Hi Guys,

I'm getting my 2000 blazer, v6 4.3L ready for sale. I have a rough running idle and a near stall at initial acceleration. Reading with my primitive reader I have P0171 and P0174. So far, I've cleaned the MAF sensor. The first problem here was that screen at the from of the sensor was missing! I don't know how, but you could see the resistors on the wires. Either way I cleaned them with SensorClean and away I went. At that point the PO174 disappeared for the night, but is now back.

I checked for air leaks in the conduit to the throttle body assembly from the air filter, and visually it looks good. I crawled under and visually inspected the exhaust piping from both manifolds and they are fine. I inspected the exhaust all the way to the catalytic converter and past it and it's fine.

What I did find was an exhaust leak just past the muffler in the tail pipe, there are two quarter size holes from rusting right where the tail pipe meets the muffler.

My questions are,

1. Should the MAF sensor assembly have that screen on the air filter side? This seems like it could cause me problems with out it.

2. Should I just go and get and replace the bank1 bank2 o2 sensors? They are 96$ each at NAPA. Also they are rusted in as hell, it won't be easy. Also I understand there is no way to clean and test them, it's a whole replacement.

3. Should I first fix the exhaust leak past the muffler (using tin tape), and see if that changes things. From my understanding though, the O2 -> PCM (Injector Control) loop is already closed before that point, and that tail pipe leak wouldn't have anything to do with the control system regulating nozzle pulsing.

4. How can I check my throttle body system to make sure excess air isn't getting in there?

I'm pretty much at the point where I'm going to try the sensors, but I wanted some opinions here first before I spend money.

PS I've been running injector cleaner as well, it seems to be helping, I was clearing the alarms and hoping that it was just dirty nozzles, but they return after about 20 min.

Any help is appreciated, thanks in advance.

 

Quick update, found someone here at work with a more advanced code reader that actually pipes into software onto the laptop. The O2 sensor readings for the b1s1 and b2s1 were varying wildly between 50mv - 950mv, in idle and operation. While the post catalytic converter was steady and showed the air increase and decrease.

I think I'm almost positive it's the O2 sensors, now If I can just get them off, they are rusted in bad.

BTW I also tried with the MAF disconnected, immediately this made a huge difference, I think open loop operation is what is happening with the MAF disconnected.