so i just rebuilt my engine bored it 30 over and put a very light cam in it. engine ran great on start up break in and for two very short test drives. engine is now missing under a load most of the time. sometimes it will miss with out load just raising rpms. also has noise sounds like coming from exhaust when it happens. anyone have a suggestion?

 

What engine do you have?

 

check the MAP sensor

 

i have the 4L fuel injected

 

Did you do the rebuild?is it possible the lifters are adjusted to tight,when you first start them up it takes a little time for hyd lifters to pump up and once they do they can cause the valves to hang open slightly cause this condition.

 

Did you mill the block and/or head mating surfaces? If so, and it was both, there could be an issue with the pushrods being too long now. JMO

 

thanks everybody for your sugestons.head was surfased but not block.valves are not ajustable. i have replaced map/mat censer. sugeston was made that the computer does not reconize the rv cam.also the knock censer could also cause the mis. help.ido not want to put in a stock cam.thanks. engine starts great-runs good untill it warms up.then the motor idles good but starts to miss as i rev it up .please help .

 

You said a heavy miss under the hood. Do you have one of these..............
under your hood???