Patski

Hello everyone.. I am new to this site... I am posting this question because this problem has been wrecking my brain. Usually I find an answer on google... but this time no luck.

Here is my problem.. my 1987 Mustang 5.0 runs perfect when I first start it and perfect when its warmed up... but once the temperature gauge comes off the bottom... it will misfire very bad until the temperature reaches normal, about half. As soon as it warms up, its like clicking a switch from horrible to perfect. It happens every time I start the car... no matter on weather, rain or shine.

The car has GT40 heads, a B303 Cam, and was converted to Mass Air from speed density.The problem started long after the engine work was done.Since the problem started, I have changed the Mass Air, all 8 injectors, had the EGRremoved and blocked off,and replaced the EEC temperature sensor... all with no change. I unplugged the air intake temperaute sensor mounted on the lower intake... and it acted the exact same.

I am seriously stumped... any recommendations out there???

Thanks

AdderMk2

with the sensor unplugged, and it acted the same.... means you have a bad sensor

67mustang302

Honestly, next time that happens find someone with a scanner that can check it for you before you spend money on stuff you don't need to

grabbem88

yep gotta go with mike here..mine was doing similiar things when mine was sd...having that unplugged is telling the car to go rich,and if i'm not mistaken the factory computer is pulling timing so when most likely are putting the car under load you create a backfire.alot of fuel to less timing equals backfire

loeryder21

my 86 does the same thing i just ordered new sensors. I'll let you know if it helps.