hpi09

I just bought a 1992 LX 5.0 mustang 5-speed. I got the car cheap because the guy couldn't get it to run right. He put a 255 gph fuel pump, 24lbs injectors, new calibrated mass air flow, cold air intake, and exhaust. Now it doesn't want to idel and is jerkie under 2000rpm above that it runs great has great power and cruises fine as long as ur over 2000rpm. I think it needs a custom chip any help would be great. If it does need a chip who makes the best one? Thanks for any help.

mattdel

it doesn't need a chip. it needs a diagnosis. the injector upgrade wasn't a great idea considering that you posted no other mods, so i'm assuming the rest of the motor is stock. therefore bigger injectors are essentially flooding the system, which could result in the symptoms you are experiencing. over 2000rpm you would have sufficient airflow into the motor to properly combust the additional fuel.

just a guess.

hpi09

Thank you for ur help that makes alot of since. The motor is stock other than mods I posted. What size injectors should I use? I plan to run a 100 shot of NOS. Thanks again.

zebo87

yeah with that fuel pump and those injectors you are running rich. diagnosis is a must. you could also have a vacuum leak.

Tony71502

Stock injectors are all you need.

hpi09

Thank you for ur help. Do I have'd to change the mass air flow meter also? and do I need to change the fuel pump. Thanks for all ur help.

mattdel

the fuel pump makes no difference, the excess volume that it pumps out just returns to the tank anyway.
yes you will need to change the MAF.
#19 injectors with a stock MAF should be good.

hpi09

great thanks so much for ur help and quick responses.