Pulling the valve cover is a quick way to check your valve train, and may be worth your trouble. Or as lew52 suggests it could be your cam. Get some rocker arm oil plugs, start the engine with the cover off on your #6 side and see if they're moving. If not, then it's likely your cam or some other valve train related problem.

But from what you're describing, it sounds electrical to me. Especially the part about the idle jumping and the shifting. If your TPS is still good, then I'd begin checking other sensors- every sensor in the book.

Remember- the computer is constantly making adjustments for running conditions. If one or more of your sensors is bad, the computer is making adjustments for conditions that don't exist and therefore is causing the rough running.

And I probably asked you this once before, but have you pulled codes lately?

 

Ok, I have found a vacuum leak around the upper intake mating surface to the lower intake.

Where exactly was the leak?

Bad lower intake leak could cause a miss, a leak at #6 cylinder but would have to be pretty severe. I use a garden hose to check for vac leaks if one is suspected. Turn the hose on medium flow, start low working your way up watching for steam out of the tail pipe, the second you hit a vacuum leak with the water white steam will be apparent out the tail pipe (exhaust system must be in good shape)

I replaced the fuel injector with a new one I had in my box and it did nothing to stop the miss. I also swapped plug wires and plugs with no luck either. I don't know what to do now. I have no idea why I have a miss. I have checked the voltage on the injector connecter along with the two adjacent injectors and they are all the same. Any thoughts?

Ok the injector was not the problem, well based on the fact the used injector you tried, worked right and was not all gummed/plugged up from sitting? Doubtful yea but main reason I suggested swapping it for one right next to it, see if the miss follows that injector.
Swapped wires and plugs, good but did you pop the cap off and look to verify its fully intact? Nothing missing, no cracks etc etc.

Also today while I was sitting in the truck with it idling, the idle jumped up to about 1800 all of a sudden and when I started driving home it was shifting bad and sometimes jumping into second or third gear while I was going slow.

First part sounds like a IAC issue or a sudden vac leak.

Second sounds more like a VSS problem, your model year it should be in the top of the rear diff.
May also be a MLPS down on the side of the trans, not really the correct symptoms for it though.
Doubt has anything to do with the miss.

Your continued comments on the high idle leads one back to thinking a vacuum leak is in at least part the problem.

 

Ok, I pulled the valve cover and nothing looks wrong. I cranked the engine a few times and both valves on #6 cylinder are moving just as much as all the others. Now I am really lost. Nothing is making sense. I know I still have a vacume leak on the upper manifold so I will be taking it off again at some point, but this dead cylinder has really got me. Any thoughts?

 

Got me ?? Your sure you have comp & spark at the plug . Check your firing order & make sure none of the plug wires are touching each other , make sure nothing is arching , start it up at nite when its dark & see if you see anything . Not sure whats up with your manifold leak the gasket shouldn't go bad that fast , check the upper & lower with a good flat edge to make sure its not warped.... Lew

 

I just realized that what I have been calling number 6 cylinder is actually number 7. I thought they went 2, 4, 6, 8 on the driver side. Anyway it is missing at #7. Yes I have checked the fire at #7 a couple of times. I take the plug out, put the wire on it, ground it, and start the engine and it fires just fine. Also the compression is the same on 6, 7, and 8. Also I have #7 and #8 wires run separately. I have swapped out #7 and #8 plugs and wires and the miss is still at #7.

Is there anything else I can look for in the valve train before I put the valve cover back on?

 

Check the # 7 valve springs good , when the valves are all the way closed make sure there is no play , give a hard push down on the push rod end of the rocker , it should be tight , Its not unusual to have a valve problem like a burn't valve but that should show up with the comp test . Mabee someone has a new idea , were missing something here ???????

 

I'll check those things and then put it back together. I am not expecting to find anything because I just had the heads looked at by a machine shop a couple of thousand miles ago. They had new valves and new guides in one of them. I still think it is something electrical but I don't know what. Thanks for the help.

 

Just a thought , make sure the plug that goes to the injector is clean & tight & is getting a good conection...

 

I think it is because I can hear it start clicking (with a mechanics stethescope) when I plug it in and it stops when I un plug it. I am starting to put the valve cover back on now. I greatly appreciate all the help.

 

I have got everything back together now including new upper intake gasket so hopefully I have at least fixed the high idle. I will wait until tomorrow to start it so the rtv can set up. I believe I am going to start all over at the basics on diagnosing the dead cylinder. I have either overlooked something or it is possessed!

 

All right, I tried it out and still have the high idle and miss. I poured water all over the lower intake and the idle dropped and I heard a louder hissing noise and then white smoke out the exhaust. So I believe I have found my major vacume leak. Now it seems to be right at #7 cylinder also. Could that be the missing problem as well? Maybe it is running really lean and acting as a dead cylinder? Hopefully both of my problems are in this one leak. Unfortunately I have to take off everything I just put back on! Of course I am becoming a master of disassembling it. Do these things make sense? Thanks for all the help.

 

Thats the problem if its at the base of the intake were it meets the head on # 7 . I thought it was leaking at the upper & lower gasket ??? Let use know how it is after you replace the intake gasket ...Lew

 

Little water tells the tail fast don't it?!!

Yea it could be drawing in so much air there its just not getting the fuel with it, would have to be a very substantial leak though. But based on what you said here it sounds like you have one.

Pull the lower intake and reseal it and all your problems should disappear.

 

It was also leaking at the upper intake also. I used black rtv in the past and had the upper leak so the last time I put it together, I used some copper seal spray for all the gaskets and apparently it is not good for anything except head gaskets. It was extremely tacky and I thought it would work well, but it is not very thick. I don't remember putting anything on the lower intake gaskets because they had the blue stripe going around all the ports. Do I need to put something on there anyway?

 

I always use sealant on any type of intake gasket where a good seal against vac leak is a must regardless of what the gasket is like. If its a thick/er gasket I use a spray sealer like copper spray, if its thin with little to make up for uneven surfaces I use a thicker sealer like permatex form a gasket. I limit use of the silicone type sealers more for sealing against fluid type leaks like oil or gear oil where no real pressure or vacuum is involved.

I also use the permatex in the can with a brush, semi thick with a brush connected to the lid. Real sticky and never had a leak using it. Kinda a middle ground between the super thick form a gasket and the thin spay sealer. Works good where you want a sealer with good body to it but where uneven matting surfaces are not a big problem like in today's engines.