24yo LC 100 series owner looking for diagnosis advice

[i know u rider]

Hey all — long post but I want to give enough context for someone to actually help.
I am 24yo, this is my first rig and first forum post.

I have a 2003 Land Cruiser 100 Series, 2UZ-FE, currently sitting at about 217k miles. I'm based in central CT and planning a cross-country drive to Utah this winter for ski season — roughly 15-20k miles of driving over the season. I love this truck and would love nothing more than to take it. But I've had a recurring misfire situation over the past several months that I've been chasing, and causing a ton of frustration as a daily driver and before I commit to the trip I want someone who knows the 100-Series well to put eyes on it, give it a thorough going-over, and tell me honestly whether they'd feel comfortable taking it cross-country — or whether I might wanna move on given the circumstances


I will not be offended if the answer is "sell it." However, if I’m in this forum I doubt that is ever the advice!!
---
Recent Major Work (for context):
- Timing belt + water pump: Nov 2024 (~196k)
- Valve cover gaskets + all 10 spark plug tube seals: Apr 2026 (~215k) — Toyota dealer
- All 8 ignition coils replaced with OEM Toyota: Apr 2026 (~215k) — Toyota dealer
- IGT2 wire to ECU soldered/replaced: May 2026 (~215k) — Toyota dealer
- Fuel filter: Jul 2026 (~216k)
- New battery (upgraded group size): Jul 2026
- New tires (Michelin Defender LTX 275/60R18): Jun 2025 (~204k)
- Front brakes + rotors: Nov 2024
Roughly $12k into the truck over the past 18 months.
---
The Misfire Issue — Full Timeline:
This is the part I need help with. Starting Feb 2026, I developed a recurring rough intermittent misfire pattern that has been difficult to pin down.
Here's the sequence:

- Feb/Mar 2026: P0354 (Coil D circuit). Local shop replaced ignition coil #4 with aftermarket Coil, cleaned throttle body. Resolved briefly then returned within a week asP0300/P0301/P0302/P0303/P0304/P0307/P0308 — widespread misfires. MAF reinstalled (no charge). Ran fine one day, failed the next morning with weak crank, surging RPMs, engine cutting out, transmission lurching. New codes P0352, P0353. MAF replaced again with different brand.
- Apr 2026: Brought to Toyota dealer. Tech found: aftermarket coils on multiple cylinders, cylinder 2 coil severely burnt, oil residue in spark plug tubes from leaking tube seals. Wiring from ECU to coils tested normal at time of inspection. Replaced all 8 coils with OEM Toyota, both valve cog tube seals. ~$2,750. Drivability improved noticeably — stronger idle, better starts.
- Late Apr 2026: P0352 returned about a week later (Coil B primary circuit open). Came on during a cold start, turned off on its own, returned a few days later.
- May 2026: Back to Toyota dealer. Tech found P0352 stored but not active. Measured resill testing normal at the time. Identified intermittent open circuit on IGT2 wire betweenECU connector E5 pin 8 and I2 pin 3. Soldered in a new IGT2 wire. No codes after repair. ~$438.
- Jul 2026: P0300, P0301, P0306 (cylinders 1 and 6 misfiring) + P0446. Local shop changesed to try Seafoam before swapping more parts. Since the fuel filter change (~6 weeksago), no misfire codes have returned. Running well currently. Only active code is P0446, which I've been clearing.
My read on the pattern: The local shop kept replacing parts (MAF twice, one aftermarket coil) without resolving it. Toyota dealer found the real issues — oil-contaminated coil area and a failing IGT2 wire.
The fact that misfires on cylinders 1 and 6 showed up after the IGT2 repair is suspiciou those two cylinders on the 2UZ-FE. Whether the July misfires were fuel-related (fixed byfilter) or early IGT1 degradation, I'm not sure. The harness is 20+ years old and has been physically disturbed multiple times during all the intake/MAF work.
Current open items:
- P0446 (EVAP vent control) — present on and off for ~2 years, never properly fixed
- Spark plugs — Toyota notes from May confirm aftermarket plugs were still in the engine at that visit. No record of OEM replacements since. This may still be open.
- IGT1/3/4 wire condition — unknown. IGT2 was repaired. The rest were "testing normal" i that's already shown one failure.
---
What I'm Looking For:
1. Thorough pre-trip inspection — brakes, fluids, cooling system, steering, driveline (front/rear diff, transfer case, CV boots), belts, hoses, anything you'd want sorted before 15-20k miles including
mountain driving at altitude in winter conditions.
2. Fresh eyes on the misfire history — I want someone who knows the 2UZ-FE well to look at this pattern and tell me whether the truck is actually fixed or whether I'm one cold morning away from another
no-start. Specifically whether the remaining IGT wires should be inspected/replaced proaanything pointing to injectors, fuel delivery, or ECU that hasn't been properly ruled out.
3. Honest "fix or sell" opinion — I've put ~$12k in over 18 months. The truck has about $15-17k in market value if running clean. I'm not going to be offended by a straight answer. If a knowledgeable person
looks at this and says "the wiring harness is going to keep giving you grief and this isolo winter XC trip," I want to hear that.
---
Location: Central CT. Will travel within reason — someone recommended Toyota Performance Center in New Milford and I'm not opposed to making that drive if they're worth it.
Any shop recommendations or specialists in the CT area (or western MA/RI) who know the 100 Series well would be hugely appreciated. Happy to share the full service records. Thanks in advance.

