Had to leave the truck at the shop today...they checked all fuel rails, fuel tank, throttle body, etc. They found no gas leaks...since it was almost 7pm, they told me that it is almost certain that the leak is at the fpr and that they'll check this today in the morning and change the o-ring if necessary, then they'll do the high pressure injector cleanup...

 

And your positive you don't have a vacuum leak?

 

I sprayed carb cleaner to all the vacuum lines with the truck at idle and it did not bog down or stalled even a bit...

 

Towel thrown...!
Here's the final diagnostic: Car is in OK condition...
This cannot be ok...they say that s-10's are shakers but, THAT MUCH?

They checked all vacuum lines, vacuum ball, vacuum tee, egr valve, throttle body, maf sensor, iac valve, map sensor, fpr, all fuel rails, fuel pressure, fp leak down test, checked for codes, checked all injectors and they are clean (maybe 'cause I pour one bottle of injector cleaner per month) , fuel filter, k&n fipk, air temp. sensor, pcv, motor mounts, checked tranny fluid, they even did a compression test!!! etc.
They found NOTHING!!!???
The only thing left to do is to hook the car to some machine that tests the amount of air/fuel mixture the car is doing...they will do this next week since their machine was out for maintenance...don't think this should be the problem because it is not smoking black or anything like that...
Yesterday I poured TWO bottles of Prestone SUV injector cleaner to see if helps out...

I love my truck because it is comfortable, has a smooth ride and it has power...I decided 1 year and 1/2 ago to buy it over the following vehicles: Toyota 4 Runner, Mitsubishi Montero Sport, Ford Explorer, Isuzu Rodeo...
The one I wanted the most was the Ford Explorer and the day I was about to buy a 00 model (with the dough in my pockets), I went to just check a couple of Blazers...I immediately was amazed how much smoother than the Explorer it was...I decided for the Blazer and cannot think that these cars shake so much!
I have thought about selling it due to this issue...but I love the truck!

 

Will spend the last $500 trying to remedy this issue...
Will buy the following:
-new fuel pump
-both knock sensors
-all 02 sensors
-new MSD spark plug wires

 

MSD is a waste of money. Just buy the Belden Premium wires from Napa. Lifetime warranty and damn good wires.

I don't think that the fuel pump has ANYTHING to do with this issue. Typically, a fuel pump works or it doesn't. They really don't have an in between.

O2 sensors possibly could, but unlikely. A bad O2 sensor (bad enough to screw with the idle quality) would be horrible under load (accelerating) and would definitely throw a code.

I guess the knock sensors could possibly be a problem, but a scan of the timing advance and knock sensor active count would verify if you are getting false knock, but again, this would magnify as load and rpm increased.

Have they checked out the harmonic balancer on the front of the crankshaft? Also, I am trying to think of a way to verify that the balance shaft is turning (driven by a gear off the cam shaft). Both of these can have an effect on your idle quality. Also, a cracked distributor housing can throw off your timing, but it should be apparent at higher rpms as well.

 

I would have to disagree on what you said about MSD...when I changed the stock coil to the MSD Blaster coil, the truck woke up...maybe the stock coil was going bad or something...but the truck was smoother when accelerating, hesitated a tad more with the stock coil...took out the msd and put back the stock coil and immediately felt the difference is the engine sound...don't think that I gained some hp but it is smoother and I am getting approx 1mpg more!

I am planning to buy an MSD 6A ignition and MSD plug wires because I have seen the results in some of my friends cars...you won't get more hp but you do get more mpg and acceleration is smoother, like it will not need more gas to get to high rpm's...

Regarding your question about the harmonic balancer...looks like they did not check that...
About the distributor housing...how can I check it?
About the 02 sensors and the knock sensors, you are right...in theory, it CANNOT harm the idle quality if not harming the overall rpm range...

Getting a bit desperate here...[:@]

 

My comment had to do with the wires. You aren't going to be pushing enough voltage, even with a blaster coil, to out 'flow' a set of factory wires. Now with a 7al box (don't know if you need to go that big), you might need a larger core wire. For that, I would buy a spool of MSD wire and cut to length, crip, and slap the boot on. Quality comes with practice, but you won't get a better wire for the price. Only down side is you have to buy a wire crimper and a spool of wire that you may use 10' of per job.

When it comes to wires, there are only 3 sources I would deal with. Belden, AC Delco, and MSD spool. I have seen many many quality issues with MSD premade wiresets. Things may have changed now, but a few years ago the wires were only warrantied for 6 months and would generally take a dump after 7.

 

Hey, I am thinking on the following noob stuff...

-Is it COMPLETELY necessary to use premium unleaded gas?
-How can I check if the spark plug wires are deffective? Maybe they are bad since I bought them new?
-I am running splitfire plugs...people have said many terrible stuff about them...rough idle, not enough spark, etc. maybe the gap is too small? but it is at .045!!! Maybe splitfires are not good in GM's??? They are about 1 year old only...

 

Are you running premium in your blazer? WHY??? 87 octane is all that is required.

You can check spark plug wires by misting water over them at night. If you get a light show, you've got a bad wire. Just take an old windex bottle (thoroughly rinsed out) and fill it up with tap water. Just mist it over the wires from the distributor to the plugs.

Pull a plug and have a look at it. If the center electrode looks worn down, replace them. If the gap measures loose, replace them. I can't exactly remember, but I could swear that I set mine at 0.055... I'll have to do some checking to find out what the correct gap is supposed to be. I might have my Bravada screwed up with my Bonneville.

I wouldn't put anything but a regular Double Platinum plug in the newer 4.3L. Just buy them from a reputable vendor (AC Delco, Champion, Bosch, etc.), but don't go for the +2 or +4 crap that's out there. It does absolutely NO better than the normal single electrode spark plug. Not to mention that you can't adjust the gap on those plugs at all. You need to check your gaps before installing your plugs. I pull all of my plugs about once a year on my Bravada and replace my plugs once a year on my Bonneville, but I'm only running regular copper plugs on the Bonneville due to their supperior performance with a blower.