92 jimmy 4.3 vortex high idle/stalls when shifting/egr ok/iac ok/more

this 92 4.3 vortex "w" was ok until it sat a while and started up running rough and has ever since except now it stalls when i put it in gear and sometimes when i come to a stop...unless i keep rpm up to like 1500...runs good down the road...new fuel filter and pressure are ok....egr was clean when i checked it except for the remnants of an old screen...at least i think it was a screen....i lost it when i cleaned up and didn't get to look at it real close....doesn't matter....anyway..i also cleaned the intake air control iac but it seemed pretty clean also..i'm willing to take the vortex cover off and inspect through the center hole where that round thing iswith the two torx screws....i'm beyond where i have ever been but i've seen the plenum off this thing before so i'm not afraid to go in there....have i missed something before i go ahead and do that???....what can i see through the hole to identify washing in the plenum???....do i or should i replace the so called nut kit and the regulator /cpi thing????....i can always change only what leaks when i get in there.....am i on the right track????

Get the fuel pressure guage on there again and check for fuel pressure leak down. When you shut the truck off, the pressure should stay there, it should leak down and lose pressure. If it is loosing its pressure, then you will most likley have to pull the upper plenum off and take a look and see if the lines, or spider(injector unit) is/are leaking.

Also, do you have any SES codes popping up?

thanks...i'm trying to get a hard hook up to the fuel pressure test valve but haven't located an adaptor yet....the ses came on briefly a couple times soon after starting but goes off shortly there after.....i'm on it but not just now...thanks for keeping an eye on me....fuel pressure draw down and idle vac....got it

i'm on it...thanks for keeping an eye on me.....fuel pressure and draw down ans idle vac report coming asap

i'm in two places at one time ....please help me at my post under gmc...jimmy...any help is greatly appreciated....we'll get it eventually..thanks

i did have codes #22 throttle position sensor which i changed ....and #15 coolant temperature sensor....this was the real culprit....i would like to know how this cps affects the fuel injection system...can you explain that to me a little....thanks...and thanks to automotive forum for all the help

I think you mean the CPI. The CPI "Central Port Fuel Injection" is the type of fuel delivery system your truck has. The spider unit has one central injector with little tubes/nozzles that go to each cylinder. These tubes carry fuel to each cylinder. There is one injector in the system and when it fires, all cylinders recieve fuel at the same time.

These units can and do leak, causing drivability problems, no start conditions, poor performance in general. The regulator can and does leak, which is located with the injector. Also, the fuel lines to and from the injector unit can becaome brittle and eventually leak to casuing problems too.

Hope this helps.

actually i meant cts ...coolant temperature sensor....i was curious as to what the failure of the sensor does to the fuel injection system....if there is any more to it than the failure causes it to run super rich...just curious....it raised holy heck with my starting and idling

The coolant temperature sensor is used by the truck's PCM to monitor the temperature of the engine. When the engine is cold, the PCM runs the truck richer until the engine begins to warm up to operating temperature. As its getting to operating temperature, the PCM adjusts fuel trim to proper ratios up to operating temperature. As the engine gets hotter, less gas is needed to run properly, kinda like a choke in the carburated days. Now if the sensor is not working quite properly but yet it is not setting a code off, it will run poorly, depending what the PCM is recieving from the sensor. If its reading that the engine is cool, yet the engine is up to operating temperature, then the PCM will be keeping the injector(s) open longer, makeing the air/fuel mixture rich, or basicly running rich. If the engine is sensed that it is operating hotter then it is, then the PCM will lean out the mixture, making the truck run lean, feel sluggish. The older OBDI systems had more trouble with this type of problem than does the newer OBDII systems, as the newer on board systems are much more powerful and have better capability to monitor faults.
Hope this gives you an idea.

my coolant sensor must have been sending a cold signal but i can't believe it would send a message to dump all the fuel in that it possibly could...of course i also had a code 22 throttle position sensor which i changed first...at first i could get it started by holding the gas pedal to the floor but in the end that didn't even work....so i'm also curious as to what message would be sent to the pcm when both of those sensors were inopperative at the same time....i probably was not getting that good of spark either....it all came together when i changed the cap and rotor and put in new ac plugs...stuff was growing in that cap....so i think that came into play somewhat....i'm not sure of the timing of the failures but over the course of a week it got progressively worse until i could not start it at all...