Rough Idle, smells rich, P0171 and P0174 codes on 5.3L

[shortboxin]

Doesn't idle well, smells rich and backfires a lot. I get P0171 and P0174 lean codes. Fuel trims at idle are all 25%.

The original engine I swapped into my truck was a 2004 4.8L with a VIN V. The replacement engine is a 2004 5.3L with a VIN Z (flex fuel). I am using the 4.8L injectors, throttle body, and computer on the 5.3L engine.

Is using the VIN V 4.8L computer on my VIN Z 5.3L likely causing the lean codes? I did swap my MAF, no change.

 

[Sad Sack]

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[Ricko1966]

Lean code,rich smell. feel the exhaust for cold cylinders if you can those will be your issue. First thing I'd look at is ignition. Or exhaust leak. Here's how this works your cylinder doesn't light off for what ever reason. Now you can smell the 1 part unburned fuel,but the computer is reading the 14 parts of air that just went through the engine unchanged. So it sees lean. Also if you have an exhaust leak that can let atmospheric air get pulled past the O2 sensor it's going to read that oxygen,read lean and richen the mixture.

 

[Vbb199]

Use a infrared thermometer, point it at each primary and tell us if one of them is cold or unusually hotter

 

[Ricko1966]

Use a infrared thermometer, point it at each primary and tell us if one of them is cold or unusually hotter

I wet my hand and touch them very briefly the ones that don't sizzle are the problems. I started doing this back in 1985 I don't even think they had infrared thermometers back then. If you have an infrared thermometer by all means use it. But now a bunch of you just learned a quick cheater trick.
P.S. you do have to be quick.

 

[shortboxin]

Thank you so much for all of the input! I did discover part of the issue.

I never connected my breather nipple on the passenger bank as I didn't consider it important yet. I squeezed the pcv hose on the driver bank and heard the idle improve so I plugged the breather nipple momentarily and got the same result. I made the necessary mod to my intake tubing and got a metered hose connected to the breather nipple. This greatly improved the idle and no backfiring anymore. Also, fuel trim now normal on bank 1.

I did use an infrared thermo yesterday, but it wasn't full temp yet as I was only getting around 180 deg F at each header port.

I just realized that I left SOME VERY IMPORTANT INFO OUT WHEN I POSTED THIS. I just changed the intake prior to this issue and the engine only had one drive on it (6 months ago), so I didn't have a good baseline on anything.

I did spray starter fluid around intake ports and injectors yesterday before connecting the breather port. The idle would intermittently improve very slightly. I'll try it again today and I'll get it to full temp and check the exhaust ports as well.

Thanks again!

 

[shortboxin]

Shot it with some starter fluid around all intake ports and injectors, no noticeable change in idle.

Unplugged Bank 1 O2 sensor to see how the PCM would respond. I suspected that Bank 1 ST fuel trims would somehow change. Instead what I saw was Bank 2 ST fuel trim went to 0% from 25%. I then thought maybe Bank 1 was actually reporting Bank 2 to the PCM and vise versa. Checked my PCM connections for signal + and signal - for both banks (all good), so maybe if one O2 becomes disconnected, the PCM automatically scales back fuel trim?

Also checked all exhaust port temps using my infra red. Everything reading between 170-195 degrees between all ports with engine around 180 degrees coolant temp. I'm running Chinese shorty headers, not cast manifolds (don't know if this matters).

 

[Vbb199]

If its showing super lean theres a good chance its an exhaust leak, or a serious misfire... either one will appear as lean conditions

Unless you got a dead injector... but your temp check would reveal that, which apparently came back fine

 

[shortboxin]

Double checked all of my passenger header and collector bolts and torqued up a little more just in case. Ran the truck with the code scanner. Looked at real time data and discovered that not only is my bank 2 fuel trim extremely high at idle at 26.6%, but the O2S21 is reading 0V. My bank 1 fuel trim moves around, but is typically very low under 5% and the O2S11 reads around 700mV. Is it even possible to have 0V? Shouldn't it be in the millivolt range?

Unplugged my computer again and verified continuity from my O2 Signal Hi and Low for both banks to the PCM (all good) and checked each pin to all other pins on the PCM for shorts as well (nothing found). I'm dealing with a Chinese harness here, so I did a lot of searching online trying to figure out which wires I should be checking. I finally made a judgement call based on some color matching combined with pinouts online.

Signal Hi = PUR (China) to LT BLU (O2)
Signal LO = WHT (China) to WHT (O2)

The other two wires were BLK on the O2.

Am I right on this? I also tried to read a voltage on the Signal Hi to GND for both banks at idle. Bank 1 was flashing all over the place on my DMM from 200mV to 1.2V while bank 2 was a fairly steady 50mV to 60mV. Don't know if that was a floating value or what because the PCM displays 0V for O2S21 which I assume is the value read from the O2 Signal Hi to GND.

