5.3L Issue - P0171/174/300
02-02-2017, 09:20 PM
#1
5.3L Issue - P0171/174/300 Hey Guys -
Hope you take mercy on me as this is not in my Fbody but actually in a 2003 Yukon I just picked up two days ago - I've been looking on the truck forums, but i feel like you all know the 5.3 better than anyone. Seems to be a well maintained vehicle, has 122k on the clock.
Truck had been running great for two days, then suddenly starts idling very rough on the commute home this evening. Soon enough SES comes on....goes off...comes on...and continued that way the whole way home.
Above 1500 RPM, the light never came on and the truck ran well. Below that, especially below 800-1000 RPM it started being really rough again.
Got it home, scanned it, and had P0171 and P0174 codes. I cleared those and P0171 came back almost instantly.
Ran it for a while, sprayed starting fluid around the intake looking for a leak. Found nothing at all with that check - no noticeable leak. Rescanned and had P0171 & P0174 again and newly, P0300.
I cleaned the MAF with the correct CRC cleaner - no impact to idle and still throws P0171. I then cleared the codes again and completely disconnected the MAF...while it's not idling perfect, it's MUCH smoother than it was, albiet, at about 800 RPM. Also, the exhaust smell is VERY strong with the MAF unplugged. Lastly, the ONLY code to pop up with the MAF disconnected was the MAF code (don't recall what it was). The P0171, P0174, and P0300 didn't return immediately. I ran it for about 2 mins until my eyes were burning from the exhaust.
Thing is, be it a warm or semi-warm (Call it like 160-170*) start, the truck fires up like a champ, idles great, and then 15-30 seconds in starts going to hell. Being that it starts up smoothly, and idles fine for a few seconds before getting crappy, I am assuming this is a sensor issue and most likely not mechanical/electrical like a vacuum leak, bad plug/coil, etc. It also doesn't stumble when giving it gas - it revs right up and seems perfectly fine until idle drops back down to 1k rpm or so.
Does this seem to indicate a bad MAF? If so, are Delphi replacements good or would you go only Delco (I've read many of the Delcos come with a Delphi in the box anyway)
Am I way off with the MAF and would you start somewhere else? I'd really appreciate your input. Trying to keep from pissing the wife off too much by throwing parts at it within 2 days of buying it.
Hope you take mercy on me as this is not in my Fbody but actually in a 2003 Yukon I just picked up two days ago - I've been looking on the truck forums, but i feel like you all know the 5.3 better than anyone. Seems to be a well maintained vehicle, has 122k on the clock.
Truck had been running great for two days, then suddenly starts idling very rough on the commute home this evening. Soon enough SES comes on....goes off...comes on...and continued that way the whole way home.
Above 1500 RPM, the light never came on and the truck ran well. Below that, especially below 800-1000 RPM it started being really rough again.
Got it home, scanned it, and had P0171 and P0174 codes. I cleared those and P0171 came back almost instantly.
Ran it for a while, sprayed starting fluid around the intake looking for a leak. Found nothing at all with that check - no noticeable leak. Rescanned and had P0171 & P0174 again and newly, P0300.
I cleaned the MAF with the correct CRC cleaner - no impact to idle and still throws P0171. I then cleared the codes again and completely disconnected the MAF...while it's not idling perfect, it's MUCH smoother than it was, albiet, at about 800 RPM. Also, the exhaust smell is VERY strong with the MAF unplugged. Lastly, the ONLY code to pop up with the MAF disconnected was the MAF code (don't recall what it was). The P0171, P0174, and P0300 didn't return immediately. I ran it for about 2 mins until my eyes were burning from the exhaust.
Thing is, be it a warm or semi-warm (Call it like 160-170*) start, the truck fires up like a champ, idles great, and then 15-30 seconds in starts going to hell. Being that it starts up smoothly, and idles fine for a few seconds before getting crappy, I am assuming this is a sensor issue and most likely not mechanical/electrical like a vacuum leak, bad plug/coil, etc. It also doesn't stumble when giving it gas - it revs right up and seems perfectly fine until idle drops back down to 1k rpm or so.
