I have a 95 v10 with about 132k miles. It has been runnung rough for a while now. When I pull the plug wires off of the coil pack for cylinders 2,4,6,8 and 10 the engine responds as it should. When I pull the wire off of cylinder 9 there is no difference in the engine. On cylinders 1,3,5 ansd 7 there is very little difference. with After reading a few other posts, I am thinking about the 02 sensor for the side of the engine with the odd number cylinders. Any other thoughts

 

I'm confused on how making a cylinder fail to fire by removing the plug wire will lead to diagnosing an issue with the o2 sensor. And when you say the engine "responds as it should" when you pull a wire do you mean it has a misfire then or does not run rough then?

When does it run rough, at idle or through the whole RPM range? Have you checked the condition of the spark plugs? When's the last time the engine has had a tune-up?

 

When you pull the plugs, check for spark (you will need to ground the plug on something though, as it normally grounds to the block when you thread it in)

 

i agree with titan and grox...check the plugs...if the condition of the plugs are ok, then check the plug gapping (space between ground and electrode)...hopefully you don't have a broken piston ring or anything like that

 

#9 cylinder shows no significant misfire when you pull the plug wire off of the coil pack. Cylinders 1,3,5 and 7 show very little additional misfire when pulling the wire off of the coil pack. Clyinders 2,4,6,8,and 10 show a significant misfire when the wire is removed fron the coil pack. I runs rough at idle and throughout the rpm range,

The plugs were changed last spring and the plug wires were changed last summer (2009). All the plugs are clean. I have also checked and rechecked the plug wires and fireing order to make sure they are correct.

 

You need two things: spark and fuel. The best way to check the spark is to actually see it as the coil (I think that you have 10 coils), wire, or plug could be causing a lack of spark, so just disconnect the fuel pump relay, pull the plug, hold the threads against the engine block (grounding), and have someone crank so that you can see if there is spark.

If you have spark, now you need fuel. This won't be as easy to check, but I would recommend disconnecting the coils (unfortunately you will have to disconnect all of them), pull the plug, crank it, and see if you can ignite any fuel in the cylinder with a splint or lighter. Or you could try pulling the fuel rail or whatever mechanism the V10 uses and cranking the engine to see if it is spraying.

If you have fuel and spark, then it is a timing issue, usually the firing order, but it sounds like you have double checked that a few times.

I can't imagine that it could be an 02 sensor issue.