My truck is having about the same issues...I believe we share the same engine...I think it's the distributor on mine from what I've read. Here's my thread lol...

https://blazerforum.com/forum/2nd-generation-s-series-1995-2005-tech-41/random-p0172-misfire-below-700-rpm-37143/

 

Just to weigh in on the temp sensors, yes the upper one is for emissions and the one on the passenger side is for the gauge. Been down that road resurrecting mine from the dead. The one on the side is a single wire while the ipper one has two wires and goes to the PCM (or ECU - whatever). They are definateky not the same part. I only paid like less than $20.00 for mine. By the way you can change bthe bulbs in a digital cluster. Your owner's manual tells you which ones they are. To get the thing out I would recommend you go to this website.
http://home.comcast.net/~digital_das...formation.html.
I bought one of his clusters because there was a bunch of stuff wrong with mine I couldn't fix. These are the removal/installation instructions and they give you some tips the factoru manual doesn't even cover. When you ground the temp sensor it should peg the gauge but the way you're supposed to check it is with a decade resistance box. Cheapeat one I found was about $40.00 and didn't want to spend it on something I might not use again. I just took a chance and replaced my sensor since I had a rebuilt cluster. Works like a champ now. I'll second the "be quick" tip. I still had a big drain pan full of coolant when I was done.

 

thanks guys for all the suggestions and help. I'm gonna take the cluster out and change the bulbs and may pull out the distributor and look at the gear on it(i was actually gonna put a timing light on it but haven't got around to it yet. I just hate to see it go to the junk b/c its in pretty decent shape. although it is another example of a poorly taken car of vehicle. when mom bought it, it didn't run.

thanks for the help and i'm still open for suggestions.


i'll post the results when i figure it out...

 

Brother you haven't seen "poorly taken care of" until you've seen mine. It didn't run either and I was trying to do the nephew a favor when I bought it off him. Cheap. Boy did he get in my knickers. I will say that I haven't been bored. Actually learned some stuff too. You name it, there was something wrong with it. Still finishing it up but it's legal to drive at least.

 

have you guys checked your EGR valve to see if its clogged or stuck open? how about checking to see if your cat is clogged up?

 

I put a new EGR in and cleaned it out 3 times when it clogged...this last time it wasn't clogged and made no difference.

 

mines got a new egr on it. i'm gonna cut the cat off also. Yeah this thing started out cheap its actually my moms truck but i get to do the work to it yippie! It has more probs than she was told thats for sure.

 

have you done a fuel pressure test to see if is looses pressure? there is a port on the back of the CPI intake where you can hook up the guage. you should check the pressure

 

no i haven't i don't have a fuel pressure test gauge. I'll have to go to the parts store and get one. What should the pressure be about 60 psi?

 

Yup, key on - 60, it will bleed down to about 40, then when its running it should sit at almost 60 again... Theres a little valve it threads onto to the right of the distributor cap (drivers side of it)

I got a guage for about 50 bucks, it came with ford and import adapters too.