need some troubleshooting help...

I purchased a 1997 4x4 Ram from my neighbor. It has 111000 mile on the 360. The truck starts just fine and other than the slightly rough idle (which I
am told is a pretty normal occurence in this engine) runs great while sitting still and also has great accelleration and high speed (70+ mph) performance. The problem is that while the engine is spinning at about 1700-2200 RPM, a miss can be felt which makes the truck, well, "shimmy" as I run down the road. Not the shimmy you feel when a tire is out of balance or round but the shimmy you feel when the engine is running sub-optimal. I put new tires (265/75/16) on all four corners and had them balance them twice and show me the readings as they did it so that I could eliminate a problem with tire balance. I also notice that if I shift down while the shimmy is occuring, it abates quite significantly but does not entirely disappear. I took the truck up and had new dual exhaust put on (thrustmaster II) and while in the shop they hooked it up to the diagnostic computer. While there were no codes set, it was showing that the engine was running lean at those RPMs. So here is my plan and I want to see if it makes sense. I have already replaced the pcv valve, cap, rotor, plugs and wires. I have a K&N drop in that has been cleaned and re-oiled. carb cleaner has been used to clean the outside (and inside where possible) of the TBI.
Since it is running lean, either the computer is getting input that the mixture is plenty rich and cuts back on the fuel even though, in reality, the mixture is now off or The computer has no idea that it is lean and is putting the perfect mixture through the manifold and the leak is occuring where the computer cannot detect it and fix it.
My logics says I should:
First, start with the O2 sensor(s). Do I need to replace all three or is there rhyme or reason to which one to try first?
Second, I thooght about the fuel system itself. Is it possible that the computer is telling the injector to put in X amount of fuel into the cylinder but the injector is unable to deliver it in the amount of time specifed? Can injectors really be clean without removing them or is replacement the only true option?
Third, The intake manifold gasket. It was replaced by Chrysler when the truck had 36K on it for the vaccumm leak problem and I wonder if it could have happened again.
I am up for suggestions since the O2 sensors are about 45 bucks each and any of these option will eat into my precious "sit-in-my-chair-and-watch-nascar" time. :-)
Thanks in advance for any ideas,
-Jerry jerrynatlga(AT)gmail.com
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I have had three 360 powered vehicles:
A 74 Roadunner (best 360 ever by far) A 77 Power Wagon (Horrible in so many ways) A 84 or 85 Ramcharger (Cant remember what year, I sold it almost immediately back 10 years ago a week after I bought it for an insanely cheap price..
They ALL did this. From day one. I fixed the problem on the Roadrunner and Powerwagon by rejetting and/or a metering rod change. The Ramcharger was gone after I changed the manifold gaskets. The 74 had no problems with the intake gaskets, but the 77 took drastic measures (The most obnoxious smelling sealing stuff) smeared on them to solve it, after changing them several times, once by the dealer, once by a garage, and three times by me. Of course, if the heads would have been even remotely "straight" it would have helped a lot. The stock manifold was warped to match the heads, so it wasn't too bad, but it cracked and I wanted to go to a 4 barrel carb and so I bought an Edelbrock intake and it WAS straight, so not only didn't it seal well, the damn bolt holes had to be enlarged to put it on. Fine quality back in 77.
One thing, and I don't know how the later ones are set up, that made this problem much worse was that the vacuum advance in the 77 caused the distributor pickup to graze the pole piece at a certain point in it's travel. I found this out by putting it on a scope and it had a certain RPM point it started misfiring and we found out if the advance hose was disconnected, it didn't do it. I ended up buying a Direct Connection replacement distributor and having it recurved slightly (stock it pinged badly) and it helped a lot, but the cure was a little more fuel..
I passed on buying a Ram in 2000, I just couldn't buy another LA engine, so I bought a GMC instead. After it was wrecked, I bought a 2003 Hemi Ram. I sure don't miss the 318/360..
Good luck..
BDK
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I feel dumb when I read this forum.
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You are reading this news group which puts you head and shoulders above most other vehicle owners!
-Jerry
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EDTHEWARD wrote:

LOL
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That's good..I feel like a drooling idiot when I read it :)
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Gene wrote:

That feeling will pass. Take a deep breath, count to three.... ;^)
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I replaced the O2 sensors. There were actually only two, one upstream and one downstream. Downstream went on like a charm, upstream stripped the threads off the old sensor and had to drive all over town to find an 18mm tap to clean out the Cat converter hole! WHAT A PAIN!!!!! finally got it tapped out and 5 hours after starting, the second sensor is in. Now I am afraid to drive it since it will depress me if I just spent 130 bucks for two un-needed sensors...
-Jerry
P.S. I bought the gasket set for the manifold so I may be busy tomarrow too! :-)
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I resemble that remark. I changed all the parts you did, plugs, wires etc, before changing both sensors. Still did not solve my problem. Then bought a Davis CarChip and captured my data flow. I found that the fuel system in Bank one is running open loop. Oh well, the CarChip will continue to help in the future.
Old_Timer
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