Foxbody Tuning Questions

[JV106]

Just finished my rebuild and need any advice/input on getting it dialed in to get the most out of it. Right now the idle has been erratic. Over the past couple of weeks that I've had it running there's been times that it fired right up and idled strong, right now it cranks up but I have to nurse the throttle until it warms up.

I'm looking for any input from you guys that have already been through on a whole rebuild... Where you found hard to find vacuum leaks, where to check for bad grounds, fuel leaks, how you messed up the base idle reset, timing issues, valve lash adjustment mess ups. Anything that I can check to get it running perfect.

I've noticed that now, that kicking on the headlights seems to affect the idle, it comes down a little and struggles more than when they're not on.

I've had the car for 11 years, tore it down 5 years ago and it sat untouched in my garage then I did the following over the past 2 mos or as noted.

1990 Convertible GT with Tremec 3550

Here's the build:
-original 302, .40 over, fresh to me
-Anderson N41 cam, brand new
-Summit timing gear(s) noisy, brand new
-Edelbrock Performer intake ported, bought used as is
-GT40 Heads ported, bought used as is
-Crane 1.6 RR's Ped Mnt, brand new
-24# injectors, brand new
-Cobra MAF and Computer, installed by me 6 or 7 years ago
-Walbro 255 fuel pump, brand new
-All filters are brand new
-All vacuum lines are brand new
-All sensors are brand new
-Water pump, power steering pump, steering rack, and alternator are brand new (oriellys)
-Flex a-lite fan
-smog deleted with shorter belt
-Shorty headers, off road H, flows dumped
-Adj fuel pressure Reg (brand new) at 39 psi with vac unplugged from regulator and plugged at intake and at idle. I believe it stays at 39 psi with vac hooked back up and at idle
-EGR valve unplugged electrically and no vac hooked up
-timing at 12 degrees BTDC
-Brand new O2's, no wide band to check A/F
-Brand new IAC
-Charcoal cannister deleted
-Optima Red top, brand new
-TPS at 0.94 volts
-Stock dist and coil. New HEI module, plugs, and wires.

Sometimes while revving at idle it kind of hesitates before it winds up, sometimes while getting on it, it kind of hesitates.

Dash gauges lit up when I parked it 5 years ago but don't now. Dummy lights still work.

I did all of the work myself other than pistons/crank assembly. I'm not a mechanic, I did take my time and read a ton of tech articles on everything.

I spent a lot of money on this and want to make sure it's going to last and that I've got it done correctly. I know I'm kind of asking a long, vague question. Any advice is appreciated.

[blkpony98]

Needs dyno tune

[YALE]

Before a dyno tune, it needs to be gone over by someone with experience. PM Snatch Napkin. He has a great foxbody trouble shooting checklist. He can get you straightened out quick.

[Diabolic]

So it's a 93 Cobra computer or a 94-95 Cobra computer? DO you have the associated 24# injectors as well? If the idle is effected by the headlights I think your AFR is off a decent amount. The Batt voltage vs inj offset table adds fuel as the battery voltage drops in order to keep the injectors spraying enough fuel to keep the car running normal. When the lights come on the voltage drops and the table will add fuel to the tune. Perhaps you are running lean and this helps out the situation. You could also try unplugging the vacume to the fp reg. This will also richen the mix and perhaps validate the theory.

The fp should drop several psi with the vac line attached to the fp regulator. This is why Ford has high and low slopes in the strategy for the fuel injectors. It is interesting to note that the 94-95 Cobras used 24 for both the high and low slope. This basically kills the need for the inj breakpoint. Some people tune for injectors this way when there is not datasheet available.

[JV106]

93 cobra computer, aftermarket 24# injectors, since the build Ive ran both the factory 93 cobra injectors and then swapped for brand new aftermarket injectors. I did not notice any difference between the 2.

With the vacuum line unplugged at the reg and plug on the intake manifold it's at 39 psi. Vacuum hooked up it also runs at 39 psi. It holds 39 psi for nearly 24 hours before dropping while the car sits so I believe the fuel system is sealed up pretty well.