Thanks for the replies.

About 11 months ago I put a nice set of injectors on it.
They were the new style. No Poppets. ACDELCO 2173028
I have a few weeks before the warranty is up on these.
I believe you get 12 months. Got them from Rock Auto

It had been running great up to about a few weeks ago.
Never a problem or code.

I have not down the leak down test.

Thanks - Mark K

 

Checked the tech article section of this site and looked up what it should take to set a misfire code.

Nope - 450-5000 rpm is the RPM requirement for misfire detection. If you have over 10% fuel, your coolant sensor reads a reasonable value on startup, and there are no other codes set then there is absolutely no reason why the system should not detect a misfire that happens more than 5 sec after the engine is started. Having to manipulate the throttle to keep the engine running is definitely a misfire condition.

If you want to purse this angle of diagnosis, then please let me know. I will expect you to not attempt more than one strategy of diagnostics at a time.

 

I'll try anything within my power to get it straightened out.
Not trying to get out of line from here, I think I have a Coolant
Temperature Sensor that does not read correctly at startup.

I am surprised and don't know why I don't get a misfire code.

I have only gotten 2 in my lifetime with this truck.
It made the Engine Service Soon light start blinking.
One was from a bad injector and the other
was from a worn Spark Plug wire.

Thanks - Mark K

 

So induce a dead miss and display that misfire counter on your scanner. Do the misfire counts increase?

 

Not sure how to do what you are referring to as a dead miss?

 

inducing a dead miss means to create an intentional misfire. I went out in my gararge and pulled out my old '97 shop manuals and looked up the complaint for "Rough, Unstable, or Incorrect Idle, Stalling". let me know if you can see the attached image ok. This is for the sensor checks. There's 2 more pages which include Fuel System, Ignition System, Additional and Engine Mechanical. If the image is readable for you, I'll post the other two pages.

 

Easiest way is to pull a plug wire and ground that term to prevent spark jumping.

 

I'm posting the other two pages on the chance they are readable. Doing from my tablet. Maybe they can help with your diagnosis.

 

Thanks for the replies.

The images came through nice and clear
on my lap top. Easy to read.

I'll try the pull the spark plug to induce
a misfire. It's dark out here now and
I live in an apartment complex. I'll
give it a try on first light tomorrow morning.

Appreciate the guidance and help.

Thanks - Mark K

 

I would like to thank Lesmyer and Rockp2
for taking the time to read and listen to my
ramblings/problems and for their responses.

It was my IAC (Idle Air Control Valve) all along.
This was a brand new part DELPHI CV10011.

It did fine for the past 10 months.
It must of been an intermittent problem with it
because the vehicle would actually run OK at times.

I had changed this out this part as a preventive maintenance measure.
The old one had 225,000 miles on it (OEM with the Blazer).

I am happy I kept the old part. I put in the old IAC and Bingo.
Everything is back to normal. Short Term and Long Term Fuel Trim
are almost always around Zero. I did not think that the IAC could
screw things up so badly. Even the Oxygen sensors are oscillating properly again.
It must have been closing completely when it got down to a low idle at a stop.
I will be sending it back. It is still under warranty for another month.

I guess the moral of my story is not to be too much of a preventive
maintenance guy. I have to trust more in some of the old OEM parts.
Even if they are 20 years old with 300,000 miles on them. The salvage
yards just got a little more appealing to me for OEM original parts.
I really think the USA made better parts back then.

After inspecting the 2 IAC valves I got to say the OEM looks to be built
more like a Tank. Better metal on the outside. I can't say what's
going on in the inside. Anyway I hope this helped somebody besides myself.

I guess my last question would be without changing this part out how would
you ever know that the IAC was the bad part? Especially since it was intermittent.
Never ever got a Code concerning the IAC.

Thanks Again,

Mark K