I have a 1990 4runner with the 3VZE V-6, 273,XXX miles on the engine. Timing belt, waterpump, pulleys and camshaft seals @ 250,000 miles.
Here is the problem, it is running rough (skipping).
I put new plugs in it yesterday and that did not help. While running I pulled the wires off at the distributor and pulling the 1,2,4 and 5 plug wires made it run rougher; pulling the 3 and 6 plug wires did not make a difference.
I am going to try new plug wires next followed by checking the compression.. although I did the wires at 240,000 miles.
The engine also periodically starts hard.
The engine is not smoking.
The oil pressure is good.
No gasoline in the oil.
When the engine is rev'ed it seems to run smooth, but it does seem to be lacking power.
I have read the theads about the burnt exhaust valves and the bad injectors.
Any thoughts to point me in the right direction and keep me from feeling too much pain at the garage?
Thank you.
-Jeff

 

Do a compression test , that will tell you alot .

 

As for doing a compression test what are the numbers that I am looking for?
I am guessing that the compression numbers vary a bit with engine wear?
... and what would low compression in jugs 3 and 6 point to?
... and what would normal compression in all 6 jugs point to?

 

Try checking the 3 and 6 wires, you might have them backwards. When you pull a wire off the result should be the same for all the wires, a rougher idle.

 

http://personal.utulsa.edu/~nathan-b...fsm/index.html

With that many miles, I would be more prone to look for something "wear" related. I know Seafoam smooths mine out quite a bit. (Search on Seafoam - huge thread).

 

prolly got a burnt valve.i'm going thru the same right now with 303,000.soon as it dries up some here & can get room in the garage she's goin under the wrench

 

.... also, for what it is worth, the mpg is unchanged by this rough idle- missing situation. Going to try the seafoam... can't hurt.....I suppose.....