90thundergt

I have a 90 gt that I have modified, I'm pretty new to the game, so please bear with me. Mods: Edelbrock performer intake, BBK cold air induction, GT-40 turbo swirl aluminumn heads, 70mm throttlebody, F303 cam,under pulleys,Flowtech equal length shorty headers, 40 series Flowmasters w/turndowns</P>


My car ran fine for a couple of hours, then started to hesitate and backfire in the upper rpm ranges. It now does it when it gets above 3000. I have gotten all kind of advice from mechanics, but I need the help of mustang specialists.</P>


I've been told to go to higher octane fuel, replace my stock fuel pump, have my computer reset, and much more. I also need to know if I need to go to a bigger fuel pump and what lph would be recommended. All suggestions and recommendations will be greatly appreciated.</P>


<FONT color=red size=2>When ever I get my problem corrected,can anyone tell me what kind of horsepower can I expect?</FONT></P><edited><editID>90thundergt</editID><editDate>37951.7805902778</editDate></edited>

Black Horse

do you have larger injectors?</P>


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Black Horse

if this is a fuel problem, i'd so get 24lb injectors, make sure your maf sensor is calibrated for them, and get a 255 fuel pump...</P>


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90thundergt

I have stock injectors

Black Horse

well with your mods, i'd recommend the above, you really should get like alarger mass airflow sensor calibrated for 24lb inj., get some 24lb injectors, and a 255 fuel pump....your mods will definantly benefit from that, but i dont think that is causing your problem...sounds like a timing problem to me

95Stealth302

If you getting hesitation and backfire, its due to an air/fuel problem. Check 02 sensors, and emmisions system, along with Throttle position sensor.

jhogan2424

probably is timing. could be bad coil wire. it happened to me</P>


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horatio102

You don't need a new fuel pump. If the stock one is holding fine, just get an adjustible regulator. I'm pushing well over 300hp and the stock pump is working fine.

Quik

the tps and timing have to be in sync

SN95TT

did you break the cam in correctly? My friend's stepdad had this problem about 2 months ago on his '38 *****'s, he killed the cam. it ran fine, until he started hitting upper rpm ranges, then it started backfiring, and spitting and sputtering. you could have an air/fuel problem, but if it was running fine for a couple of hours......that makes me think that it could be a cam. check back with us on it.