 

[i know u rider]

Hey all — long post but I want to give enough context for someone to actually help.
I am 24yo, this is my first rig and first forum post.

I have a 2003 Land Cruiser 100 Series, 2UZ-FE, currently sitting at about 217k miles. I'm based in central CT and planning a cross-country drive to Utah this winter for ski season — roughly 15-20k miles of driving over the season. I love this truck and would love nothing more than to take it. But I've had a recurring misfire situation over the past several months that I've been chasing, and causing a ton of frustration as a daily driver and before I commit to the trip I want someone who knows the 100-Series well to put eyes on it, give it a thorough going-over, and tell me honestly whether they'd feel comfortable taking it cross-country — or whether I might wanna move on given the circumstances


I will not be offended if the answer is "sell it." However, if I’m in this forum I doubt that is ever the advice!!
---
Recent Major Work (for context):
- Timing belt + water pump: Nov 2024 (~196k)
- Valve cover gaskets + all 10 spark plug tube seals: Apr 2026 (~215k) — Toyota dealer
- All 8 ignition coils replaced with OEM Toyota: Apr 2026 (~215k) — Toyota dealer
- IGT2 wire to ECU soldered/replaced: May 2026 (~215k) — Toyota dealer
- Fuel filter: Jul 2026 (~216k)
- New battery (upgraded group size): Jul 2026
- New tires (Michelin Defender LTX 275/60R18): Jun 2025 (~204k)
- Front brakes + rotors: Nov 2024
Roughly $12k into the truck over the past 18 months.
---
The Misfire Issue — Full Timeline:
This is the part I need help with. Starting Feb 2026, I developed a recurring rough intermittent misfire pattern that has been difficult to pin down.
Here's the sequence:

