My 2001 blazer 4dr 4x4 has had very rough idle lately. I have also been experiencing a lack of power starting from 0. It seems to stumble (even stall sometimes) before it moves. I have recently change oil, air filter, fuel filter, fuel pump, and cleaned the MAF. My obd software shows a purge leak test failure and a small vacuum leak failure. However I am not able to find one. Any help would be great!

 

P0171 - Fuel Trim System Lean Bank 1
P0174 - Fuel Trim System Lean Bank 2
P030x - Random/Multiple Cylinder Misfire Detected

The misfire is likely a product of the lean codes. Have you tested the fuel pressure? Do you have any exhaust leaks? When was the last time you had a tuneup (plugs, wires, cap, & rotor)? You can check for vacuum leaks with an unlit propane torch by tracing along the vacuum lines. A vacuum leak could cause the lean codes as well.

 

thanks for the reply! i have all of my tune up parts ready to be installed this weekend. While im at it i will also check for leaks with a prop torch.
EDIT:
Well I just tuned it up today (plugs, wires, cap, rotor) and the fuel pump is a new acdelco so I don't suspect that. It does seem to run much better now. I did also check for vac leaks with carb cleaner and didn't find any. All fluids and filters have also been changed. The only thing I noticed was that the throttle body plate was very dirty. I hope cleaning it will make the truck run even better.

 

replace O2 sensors and thank me later. I had the exact same combination (PO300, PO171, PO174) on my Chevy Avalanche. I replaced the plugs and plug wires (as you said you've just done) and replaced all four O2 sensors (you can probably get away with just the 2 pre-cat if you're trying to save $) and after I did that I cleared the codes, they went away, and the truck ran like the day we drove it off the lot. For $50 per O2 sensor, my bet is that it'll be running great.

I know you probably think it's crazy and totally unrelated to the problem, but I'm tellin' ya, I had the exact same thing. The Avvy had around 200k miles on it and the O2s were ancient, so I think maybe they had gotten so bad that the readings they were giving were so bad that it screwed up the fuel:air ratio.

 

@iamchevyman5
I do remember reading somewhere that it might be a lazy o2 sensor contributing to my problems. Well after driving a few miles with the new plugs, wires, etc., it seemed to be running better but soon started its crap again. I will clean the throttle body and replace the pcv valve (probably won't have any effect but haven't changed them). I'll also give changing the o2 sensors a go. It makes sense that they can be causing the problem. Are all the sensors the same because acdelco.com only has AFS105 listed and if I remember correctly I have 3 in total.

@swartlkk
Those links were very helpful understanding exactly what the problem was.

 

Yes, all 3 sensors are the same. Only the ones closest to the exhaust manifolds, before the 'y' in the y-pipe need to be replaced as the 3rd one is only for catalyst monitoring and has no bearing on fuel delivery.

 

keep us updated, brahh

 

Could this be the cause of my problems? my 96 blazer 4.3 is running rough from the start(0 mph +) and if i'm just cruising at 45 50mph it starts cutting out.

 

justinh4578, You are more than welcome to follow along in this thread, but unless your problem exactly matches the OPs...lets keep your discussion in your thread.

 

lol. Gotcha. Wasnt trying to hijack. Amazon has the AC Delco $39.75 free shipping