odd miss fire

[Fsg231]

ok so i have a 88 gt with SD

here are the mods when i got the car....

Bosh plugs
MSD wires, Cap
e303
aftermarket fuel pump.... ( but i can hear it when i drive, or at idel

mods i have added,
New Msd wires
New NGK ur45 plugs
HeadMan Shorties
Bbk offroad hpipe
14 degrees on timing...
glasspack resonators

now when i drive at crusin speeds and i was too sepped up im missing pretty bad.
But at idel its perfect.... also when i floor it pulls hard then weaker, the hard again...

what could be the problem

 

[Fsg231]

um...any thoughts, it started too happen after the new mods, i did them all at once....

 

[crutch]

sounds like you're getting some spark scatter. or you might be dropping an injector... I'd inspect the inside of the cap and the face of the rotor. Make sure you're not growing anything green and fuzzy on them. I'd also get yourself a good set of noid lights from autozone or Pep-boys and check all the injector plug in's. then I'd do a spray test on all eight injectors

 

[blueblazes]

your biggest problem is speed density, they cant adapt as well as maf cars can. By changing the exhaust you have changed the way the car breathes and this can have an effect on way it drives to.

 

[fiveohlxhatch]

Did you double check your firing order? I've seen odd problems like this develop from switching two leads by mistake. The HO engine has a different firing order than your standard 5.0L

1-3-7-2-6-5-4-8

 

[Mustang5L5]

your biggest problem is speed density, they cant adapt as well as maf cars can. By changing the exhaust you have changed the way the car breathes and this can have an effect on way it drives to.

His mods shouldn't do much though. My setup is Speed Density and i have far more mod than he does. It should still be reasonable with the E303.



What are the plugs gapped at? I personally wouldn't run those plugs, but i don't think it would make a dramatic difference. Stock OEM motorsport copper plugs are far superior than a lot of the gimmick plugs out there when it comes to N/A setups.

I'd run the check engine codes. Speed density cars don't have a CEL, so you need to guess when it's time to run the codes. Could be O2 related

 

[Fsg231]

His mods shouldn't do much though. My setup is Speed Density and i have far more mod than he does. It should still be reasonable with the E303.



What are the plugs gapped at? I personally wouldn't run those plugs, but i don't think it would make a dramatic difference. Stock OEM motorsport copper plugs are far superior than a lot of the gimmick plugs out there when it comes to N/A setups.

I'd run the check engine codes. Speed density cars don't have a CEL, so you need to guess when it's time to run the codes. Could be O2 related

im thinking its the Ing Mod. going bad.... but then again the car ran fine with the new plugs and wires, then i added the exhaust and headers, thats when stuff started too act funny....

well im converting it this weekend too MAF, so that should rule it out it it still happens, but i ordered a Accel Ing. Mod. just in case.

 

[Mustang5L5]

Run the codes before you convert. It may give you a better idea as to what to look for.


I did headers, off-road Hpipe and cat-back to my SD setup and it didn't change a thing as to how the car ran.