safe for up to 720 naturally aspirated flywheel hp

Mylittlepony95

Mylittlepony95

Alright, I think I have a plan of action. I'm gonna have the upper intake milled. Change the gaskets on it. Check all the hoses and make sure they are not cracked and make sure the hose clamps are tight. Then while the intake is off I'm gonna put new injectors on. Put it all back together and see how she runs. I'll update in a couple weeks after I get it done. Thanks guys.

Buck Sergeant

littlepony, sounds like a plan to me. Be very careful about milling the upper intake. Remember, if you are milling the "upper" manifold, don't take off to much so as to change the angle so it won't seat at the correct angle to the "lower" manifold. Just do a light surface clean up. Also, you have a nicely modified engine there. I would suggest you install 24 lb/hr injectors and set your fuel regulator at 40 psi. After you get everything assembled, you can start thinking about getting your ride on a dyno and having it programed. Please get back with results.