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Engine idles ruff,gets better while driving,although not always.I changed plugs-right bank [2,4,6,8]are black & sooty. left bank[1,3,5,7]are clean.I replaced Cap & Rotor,fuel filter,air filter.Fuel pressure is 56-58#.Book calls for 60-68#.Is that atiquit pressure ? What else should i check?.  

vortec??????      i would bet that you have a blown out fuel pressure regulator...

it is changeable.. but you have to pull the upper intake off to get to it...

when it blows out...  half the engine gets soaked with the fuel leaking out the vacuum port of the regulator..


here is a drawing of the pressure regulator ,    number 1 is the regulator..

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/08/f2/4a/large/0900c1528008f24a.gif

this is where it is on the intake manifold after you take off the upper and the fuel lines..

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/08/ee/8f/medium/0900c1528008ee8f.gif


here are the fuel lines...

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/08/f2/55/medium/0900c1528008f255.gif


the fuel pressure regulator is available from most parts stores... under 70 bucks..

you will also need an upper intake manifold gasket set..

probably an egr gasket ..

take a look at the lower intake manifold gaskets... see if they are seeping at the ends..   they are notorious for leaks do to them being plastic and too thin around the water passages...

you might want to plan on a complete intake gasket replacement at the same time...  with a new thermostat and coolant..

while you have it apart half the way....


here is the complete intake manifold set

http://contentinfo.autozone.com/znetcs/product-info/en/US/fpr/MS98000T/image/8/

and yes it comes with new valve cover gaskets...  you have to take the valve covers off to get the lower intake off...

you will probably a lot happier if you do the whole job if the intake gasket has not already be replaced before..  

I did rplace the fuel presure regulator. I stil have the same problem. Any more thoughts?  

is it still fouled out on one side?????


blocked exhaust on one side????

clogged fuel injectors...   loose ground wires...  loose connector at the injector...  pins bent over.. or terminals pushed back..???


got any codes ?????  it should have several....

write them down..   clear them....    see if any reset..