My truck idles a little rough so i was going to see if the pcv valve needed to be replaced, my question is what is the plug on the left head for??? Is that another breather???

Thanks

 

Could the rought idle be the IAC???

 

Could be the IAC, but that is only one of several possible causes. Actually, there are other things I would look at first, all fuel related.

As for the PCV valve, the port on the other side of the engine should go to the air cleaner. The PCV valve will take the built up gaseous crap inside the engine and allow it to be burned off. In order to do that, fresh air has to be brought in from somewhere. That is the purpose of the other port on the drivers side (318 and 360).

 

I started this thread a while ago, since then, i have found out it is a misfire in cylinder 8 and it is fuel related, so i am prob. going to get a new injector.

 

Let's see.......places to start.

1. plug gap ( 5.9'S had an updated plug to smooth out the idle )
2. intake pan gasket leak ( USES OIL WHEN THIS GASKET GOES ALSO )
3. Rust in the injector inlets...the fuel lines rust inside and it winds up in the rail and injectors.
4. distributor sync out of spec
5. cylinder leak down.....(crappy valve seats that don't seal well)

An IAC would only cause an idle speed issue, but if it's idling too low it may seem rough.

Lazy O2 sensors can cause fuel trim to go out of whack.

What year and what engine do you have?

 

its a '99 5.9. I have replaced the sparkplugs and wires so far. Did not make it run any smoother. Brought it to a mechanic and he found out that it was a fuel problem in that cylinder, so he put injector cleaner in it and told me to run it through a tank of gas, i am down to a quarter so far, and it has not fixed the misfire.