- Feb/Mar 2026: P0354 (Coil D circuit). Local shop replaced ignition coil #4 with aftermarket Coil, cleaned throttle body. Resolved briefly then returned within a week asP0300/P0301/P0302/P0303/P0304/P0307/P0308 — widespread misfires. MAF reinstalled (no charge). Ran fine one day, failed the next morning with weak crank, surging RPMs, engine cutting out, transmission lurching. New codes P0352, P0353. MAF replaced again with different brand.
- Apr 2026: Brought to Toyota dealer. Tech found: aftermarket coils on multiple cylinders, cylinder 2 coil severely burnt, oil residue in spark plug tubes from leaking tube seals. Wiring from ECU to coils tested normal at time of inspection. Replaced all 8 coils with OEM Toyota, both valve cog tube seals. ~$2,750. Drivability improved noticeably — stronger idle, better starts.
- Late Apr 2026: P0352 returned about a week later (Coil B primary circuit open). Came on during a cold start, turned off on its own, returned a few days later.
- May 2026: Back to Toyota dealer. Tech found P0352 stored but not active. Measured resill testing normal at the time. Identified intermittent open circuit on IGT2 wire betweenECU connector E5 pin 8 and I2 pin 3. Soldered in a new IGT2 wire. No codes after repair. ~$438.
- Jul 2026: P0300, P0301, P0306 (cylinders 1 and 6 misfiring) + P0446. Local shop changesed to try Seafoam before swapping more parts. Since the fuel filter change (~6 weeksago), no misfire codes have returned. Running well currently. Only active code is P0446, which I've been clearing.
My read on the pattern: The local shop kept replacing parts (MAF twice, one aftermarket coil) without resolving it. Toyota dealer found the real issues — oil-contaminated coil area and a failing IGT2 wire.
The fact that misfires on cylinders 1 and 6 showed up after the IGT2 repair is suspiciou those two cylinders on the 2UZ-FE. Whether the July misfires were fuel-related (fixed byfilter) or early IGT1 degradation, I'm not sure. The harness is 20+ years old and has been physically disturbed multiple times during all the intake/MAF work.
Current open items:
- P0446 (EVAP vent control) — present on and off for ~2 years, never properly fixed
- Spark plugs — Toyota notes from May confirm aftermarket plugs were still in the engine at that visit. No record of OEM replacements since. This may still be open.
- IGT1/3/4 wire condition — unknown. IGT2 was repaired. The rest were "testing normal" i that's already shown one failure.
---
What I'm Looking For:
1. Thorough pre-trip inspection — brakes, fluids, cooling system, steering, driveline (front/rear diff, transfer case, CV boots), belts, hoses, anything you'd want sorted before 15-20k miles including
mountain driving at altitude in winter conditions.
2. Fresh eyes on the misfire history — I want someone who knows the 2UZ-FE well to look at this pattern and tell me whether the truck is actually fixed or whether I'm one cold morning away from another
no-start. Specifically whether the remaining IGT wires should be inspected/replaced proaanything pointing to injectors, fuel delivery, or ECU that hasn't been properly ruled out.
3. Honest "fix or sell" opinion — I've put ~$12k in over 18 months. The truck has about $15-17k in market value if running clean. I'm not going to be offended by a straight answer. If a knowledgeable person
looks at this and says "the wiring harness is going to keep giving you grief and this isolo winter XC trip," I want to hear that.
---
Location: Central CT. Will travel within reason — someone recommended Toyota Performance Center in New Milford and I'm not opposed to making that drive if they're worth it.
Any shop recommendations or specialists in the CT area (or western MA/RI) who know the 100 Series well would be hugely appreciated. Happy to share the full service records. Thanks in advance.

View attachment 4193017

 

[i know u rider]

Attached is a copy of services over time and cost related to this issue.

 

[frawstme]

Sorry if im misunderstanding because it was a bit of a read. Few things- are you confusing IGT with IGF? page 152

another is that your P0301 and P0306 codes don't prove that your ign wire is failing, that would come along with a third code P035x (all together, not some present then p035x later on). I just spent a great deal of time learning about those codes a few weeks ago on mine. Those codes are from plugs or injectors or compression, fuel mixture, grounding issues. Im guessing its plugs and fuel mixture based on some of the other things that you said

you mentioned aftermarket plugs, you should proactively go ahead and replace those with denso. Im surprised that plugs weren't one of the first things that they went after when the misfire codes came up

do you have your short and long term fuel trim readings?

have they done a compression or leak down test?

you said that your 100 is cranking weak, is that just how it feels or have you done actual tests with a multimeter?

lastly do you have tech stream?

im out of state so gonna be slow responding after this message

 

[GTV]

Considering your location, rust will be the deciding factor on whether or not to sell it. Mechanical issues are frustrating but can be sorted out with enough patience.

 

[frawstme]

oh i also just noticed that you later got the P0352 code, that's specific to your #2 coil. you mentioned that IGT2 was replaired, theres a chance that it wasnt repaired correctly but it'd be hard to verify

 

[i know u rider]

Thanks, this is helpful. And no worries on the slow response.
To clarify, the IGT2 wire was the one that Toyota replaced/repaired. That was after the P0352 showed up and they traced the circuit.