Does this seem to indicate a bad MAF? If so, are Delphi replacements good or would you go only Delco (I've read many of the Delcos come with a Delphi in the box anyway)
Am I way off with the MAF and would you start somewhere else? I'd really appreciate your input. Trying to keep from pissing the wife off too much by throwing parts at it within 2 days of buying it.
02-12-2017, 01:21 PM
#2
Teching In
Join Date: Sep 2016
Location: North Carolina
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2003 Avalanche here brother with the 5.3
Check your fuel pressure regulator on the intake, they go bad a lot and will throw that code. Mine was doing the same thing only it was hard to start sometimes. I put a test gauge on the Schrader valve on the intake manifold and had only 30psi of fuel pressure. I ended up replacing my fuel pump. Now I have 59psi and runs great!!!
If it was me I would check your fuel pressure. It needs to be in the 57-60 psi range for the truck to run correct. If you have good pressure then I would look at the pressure regulator it is also located on the intake manifold. Changing the fuel filter will not hurt also.
P0174 and P0171 codes are lean condition in the left and right bank. Lean is from lack of fuel or air leak. Also look over all your rubber hoses to make sure they are not cracked or worn. They will also throw a lean code.
Hope that helps
Check your fuel pressure regulator on the intake, they go bad a lot and will throw that code. Mine was doing the same thing only it was hard to start sometimes. I put a test gauge on the Schrader valve on the intake manifold and had only 30psi of fuel pressure. I ended up replacing my fuel pump. Now I have 59psi and runs great!!!
If it was me I would check your fuel pressure. It needs to be in the 57-60 psi range for the truck to run correct. If you have good pressure then I would look at the pressure regulator it is also located on the intake manifold. Changing the fuel filter will not hurt also.
P0174 and P0171 codes are lean condition in the left and right bank. Lean is from lack of fuel or air leak. Also look over all your rubber hoses to make sure they are not cracked or worn. They will also throw a lean code.
Hope that helps
02-14-2017, 02:35 PM
#3
Thanks man - I appreciate it! For documentation purposes, it was my O2 B1S1. Was reading lean and dumping fuel. I ended up changing both upstream O2's, my plugs (driver's side was crusty from the rich condition; passenger looked great), and wires. I also did the fuel filter.
That being said, I am still throwing a P0300 on occasion....and I do believe my fuel pump is on it's way out. It's steady, but only about 50PSI IIRC at key on, engine off....and 40ish with the engine running. I have a few other symptoms that make me believe the pump is beginning to crap out.
That being said, I am still throwing a P0300 on occasion....and I do believe my fuel pump is on it's way out. It's steady, but only about 50PSI IIRC at key on, engine off....and 40ish with the engine running. I have a few other symptoms that make me believe the pump is beginning to crap out.
02-15-2017, 08:02 AM
#4
I just changed the intake gaskets on my 99 1500 with a 5.3. it's quite common on the truck engines. Mine would run like dog **** down low every winter, terrible idle, surge at stops. Just slapped the new gaskets on Sunday and it's like a totally different truck. I thought it stalled a few times coming to a stop because it was smooth again lol.
I initially thought it was an o2 sensor or fuel pump until I hooked hptuners up to it. Noticed it was 25% lean down low and at idle only. Did some research and realized it's super common, instantly ordered the new ones and bam!
Edit: mine would also do the same thing when it was warm out or the engine was warm. I figured it to be less dense air coming in through the leak when it's warm under the hood and or outside. I too was getting the lean on both banks code, only in the winter time though.
I initially thought it was an o2 sensor or fuel pump until I hooked hptuners up to it. Noticed it was 25% lean down low and at idle only. Did some research and realized it's super common, instantly ordered the new ones and bam!
Edit: mine would also do the same thing when it was warm out or the engine was warm. I figured it to be less dense air coming in through the leak when it's warm under the hood and or outside. I too was getting the lean on both banks code, only in the winter time though.