Missfire code and constant mis

[stang 1989]

I have a missfire code and constant mis on my 99 xls ohv 4.0 i have changed all of the normal suspects plugs, wires, coil pack, fuel pump, filter, and injectors. Any help would be greatly appreciated.

 

[Doubt Incarnate]

does the missfire code point out a specific cylinder? did the old plugs look good? consume oil? maybe a vacuum leak, or if you have a really bad valve seal your motor could be sucking oil in and drowning a plug. real bad senario is cracked head or bad head gasket.

 

[stang 1989]

The code if #4 cylinder the plugs looked fine no oil on them just wore out. I have a guy that is going to check it for a vacum leak. The funny thing is sometimes it doesnt do it.

 

[Doubt Incarnate]

could be vaccum, sometimes temp affects the size of the leak, going from insignificant to annoying.

 

[stang 1989]

Thats wht i was thinking it is very annoying.

 

[Vinniety]

I had the same problem and i went ahead and changed alot of things until i read a post about upper and lower intake gaskets which are common issues with the OHV motors. 5k miles later truck still runs fine.

 

[stang 1989]

I have had the upper intake off and changed the gaskets in it when i changed the injectors ill try the lower and see if that cures it.

 

[rego]

I had the same problem. #4 not firing,very noticeable miss,new plugs and wires,and all injectors replaced. A hired a good mechanic to diagnose it and he ended up fixing it in the process. Turned out to be the MAF sensor. He had to do more than a spray cleaning. He used a cotton swab to get something like lint off. That's not normally done because of how fragile they are as I understand it.

 

[stang 1989]

I changed the gasket set and cleaned the mass air sensor now the egr is throwing a code gotta clean it now thanks for the help

 

[NHale623]

Before you go taking the EGR system apart, you might want to post the code you have. There are multiple components to that systems.