I’d like to replace the spark plugs with Denso plugs proactively. I’m surprised they didn’t do them when they replaced all 8 ignition coils, especially given the previous misfire codes.

As far as fuel trims, my STFT and LTFT have looked normal from what I can tell on my code reader. I can pull the actual readings again and post them.

I have not had a compression or leak-down test done yet.


The weak cranking is mostly based on how it feels/sounds. It was noticeably weaker in the past and seems better now, but still doesn’t feel quite as strong as I remember it being. I haven’t actually tested it with a multimeter.

I also don’t have Techstream currently.

oh i also just noticed that you later got the P0352 code, that's specific to your #2 coil. you mentioned that IGT2 was replaired, theres a chance that it wasnt repaired correctly but it'd be hard to verify

Yeah, that's one of the things I'm still wondering about. The IGT2 repair was done by Toyota in May after they traced the PO352 to an intermittent open in that circuit.


The P0352 has not returned since that repair, but in July I did get P0300/P0301/ P0306 — random misfire plus cylinders 1 and 6 - without another P035x code.


Could an intermittent ECU issue still be in play here? Toyota had mentioned the ECU as a possibility before they found/repaired the IGT2 wire. I'm just not sure whether an ECU problem could explain misfires moving around between cylinders without throwing the corresponding P035x circuit codes, or if the July 1/6 misfires point much more toward plugs/injectors/fueling/etc.

Considering your location, rust will be the deciding factor on whether or not to sell it. Mechanical issues are frustrating but can be sorted out with enough patience.

True this is. Vehcile has some surface level rust but has been washed weekly and been painted on regular basis about every year

 

[Super77]

Your issues are bit thick for a forum diagnosis - at least one that I would trust. You're talking about taking a known-problematic, new-to-you vehicle, nearly as old as you are, on a cross-country trip in wintertime. That needs hands-on evaluation. This is the best vehicle forum I've been on, but there's limits to what anyone can do in a thread. You have the right instinct to seek out a local expert.

Also curious about your math: It's about 6,500 miles round-trip between Connecticut and Utah, but you're planning to drive 15-20,000 miles? Are you getting there by way of Alaska? . Honestly, a 100 will burn between $4-5K in gas in covering that, not including any lodging, food, or unexpected repairs and maintenance along the way (which will ALWAYS happen at the most expensive and inconvenient moment). Factor in the pre-trip inspection you're considering, another round of preventative maintenance, and this approaches a $10K+ road trip. Worth it?

Oh, and welcome! I do hope you keep and love the truck - just give the road trip a think.

 

[i know u rider]

Your issues are bit thick for a forum diagnosis - at least one that I would trust. You're talking about taking a known-problematic, new-to-you vehicle, nearly as old as you are, on a cross-country trip in wintertime. That needs hands-on evaluation. This is the best vehicle forum I've been on, but there's limits to what anyone can do in a thread. You have the right instinct to seek out a local expert.

Also curious about your math: It's about 6,500 miles round-trip between Connecticut and Utah, but you're planning to drive 15-20,000 miles? Are you getting there by way of Alaska? . Honestly, a 100 will burn between $4-5K in gas in covering that, not including any lodging, food, or unexpected repairs and maintenance along the way (which will ALWAYS happen at the most expensive and inconvenient moment). Factor in the pre-trip inspection you're considering, another round of preventative maintenance, and this approaches a $10K+ road trip. Worth it?

Oh, and welcome! I do hope you keep and love the truck - just give the road trip a think.

Those are fair points, and I agree this has probably gotten beyond what I can reasonably diagnose through a forum. That’s really why my main goal with the post was finding someone local who knows these trucks well and can put hands on it before I make the decision.

And yeah, I should have worded the mileage part better lol. I wasn’t planning on taking the scenic route through Alaska lol. The 15–20k was my rough estimate for total mileage between now and around this time next year, factoring in normal driving here, the ~4-5 months I’d be living in Utah, driving to/from the mountains and ski areas, the round trip from CT, and then normal driving afterward. The actual cross-country portion is obviously much less.

