Rough Idle

[e-ranger]

Hey, I've got a '90 Ranger XLT with a 4.0L and an auto trans. Everything works great on the truck except the engine. The 4.0L has plenty of power still but it just started smoking pretty bad. It has the famous tick in the valve train and I was planning on replacing the lifters, rockers and rods with reconditioned parts.

Now, at idle, when cold, the engine used to have a miss that would go away once the engine warmed up. Now, however, it is smoking pretty bad at hard throttle and is missing all the time.

Could this be a problem with the valve stem seals? Also, does anyone know where I could get reasonably priced lifters, rods, rockers, and valves? I'm going to take the top end apart tonight to investigate and just wanted to put together a game plan.

Thanks in advance.

Erik

 

[MAKG]

If it's valve stem seals (or more likely valve guides), they leak when intake vacuum is highest. That is, coasting in gear with the throttle closed. You can get over 25 inches of vacuum that way.

YOUR problem -- IF it's oil -- is blow-by (worn piston rings).

But I strongly suspect it's not oil. Look at the spark plugs. Find out which ones are black and if they appear wet or dry. Dry black = carbon. It's a mixture problem. And you do NOT tear into the engine to deal with it (usually). It's a problem in regulation. Do you have a check engine light?

 

[Big Jim M]

E-R what ever you are thinking DON"T take it apart untill you KNOW what the problem is!! BLACK smoke is unburnt gasoline...grey or whitish smoke is oil.. Look at the sparks and see if they will tell you something..
Big Jim