When the engine starts the O2 sensor volts should be around .5 volts or 500mv so the 450mv is correct now i don't know wither your next statement is 115mv of 1150 mv it makes a big difference, so get back with me and i will see what i can do for you.
the 1 volt at the O2 ( 1000mv ) is rich so the sensor is working it is telling the on-board computer that the exhust is rich, now lets find out why it rich.....ist things 1st lets make sure that we just dont have an engine problem, a miss fire could cause thes problem, so is it hittion on all cylinders? do you know how to do a cylinder balance test? that would be the place to start. get back with me if you need to know how to do the test. or if you know how then get back to me with the test resaults. and we will go from there.
when you un-hook the O2 sensor you are putting the truck in open loop when in open loop the fuel system is not a feed back system any more so it just runs on a pre-programed program that was instaled in the ECM at the factory. if all you have is the plug wires then use them hold the engine rpm at a stedy speed and start removing plug wies one at a time and make sure each cylinder dropes the same rpm or with in 5% of each other.
does it have a high performance prom? it might be the prom it would be rair the prom is the programable read only memory it is used for all the base lines on the ecm things like cold start up open loop operation base timming max timming advance...ect. have you checked the base timming? also have you check the valve timming? the engine is rich the block learn is slowing the injection pulse trying to lean the engine, and it is unable to either because there is to much fuel going in the engine, or the fuel is not being completly burned. make sure the engine is runing on all cylinders and is in time both valve and base timing ( base timing is with the computer in timming set mode ) get a fuel pressure test and lets see wear its at.
13 is good, try this unplug one injector and see if the block learn goes the other way. up not down that will tell us if its a dillevery problem or a cumbustion problem.
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O2 voltage starts at450 mv continues to climb to 1150mv as engine warms and goes into closed loop. the engine starts to run rich and check engine light comes on rick exhaust i disconnected o2 sensor and engine runs smoother
the truck runs ok hot or cold with o2 disconnected. for cylinder balance test i have no way of killing each cylinder other than removing one plug wire at a time .
did cylinder balance test number 5 no ignition found broken reluctor tooth replaced distributor .did compression test 155psi to 170 psi cranking vacumn test 5-5 1/2 in and steady.same problem. o2 crosscounts go to 250 then back to 0. integrator values start at 128 drops to 41 as engine warms up and goes to closed loop. could it be a bad prom?
fuel pressure 13 psi at idle prom is stock updated number according to dealer timing 0 degrees with inline connector disconnected does not seemed to haved jumper timing
disconnected iac set idle at2000 rpm disconnected left injector blocklearn started to climb to about95 o2 volts no change. disconnected right injector blocklearn to 120 intergratorr to 128 o2 volts still at 1120 mv customer doesn't want to go any further unhooked o2 lead and road test drove ok but in limp mode thanks for the help
all info received was accurate and quick response thank you
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