Your point about cost is something I’m considering though. I know keeping a 217k-mile 100 reliable isn’t free, and the fuel cost over that amount of driving is significant. At the same time, the alternative is selling a truck I know and have already put a lot of maintenance into, then spending considerably more on another vehicle that has its own unknowns/depreciation.


So I think what I’m really trying to determine is whether I’m dealing with a fundamentally solid 100 that has had a frustrating but fixable series of issues, or whether the recent history is evidence that I’m reaching the point where relying on it for that kind of mileage is no longer sensible.

That’s why I’d really value a knowledgeable 100-Series shop to provide a fairly ruthless pre-trip assessment.

If they tell me it needs another $3-5k but that gets me to a truck they’d confidently drive to Utah, that’s one decision.

If they find a bunch of aging systems and tell me I’m likely to keep chasing problems, that’s a very different one.

 

[frawstme]

Yeah, that's one of the things I'm still wondering about. The IGT2 repair was done by Toyota in May after they traced the PO352 to an intermittent open in that circuit.


The P0352 has not returned since that repair, but in July I did get P0300/P0301/ P0306 — random misfire plus cylinders 1 and 6 - without another P035x code.


Could an intermittent ECU issue still be in play here? Toyota had mentioned the ECU as a possibility before they found/repaired the IGT2 wire. I'm just not sure whether an ECU problem could explain misfires moving around between cylinders without throwing the corresponding P035x circuit codes, or if the July 1/6 misfires point much more toward plugs/injectors/fueling/etc.


True this is. Vehcile has some surface level rust but has been washed weekly and been painted on regular basis about every year

In response to this message (you quoted mine and typed in the quote, so it doesn't show):

Replace the spark plugs with the exact denso spec for your model year, it's listed on the label under the hood. make sure you dont just use any generic denso plugs. inspect and label the old plugs that you remove by its bank cylinder..just wondering, do you know how long its been since they were replaced?

post your STFT and LTFT when you get the chance. run the scanner once the car is fully warmed up and steady ~2500 rpm on the pedal

i mentioned the compression test, thats not something you necessarily need to do right now. only if the misfires return

i dont know if i would worry about the slow start if youre making that statement based off feel. Mine feels slow to start too, a lot of these older trucks do. if you have a multimeter, it's a fairly easy test though. if you need me to walk you though that, i can. i just dont feel like thats the issue here unless you have a a grounding issue

you mentioned ECU issues, that could be the cause but i really doubt it. you would get those p0301 and p0306 codes far more often than just an isolated incedent followed by it coming back months later.

if the p0352 code never came back you should (for the time being) assume that they resolved that specific issue

i never addressed it in my first post but the poster above is correct. rust is the deciding factor of if you should continue dumping money into this. spark plugs are cheap, and multimeter tests are basically free, checking your fuel trims are free. i would start with these things. if it reveals a larger issue, and you have a lot of rust under it, probably stop chasing this


edit:
i thought on this more last night, I guess its not that unikely that it's the ECU. Theres just too much going on to decide that's the problem right now, need to narrow things down some.

 

[NE Snowman]

Here it is frank, not willing do your own plugs and coils set you back like $2000. That’s a 1 banana get to know your truck job. Not saying it would’ve fixed your issue but on the $ side an old truck you should be willing to wrench some.

Post in your local clubhouse area asking for help or a local mechanic recommendation. It seems like it might be an electrical gremlin and someone will have to test the harness.

 

[excessive]

if ive read correctly, the spark plugs are still unknown, and that is one of the easiest and cheapest things to try.
i would also make 100% sure the MAF is an OEM toyota one, and tested to confirm it's good.
also, might want to check your fuel pressure - fuel pump may be getting old & tired

 

[Greenpiece]

Right before my fuel pump went out, I had multiple misfire codes. Fuel pump got hot when run for a while: misfire and die. Let it cool off, cruiser ran good. Replaced fuel pump: has run well since.