2010 LC Misfires on 1 and 8

[mdgaertner]

Hey folks — hoping to tap the collective wisdom here.
I’m chasing a stubborn misfire issue on my 2010 Land Cruiser 200 (3UR-FE 5.7L V8, ~130k miles).

For background, my SAI system has been non-functional for a while. I replaced it once, but I live in a coastal environment and it failed again fairly quickly, so I’ve been living with the SAI codes.

What’s going on:​

This all started as an intermittent misfire on cylinder 1 with a rough idle. After a minute or two, if I shut the engine off and restarted it, the misfire would go away and it would run normally.

What I’ve done so far:​

• Replaced the coil on cylinder 1 → no change
• Replaced the spark plug on cylinder 1 → no change
• Replaced the injector on cylinder 1 → misfire on 1 went away, but then I started
  getting a consistent misfire on cylinder 8
• After that, misfires began roaming between cylinders 1, 4, 7, and 8

At that point, I started looking for vacuum issues:

• Checked breather hoses and found some hoses cracked at the ends
• Replaced all breather hoses and clamps
• Checked the PCV valve (no rattle), replaced the PCV and its hose & clamps

Still had a misfire on 8, so:

• Swapped coil 8 with coil 7 → misfire followed
• Replaced the coil on cylinder 7
• Went back and carefully checked that all coil connectors were fully seated

Current status:​

• Now consistently getting P0301 and P0308 misfire on 1 and 8, one will go away after restarting
• Did an ECU reset:
  • Battery disconnected ~10 minutes
  • Idle 10 minutes with A/C off
  • Idle 2–3 minutes with A/C on
  • Drove ~20 minutes

It’s better than before, but still runs rough at idle and will misfire under load (especially climbing hills at lower RPM).

Looking for ideas:​

At this point I’m wondering what I might be missing — wiring, grounds, compression, something specific to the 3UR-FE that others have seen?

Any insight or next-step suggestions would be greatly appreciated.

Thanks in advance — this one’s been a head-scratcher.

 

[TimCFJ40]

I'd do 2 things that are fairly easy:
1) Replace all spark plugs with OEM plugs. This assumes as listed above you haven't done all of them yet. This is cheap and easy and a good place to start. At 130k miles you're due. I had misfires and a bad coil on my previous 2008, and found that the plugs were well worn. Once the plugs were replaced and the bad coil was replaced with a new TOYOTA OEM Coil, no further misfires.
2) Get a cheap Borescope and look in the cylinders while you are doing the plugs and look for coolant, particularly on cylinders 1 and 8. Coolant in the cylinders indicates a bad head gasket.

From there you at least have ruled out one very easy culprit and one much worse one.

 

[rexington14]

Are you losing coolant? I'd verify the head gasket (pressure test cooling system and borescope cylinders per above and/or block tester and/or compression test and/or leakdown test and/or oil analysis, etc) before throwing any more parts because if that's blown you may be done with this car.

 

[TeCKis300]

Sounds like quite the riddle.

Fueling sounds suspect with the nature of the symptoms.

I would check the fuel pump and fuel driver. Here's some hints

Thread 'DIY Fuel Pump Replace'

Aug 8, 2022

Replaced a fuel pump recently as part of resolving an idle fuel pressure issue. Diagnostic thread here:

P0171: System too Lean (Fuel Trim)

forum.ih8mud.com

Didn't find much documentation on this site so here's my attempt for future reference.

Couple strategies to do this. From above through the cabin access hatch, or below via dropping the tank. Having done this, dropping the tank is the way to go. Avoids cutting the body to enlarge the access hole. Then inevitable fight with the tight retention ring. Quicker and easier, albeit messier and working...

• TeCKis300
• Replies: 20
• Forum: 200-Series Cruisers

• 

 

[GrouchyTech]

Sounds like quite the riddle.

Fueling sounds suspect with the nature of the symptoms.

I would check the fuel pump and fuel driver. Here's some hints

Thread 'DIY Fuel Pump Replace'

Aug 8, 2022

Replaced a fuel pump recently as part of resolving an idle fuel pressure issue. Diagnostic thread here:

P0171: System too Lean (Fuel Trim)

forum.ih8mud.com

Didn't find much documentation on this site so here's my attempt for future reference.

Couple strategies to do this. From above through the cabin access hatch, or below via dropping the tank. Having done this, dropping the tank is the way to go. Avoids cutting the body to enlarge the access hole. Then inevitable fight with the tight retention ring. Quicker and easier, albeit messier and working...

• TeCKis300
• Replies: 20
• Forum: 200-Series Cruisers

• 

Agreed. Check fuel supply, if that’s good then move on to pressure test the cooling system and check cylinders with a borescope.

 

[Sandroad]

If I read this correctly, you have all original plugs on #2-8 and all original coils on #2-6 and 8. Given that, I would take the advice of @TimCFJ40 and get all new OEM plugs and a new OEM coil on #8. Is there any chance you used a cheap aftermarket coil on #1 ? Misfires under load or cold start could very well be wimpy plugs/coils.

I'll bet 2 head gaskets didn't fail at the same time, so look elsewhere in spark or fuel.

What will the consistent SAI codes do to engine operation? I know it operates in the exhaust system, but I wonder if the ECU does not like the constant codes?

 

[TimCFJ40]

If I read this correctly, you have all original plugs on #2-8 and all original coils on #2-6 and 8. Given that, I would take the advice of @TimCFJ40 and get all new OEM plugs and a new OEM coil on #8. Is there any chance you used a cheap aftermarket coil on #1 ? Misfires under load or cold start could very well be wimpy plugs/coils.

I'll bet 2 head gaskets didn't fail at the same time, so look elsewhere in spark or fuel.

What will the consistent SAI codes do to engine operation? I know it operates in the exhaust system, but I wonder if the ECU does not like the constant codes?

I do know the SAI codes cut power and send the vehicle into limp mode, at least they did on mine. This is reportedly because the SAIS codes cause the aip valves not to close at higher temperature, and subject the parts of the SAIS system behind the valves to abnormal temperatures. If the vehicle is getting operated regularly bypassing the SAIS codes, I suppose it's possible that condition causes misfires due to fuel trims being off from the SAIS System working improperly.
I almost suggested the Hewitt Tech kit for fixing the SAIS codes, but you do run the risk of it NOT fixing the misfiring, and being out $400 even if it fixes the SAIS codes. But even the Hewitt Tech Kit, one Coil, and 8 Plugs is perhaps cheap compared to the fix for other issues. It's also hard with modern vehicles to separate out system effects, so solving for the misfires without fixing the SAIS issues may be very difficult.