my W 4.3 vortec blazer 4x4 4door had a serious issue
after reading about every post in the Blazer Forum, I am finally at the point where I thought i hadto write in to ask for some help
so many posts looked to be the solution, clean this, test that, backprob this, twist that. Yup a twist made the difference. My problem was that my MAP sensor was underpowered. 2.5 volts. I read howa few members said how the symptomsdisappeared because they replaced the MAP sensor. I was able to determine it was not faulty. However, because the voltage did not meet the reference output that meant between the MAP sensor and PCM. A good untwisting and re twisting of the PCM connecting wires re-established proper voltage. I did not start it up yet, had a beer to celebrate instead. Granny drive tomorrow to help reset the computer.

This leadsultimately to my question; Should I replace the engine wires to the pcm? Afterall, my truck is 10 years old. Can I get "new" wires?

NO CODES, the best two words for a blazer owner! update to follow

 

By WTO do you mean WOT = Wide Open Throttle? Just curious.

Also, if it seems to be activated by wet, you might want to check your secondary ignition components, mostly cap, rotor and wires. The cap & rotor can be visually inspected for arcing and carbon tracing, along with possible moisture, but the wires are easier to check in the dark with the engine running. Using a spray bottle, spray a little mist on the wires. If you see sparks, they're toast.

 

Thanks for the help, and you got me.darn acronyms. what i meant was that if you try to pass, or otherwise kick it down
wet, but this is constant and the truck has been in my garage for a week
the cap and rotor and wires are somewhat new and i did mist them with some soapy/salty (a pinch) water, no problems there
i edited my earlier post

[:@]the problem is back the wire to the MAP is messed up

 

Can I change the wires from the MAP to the PCM? or do is it necessary to change a bunch at once?

 

Itested various sensors (tps, iac, map etc) and they are under powered, less than 2.5 volts
I had it up to the 5 volts, but after about 15 minutes all the sensors were under powered again

suggestions?

 

What is the battery voltage doing through all of this? How about the voltage at the... Well, lets start by asking what year it is you are driving...

 

Thanks for the reply.
My blazer is a 1998.
I am not sure what you meant by asking about the battery
it is fairly new, turns the truck over with ease, gets used up a lot when i do the testing ie. key on (engine off)
i recently cleaned all cables and retightened them
Does the PCM have a ground? if so where might it be

 

hello,
i answered your Q. any suggestions?

I just tested the grey wire coming from the MAP with an OHM (sp?) meter and thist told me this wire is a problem. I looked this up in my Haynes book and it makes me ask a question
Does this one GREY wire go to more than one sensor, ie. EGR? TPS?

I need to know this as I was going toreplace the grey wire from the MAP to the PCM

thanks

 

Lets get back to what is actually happening here. What is the engine doing? What are you experiencing? You have never described the true problem, only that the MAP sensor is receiving (I think you mean receiving) too low of voltage.

And actually, not having codes is worse than having them as you have no idea where to start looking for a problem...

 

it is starting fine, every time, idles ok
however, it cuts out during normal driving, ie, from a stop, or to accelerate to pass
if you hold the gas down it will stall, if you feather the gas you can limp around and actually make highway speed, again can't pass or speed up

right now, my ohm meter says the grey wire from the MAP to the pcm says it needs to be replaced
does this make sense?
which spot in the pcm connector is the grey? i think it is next to the black, which is dead centre