Hey guys,

I'm a new member however I've referenced this forum a number of times for previous problems and found it to be incredibly helpful. Lately, the problem with my 2000 Blazer 4WD 4.3L has stumped me. Here's my best explanation...

In July/August my Service Engine Soon light would turn on and off, usually coming on when I accelerated on a highway on-ramp. Back then it would go off within a few days and unless I really got on the pedal. Near the same time I noticed that the truck would sputter when taking off after start-up. This sputter would last for 100-200 yards before the engine seemed to "come to life" and drive "normally." This sputtering after start-up has remained the same and no matter how hard you push the pedal, the first 100-200 yards are a series of jerks and sputters. I've noticed a lack of power at highway speeds as well, best termed as a hesitation.

After noticing the problem I gave it a tune-up and replaced plugs, wires, and cap. I also replaced the PCV as I had seen someone on here with nearly the same problems report some success with this method. No fix there. I also cleaned the MAF sensor and this had no effect. Lately I've noticed 2 things. A) If the truck starts up without the Service Engine Soon light illuminated, it's going to be a bad day... Usually this results in problem B) after start-up sputters are over, the truck accelerates to 55-65 mph without a problem. Then the fun begins... the engine "cuts out" and lacks power... still running but unable to sustain any speed/power. This results in me pulling over, shutting it off, waiting a minute and starting back up. Often times after shutting off and starting back up the truck sputters at the beginning but does not "cut out" at highway speeds. I have observed that a start-up without SES light needs two "cut outs" to get the SES to illuminate, consequently running without cutting out. I took it to a buddy of mine who told me he pulled two stored Lean Exhaust codes (he didn't give me #'s but I'm guessing Code 44).

I'd appreciate any input from those who might be able to guess what's happening here. Based on what I've read I'm thinking O2 sensors or clogged cat (although it's not rattling), or even possibly plenum/spider problems. Any advice/thoughts/input? Thanks in advance and sorry so long!

-Mike

 

Could be O2 sensors...
Why don't you go and have it scanned, copy the codes down and report back. That will give you a lot better idea of what could be causing it rather then us playing the guessing game.

 

Yeah, lets start with the codes that the PCM has stored. There are many places that will read the codes for free.

 

Alright, the following codes were stored

131- Bank 1 Sensor 1
101- Mass Air Flow I believe
131- Bank 1 Sensor 1 (again)

 

Good. Now you can head here: https://blazerforum.com/forum/diagnostic-trouble-codes-dtcs-49/ and search for those codes. Read up on them and find out what they mean and how to troubleshoot them.

 

P0101 - Mass Air Flow System Performance
P0131 - HO2S Circuit Low Voltage Bank 1 Sensor 1

 

I have all of the same same symptoms .I also have a 2000 blazer with a 4.3 .
I have the following P O CODES
131 o2 circuit low voltage (bank 1 sensor 1)
143 o2 circuit low voltage (bank 1 sensor 3 )
151 o2 circuit low voltage ( bank 2 sensor 1)
This is what i've done so far
cleaned all ground points
replaced fuel pump
replaced three o2 sensors ,I think that is all of them
at this point i was working on the assumption that it was the o2 sensors are not working ,but i think at this point i know the are working fine .
so what causes a low voltage circuit reading ?
low voltage just means lean fuel reading ,
this will cause loss of power at highway speeds .
almost like a faulty transmission where you have to keep the fuel peddle down to get the speed you need . While you rev out the motor without the speed gain .
low voltage or lean fuel ,is it a proper response to a problem else where ?
what causing the lean fuel ? E G R ?
I'm thinking it's the E G R valve ?
What do you think ?

 

With all three of those codes present, I would look at a wiring issue. Look through the diagnostic pages linked to above and look for similarities.

Have you connected a scan tool and monitored the output from those sensors?

 

Found my problem .
Clean the two sensors on the air snorkel
the small one you have to pull out of the side of the snorkel,
clean it with contact switch cleaner and a tooth pick !!
The air flow sensor or the maff needs to be cleaned using contact cleaner and q tips
not so much the honey comb but the crystals which look like little diodes .
careful ,use very light pressure .
keep it wet with cleaner
bend the q tip in a 90 degree at one end to get in front of the crystals (diodes)
clean until there is no black residue .
Make sure everything is complete dry
that's it
All and i mean all power loss is gone drives like new again
no more codes No sputter on take off plenty of power burns rubber !!
lots of passing power
good idle
good starts
Hope this helps you
I over complicated the problem
and spent way to much money on my blazer
,,, live and learn

 

Hi Swartlkk
I used a obd2 code reader to monitor the drive ,when i was trying to duplicate the fault codes.
the tool i used only reads the codes the vehicle sends . what tipped me off to the actual problem was using this forum and google to understand how one system can effect another system in a multiplex wiring scheme . apparently those two sensors on the snorkel can mess up your shift points in the transmission .
all because of improper fuel mixture ,the improper fuel mixture alone seem to effect the other sub systems with this vehicle .
sorry for the late response ,i working odd hours this week .
any way have a good day