Rough running, please help!

(94 s-10 blazer 4.3 vortec AT 4x4)

Ok awhile back my temp gauge was out, so i replaced both sensors and it still didnt work. so i bought an aux gauge and installed its sensor on the passenger side of the engine. it works fine, heres the thread about that.
http://www.automotiveforums.com/vbulletin/showthread.php?t=963198&highlight=exalteduser


I didnt drive the blazer much over the winter because it runs really rough for some reason now. At low rpms its worse, once i get it good and revved up it smoothes out. if in park its like that. if i try to drive it idles really rough and takes off really rough. i almost have to punch it and use the higher rpms to get anywhere. also getting terrible mileage in this condition.

It seems to run pretty rich as well. does this have something do do with these coolant sensors and not getting the correct signal to the computer? I mean i replaced the one above the water pump with a new one and i thought that one wasfor the computer. (details in the link above for that)

Also to note, i get no check engine lights for this, and the temp is normal on the aux gauge i installed 200-210 degrees roughly

How long since a tune-up? Check for any applicable trouble codes. Do you have the spider fuel system? Use a gage and check fuel pressure. Not only check for proper fuel pressure, check if the pressure drops like a rock, with key turned off. Even if the lite isn't on, I always check for codes, just a habit.

It is the multiport injection. i had great fuel pressure since i changed the fuel pump last fall with a delphii. i have not done the leakdown because i do not own a gauge, had used the autozone one before. i jumped the pins and i show no codes which is very odd. just an endless loop of flash, flash flash (which is the default right?)

As far as the tune-up goes, not since ive owned it. i never got that far because its been problem after problem. owned it for 6 months and gotten maybe 1000 miles driven on the damn thing. Theres so many other issues with it, i really dont want to dump more money in it since its pretty much going to get traded in or sold, or given to a family member. i have way more in it than its worth already and i dont want to "throw parts" at it for nothing.

If it is flashing code12, I guess there aren't any other codes. My info shows you have the spider system either that or TBI. My next step is the fuel pressure issue.

If you have a digital multimeter you can do an inductive test on the plug wires, engine running. You don't penetrate the wire insulation or take it loose, just touch. It will work on some makes and models. Say if the reading on several plug wires is around .5 volts and you have a couple that show zero, I know where to start looking. It's hard to do testing without a few tools. You can't rule anything out.

moneys been tight, i just got around to messing with this. pressure drops to 10 psi within seconds of me getting out and around to the gauge.

so i just removed the plenum today, and there is gobs of fuel on the drivers side(like an inch deep towards firewall) and its pretty clear the "nut kit" is whats leaking. however there were a few drops in the passenger side also, maybe spray-over? or regulator issues.

is there any way to use rubber instead of those stupid plastic lines? 54.99 at autozone-ripoff

regulaator is 49.99
these a-holes sure know how to make a killing on 5 dollar parts

i've never had any problems with the spider, but yours is a bit older than mine. there have been several posts about bad regulators.

i do know that you shouldn't see that much of a pressure drop on the fuel. check the pressure before and after the fuel filter. Old Master can prob give you the exact specs on what you should be seeing and the propor way to test your system. on fuel pumps the general rule seems to be: expect failure from anything but an ac delco brand...

pressure is fine at the tank, the pump, sender, all hardware is new. i replaced that stuff and drove it for 2 weeks before the internal leak started.

With new nut kit installed, plenum still off. key on is 62 psi just while priming (hard to see the thing thru the dirty windshield roughly 60+)
once that stops its at 56.
after 3 minutes 51
after 5 mins 49
after 15 mins 40

this is using the cheap harbor freight gauge that states +-2 on it

observed no leaks anywhere.

Am I safe to start putting her back together?

only thing left to do is fix the connector to the spider. the last time someone was in there they broke it and tried to silicone it. practicly fell apart when i touched it

Considering the guage ;) fuel pressure and leakdown are ok. 1994 CMFI Spec is 55psi to 61psi with the engine off and the pump running and remain above 50psi for 3 to 5 minutes after the pump shuts off. Should be good to go. Make sure you have a good, clean, tight connection at the injector.

just my luck
after changing oil, and spark plugs,
the last spark plug i go to change, #4 i believe, was just spinning. it must have been broken off inside. it came out with the nut, the threads and grounding electrode stayed in. Sigh
time for the easy outs i guess.

Thanks for the help guys ill post back after i get it all done

The Beast lives!
got that extracted and all done.
and wow this thing has never ran this good in its short history.
much thanks guys for the tips, now to tackle the bad encoder motor.....lol