Last week I purchased a 1996 SE 3.8 engine with automatic transmission, 95k miles. Found out pretty quickly that it was using coolant. Had the dreaded lower intake manifold problem. I was quoted $700 by a local shop to fix..so I put the parts in mysellf. I used the Dorman kit that includes a new Black plastic manifold, stovepipe and upper gasket, I used an FelPro gasket set on the lower..maybe not the best choices?
Found out after the fact that I did not position the clear plastic tube into the PVC valve correctly. ( I have another post on that)

In addition to the gaskets,
I flushed the system and refilled prestone. and Installed a new radiator cap. I ran a bottle of techtron fuel injector cleaner through the gas tank, I changed the oil & filter, new air filter. new transmission filter and fluid, new fuel filter, spark plug and wires. and installed a new downstream oxygen sensor. I suppose I should do the 180 degree thermostat change out that I read about here?

Any way now that I have all this maintenance done I am having a couple of problems that I din't see before I did all this. The check engine light has come on a couple of times with code 171 (lean fuel mix ) and I just got a 304 (misfire on plug 4)

I'm thinking that the last time a saw a 171 was on my wife'* Grand Caravan and replacing the fuel pump was the fix. I suppose the misfire on 4 could be caused by lean mix on ther rear bank..since 4 is on the rear. Any ideas what I can try? The fuel filter looked like it had never been changed..(it was an AC Delco branded filter maybe original equip, same for the transmission fluid/filter looked like it had never been serviced.
Did I loosen up a bunch of crap in the gas tank...Is there anything I can try to resolve this short of replacing the fuel pump? The engine seems to run pretty good.

A third problem that has just shown up is with the Traction Control. The buttone next to the shfter... is shutting itself off. When I try to turn it back on it doesn't turn on(button doesn't light and the TRACTION CONTROL IS OFF Message on the dashboard doesn't turn off) A minute or 2 later I press the button and maybe it takes..and the button lights and the message goes off on the console. Any ideas?

Spit

Sounds like you have some complications with the recent UIM replacement. My suggestions would be to clear the codes and see if they come back.

P0171 has been caused by corrosion with the battery cables and poor connections. Look under the rubber boots at the battery as well. It has also been mentioned by another memeber recetly to have been an Evap purge valve being bad and causing a vacuum leak (although typically a leak does not set the code). You should also check to ensure no plug wires are touching the O2 wiring, that can cause a bit of havoc.

You can cause this with a vacuum leak if you leave out an 0-ring on your PCV when you swap intakes, also. With the car idling, pull the oil fill cap. Is it sucking air?

I found my problem. I had disconnected the EGR tube at the EGR Vale itself in order to remove it from the manifold. I my haste I only finger tightened it at the EGR valve. After reviewing some posts on this site (WHAT A GREAT SITE THIS IS !!!!) I took a look at the EGR and right away I could see an air gap...tightened up and no more codes...running much smoother.

Spit