Last, but not least, I sprayed starting fluid around my passenger intake ports, runners, and injectors. Rock solid idle.

Besides a smoked PCM, I'm out of ideas. Keep in mind that when I first started this truck, there were a lot of miswires that this PCM endured, so it could have gotten smoked...

Thanks for all your help!

 

[shortboxin]

I get the feeling no one is reading this anymore, but just in case anyone is...

I bought extension harnesses to connect the bank 1 O2 to the bank 2 PCM harness connection and vise versa.

Started up the truck and read real time data. with it connected normally. I then swapped the O2s so that bank 1 fed bank 2 and bank 2 fed bank 1. Here are the results:

STD (bank 1 to 1 and bank 2 to 2)

O2S11 800mV range

O2S21 0.00V


SWAPPED (bank 1 to 2 and bank 2 to 1)

O2S11 800mV range

O2S21 0.00V

The fact that the values didn't change at all on my scanner when swapped indicates that the O2 is outputting a legit value on bank 2 since bank 1 is reading the same value, right? That makes me think that I've either got a weird wiring issue of some sort or the PCM is smoked. Any thoughts?

 

[shortboxin]

Please refer to my new post. I put all information in the new post so it's easier to follow.

 

[Camar068]

just noticed this post. I've had the same lean condition (both banks) as you since 2 years ago after putting a 4.8 engine in place of a LS swap 5.3. The 4.8 died, so I rebuilt the 5.3. Still getting the same codes. All I did was change the block/heads (no pcm/harness/intake...nothing but the long block).

I've changed MAF, fuel pump, regulator, ohm'd wires from pcm to MAF.

Something that may help you. Years ago early in the swap, I got the O2 sensor wires backwards. It would not idle well at all at a light, but as soon as I took off hard it ran normal. For that issue I figured out that one o2 sensor had a purple wire and the other had a purple/white wire.....I had them backwards. Link/chart below, blue connector pin 66 area are the O2 sensors.

LT1 swap 2004 -2007 pin outs

 

[Ricko1966]

Doesn't idle well, smells rich and backfires a lot. I get P0171 and P0174 lean codes. Fuel trims at idle are all 25%.

The original engine I swapped into my truck was a 2004 4.8L with a VIN V. The replacement engine is a 2004 5.3L with a VIN Z (flex fuel). I am using the 4.8L injectors, throttle body, and computer on the 5.3L engine.

Is using the VIN V 4.8L computer on my VIN Z 5.3L likely causing the lean codes? I did swap my MAF, no change.

Does the problem happen hot and cold? Just hot? Just cold? If it happens cold look at what all is not in play during open loop. You can ignore those items.

 

[Camar068]

just noticed this post. I've had the same lean condition (both banks) as you since 2 years ago after putting a 4.8 engine in place of a LS swap 5.3. The 4.8 died, so I rebuilt the 5.3. Still getting the same codes. All I did was change the block/heads (no pcm/harness/intake...nothing but the long block).

I've changed MAF, fuel pump, regulator, ohm'd wires from pcm to MAF.

Something that may help you. Years ago early in the swap, I got the O2 sensor wires backwards. It would not idle well at all at a light, but as soon as I took off hard it ran normal. For that issue I figured out that one o2 sensor had a purple wire and the other had a purple/white wire.....I had them backwards. Link/chart below, blue connector pin 66 area are the O2 sensors.

LT1 swap 2004 -2007 pin outs

update to my issue. Turns out the 2 MAF sensors from Autozone (2 yrs ago, duralast) were bad. On a whim, I changed the maf to a Delphi and my codes are gone and my LTFT's are down to ~5% at idle from a constant 25% before. We'll see how much of a warranty is on the AZ maf.....be nice to get money back. Cost to me for this is at least $290 for the fuel pump, o2 sensors and regulator/filter.

Good thing is I have a good fuel pump, regulator and 02 sensors.

Hope this helps someone else.

 

[Bextreme04]

update to my issue. Turns out the 2 MAF sensors from Autozone (2 yrs ago) were bad. On a whim, I changed the maf to a Delphi and my codes are gone and my LTFT's are down to ~5% at idle from a constant 25% before. We'll see how much of a warranty is on the AZ maf.....be nice to get money back. Cost to me for this is at least $290 for the fuel pump, o2 sensors and regulator/filter.

Good thing is I have a good fuel pump, regulator and 02 sensors.

Hope this helps someone else.

There are different MAF's... chances are you had the wrong ones for the programming in the PCM. If you don't have the intake piping that the PCM was tuned for it will also be off... just not full rich/lean off. Part of a standard tuning procedure is to tune the MAF once you get the VE map properly adjusted with the MAF failed.