misfiring

[crezz]

A couple of months ago I had a mechanic do a tune up on my truck. Only changed plugs however. Since then my check engine light has came on and is saying im misfiring on #7. I can only feel this between 50 and 60 mph on occasion. I took it back to the mechanic and he said everything is firing fine so he thinks its the fuel injector. thoughts on if this sounds right? any suggestions. thanks

 

[hemihustlin]

Swap the injector with a neighbouring cylinder. See if the misfire follows.

 

[Redtruck-VA]

It being a 03 I have to recommend removing the valve covers and inspect the valve springs. 03/04 are known to have a valve spring problem. If the valve happens to drop it can cause considerable damage. And of course #7 is the most difficult to inspect. Usually the mis-fire is on cylinder #6. Have you tried to cleared the code and see if it comes back? I would also check all the electrical plugs to ensure everything is tight. Also check the vacuum lines as they can be knocked loose when working on the engine.