Ok, My wife has a 2001 Blazer, 2WD, 4.3L CSEFI. It will start fine, idle fine, drives fine when the throttle is 1/4 open or less. When you open the throttle over 1/4 it absolutely falls on it's face. If you back out of the throttle, it will begin to accelerate and sometimes if you stay in the throttle the engine will struggle to 3000 RPM and then pull very hard to 5000.

I have checked the fuel pressure (over 50 psi all the time), replaced the coil, and ignition module. Checked the TPS with Autotap and it appears to be reading the TPS fine.

It has set a misfire code (don't remember which one), P0128 (which I can not find), 02 Heater circuit code, and a code for the evap canister.

Yesterday it was running fine.

 

Evan, if you could give us the other codes that it's throwing, it might help out. Here is a .pdf, go to page 4 and it gives you more info on the PO128 code.

 

Checked the vacuum this morning. Put my gauge on the port that connects to the AIR pump behind the front bumper. SES went away! Vacuum was around 17 and steady. Noticed that the vacuum line going to the AIR pump looked a little dry rotted.

Replaced the 4 ft length of vacuum hose that leads to the AIR pump and the little foot and a half that goes from the vacuum switch to the diaphram at the AIR pump. This appears to have cleared everything up.

Drove theBlazer down the interstate, through town, filled up, restarted fine, drove up a couple of hills, and it runs like a top now.

Is it possible that a small vacuum leak or the AIR pump diaphragm not opening could cause all of this?

Thank you for the response, butI cleared the codes out to see what would come up again. Guess that I should have written them down.

 

Glad it's running good now. Keep an eye out for the codes coming back again and let us know.

 

It's back...

This time it is showing codes P0452 and P0300.

I don't think that I mentioned before that it is popping throught the exahust occasionally; When it has trouble getting up and going and I open the throttle.

I wonder if the FPR could be leaking, sending raw gas down the intake and causing the random misfire?

 

P0452 == Evaporative Emission Control System Pressure Sensor Low Input
P0300 == Random/Multiple Misfires

On the misfire code, I would have a read through this thread:
The dreaded PO300 CAUTION LONG POST AND GETTIN LONGER
Its a long thread, but covers the gambit on the P0300 code.

P0452 Explained

Hope this helps...

 

It just got worse...

Today it runs perfectly. No codes, no hesitation, popping, spitting, none of it! The part that worries me, is that I did nothing! My wife did not even drive it today, ARGH!

I'm beginning to wonder if the PCM could be bad. The first day that I noticed this was Saturday (a very nice sunny day), then Sunday when I "fixed it" the first time it was cool (50) and overcast, Monday nice and sunny and running badly, today cool (55) and rainy. I wonder if there is some connection?

 

It sounds like a possible pcm issue but that is a wild guess!!!

 

Two more cool days, two more days of running well.

At least it will be warm when I have to work on it again.

 

When you replaced the ICM, did it come with new thermal paste? The heat thing has me wanting to point to the ICM again... We recently had a member that went through 3 aftermarket ones in less than a month. Final solution was an AC Delco ICM and his problem went away.