ill4na8na2

Hello all. I'm having a problem with what sometimes registers as a multiple cylinder misfire codes or sometimes just a number one cylinder misfire code. I've searched multiple sites as well as this forum and couldnt find anything on my issue directly. If im wrong in saying any guidance to the right thread is appreciated.

I have a 2001 4.3 vortec lt blazer. It has 94k miles on it. i bought it knowing it had some issues. When i originally bought it it was throwing a multiple cylinder misfire but the check engine light was on all the time. the vehicle only ran rough at idle once given gas it ran fine. So i first change the spark plugs wires and rotor and cap. while this didnt fix the problem persay i then only had a number 1 cylinder misfire code no more multiple code. so i concluded after removing the upper intake that my fuel regulator was leaking. Since then here is a list of everything i have done:

-new plugs wires rotor & cap as stated above
-new intake gaskets-mainly i changed these not because it was necessary but because i noticed it was leaking a little on the outside of the engine block
-new spider injectors-and i bought the ac delco newer ones which i believe would mean i converted it but i could be wrong but thier new lol
-all new gaskets on the upper intake distributor & throttle body
-retimed the distributor back to tdc
-new drive belt

I mainly listed all of that so that hopefully itll help with diagnosing my problem. So anyways i finally get it all back together last night. Started it up ran at a high idle of 2000 rpms. ironically no codes thrown even at that idle. I then realized i had a vacuum leak which i found. plug the vacuum in and bam heres my multiple cylinder misfire code. After i plugged in the vacuum is when the code started showing again. and at that time my idle rpms were around 600. the odd part about it is it comes on sometimes blinking sometimes steady then goes off periodically. Then after the car warmed up it seemed to stop till i ran it down the road then it reappeard as a #1 cylinder misfire code again. So i went from before having a steady code to now a when it wants to code and it cant make up its mind if its multiple or one lol. Im hoping someone can steer me in the right direction.

The other question i have is could it have anything to do with the red ground wire, well guess its a ground wire, thats on the right side of the airbox on the drivers side front. After i let the car warm up i noticed that that ground is not connected to anything, i'm assuming the previous owner disconnected it at some point but i cant seem to find anything telling me what exactly it powers.

cleveland63b

have you done a compression or cylinder leakage test?

ill4na8na2

NO i havent ran a compression test yet thats my next step. First though i was messing with a few things last night and noticed that upon startup it runs fine idles around 900 motor runs good. As my blazer warms up the idle rpms drop slightly. then when the motor warms up to the hash mark in between 100 and 260 for the coolant temp my rpms drop at idle to 600 and thats when the code comes on. again sometimes it reads multiple sometimes it reads #1 cylinder. I was going to first remove the egr and clean it it juss seems odd to me where when i first bought it before i replaced everything it idle rough and at 600 at start up no matter what. now it seems to only do it as the engine warms. my scanner says the egr is reading -6.5 psi is that good or bad? i cant seem to find specs. Also is thier any other readings i can judge by using my code scanner? just trying to cover the basics before i go into compression mainly because the motor runs good other than after it warms up at idle.