Working through this and could use the hive minds support. P0171: System too Lean (Fuel Trim). Also P0300: Random/mulitple Cylinder misfire detected. Multiple specific cylinder misfires P030x.
Symptoms: In diagnostics after getting home. LT fuel trim on both banks at idle are high. +15 and +18. LT trims are only incrementally elevated at higher engine speeds/loads (+4/+4 at WOT), so trim is inversely proportional to load. Initial suspicion is a vacuum leak, but didn't find any in cursory troubleshooting. Cleaned MAF and is not the issue. LX570 is a 2009 with 140k. Note I reset all codes after initial issue below, and they have yet to re-appear but presume they will when the engine is really heat soaked idling.
First noticed the issue on a off-road run on a 95 degree day. Idling over 30 minutes, on a really steep 30 degree incline with A/C running, 3/4 tank fuel. Stepped away with kid asleep to help spot buddies over obstacles. Came back to the car noticeably stumbling at idle, with CELs above, barely power to climb to a safer spot, before troubleshooting. Stopped engine, let cool for 10 minutes, restarted and reset codes, and ran fine. Up the trail, and idled probably 10 minutes on another occasion on flatter ground and minor codes came back. Reset. Avoided extended idling through rest of trip and was fine.
Since this issue manifests in both banks, it's likely something that affects both. Could still be a vacuum leak that I haven't found as the symptoms support that. Not MAF, not PCV. I need to work isolating vacuum leaks more systemically but it's a straightforward vacuum system and I didn't see or find any with propane trying to affect fuel trims. There's not much on these boards to show any systemic issues on the 200-series.
I have a new fuel pump in hand and may attack that but wanted to see if anyone had any ideas?
TL;DR - Repair here
forum.ih8mud.com
Symptoms: In diagnostics after getting home. LT fuel trim on both banks at idle are high. +15 and +18. LT trims are only incrementally elevated at higher engine speeds/loads (+4/+4 at WOT), so trim is inversely proportional to load. Initial suspicion is a vacuum leak, but didn't find any in cursory troubleshooting. Cleaned MAF and is not the issue. LX570 is a 2009 with 140k. Note I reset all codes after initial issue below, and they have yet to re-appear but presume they will when the engine is really heat soaked idling.
First noticed the issue on a off-road run on a 95 degree day. Idling over 30 minutes, on a really steep 30 degree incline with A/C running, 3/4 tank fuel. Stepped away with kid asleep to help spot buddies over obstacles. Came back to the car noticeably stumbling at idle, with CELs above, barely power to climb to a safer spot, before troubleshooting. Stopped engine, let cool for 10 minutes, restarted and reset codes, and ran fine. Up the trail, and idled probably 10 minutes on another occasion on flatter ground and minor codes came back. Reset. Avoided extended idling through rest of trip and was fine.
Since this issue manifests in both banks, it's likely something that affects both. Could still be a vacuum leak that I haven't found as the symptoms support that. Not MAF, not PCV. I need to work isolating vacuum leaks more systemically but it's a straightforward vacuum system and I didn't see or find any with propane trying to affect fuel trims. There's not much on these boards to show any systemic issues on the 200-series.
I have a new fuel pump in hand and may attack that but wanted to see if anyone had any ideas?
TL;DR - Repair here
DIY Fuel Pump Replace
Replaced a fuel pump recently as part of resolving an idle fuel pressure issue. Diagnostic thread here: https://forum.ih8mud.com/threads/p0171-system-too-lean-fuel-trim.1289672/ Didn't find much documentation on this site so here's my attempt for future reference. Couple strategies to do...

Last edited: