I have a 1991 Mustang just picked up about a month ago and I'm trying to get all the bugs worked out I have changed plugs cap and rotor, and set the timming at about 10. But the problem i have is that on acceleration the car will start to backfire at about 3500 rpm's it does in 1st and 2nd gear. If you could give me any suggestion that would be great.

 

is it a backfire or like a miss? has there been any mods done to it ?

 

There are no mods yet. And it could be a miss but it sound more like backfire to me.

 

When it backfires,is it out the inatke or the exhaust? Depending on the exhaust, sometimes its normal for it to backfire through the exhaust.
-P.

 

yes it come out the exhaust

 

May be running a little too lean. Iono.

Mine does it too a bit.

 

Timing.

I'd take it down a degree or two and see if it goes away. If it does then you are golden. If you still want the advance, I don't know what to tell you.

-Ivan

 

Get a Fuel pressure regulator to check your fuel pressure.

 

^^+1

I forgot to mention a AFPR, that would make a hella difference.

Good luck to you,
Ivan

 

Whats the most accurate way to check the pressure? Through the schrader valve? With the car running or off?