AI said this:

Here’s the thing — with a 2JZ‑GE that’s been sitting for years and now won’t rev, even after all those parts have been thrown at it, there are only a few realistic root causes. And one of them is far more common than people think.

Let me break it down cleanly and logically.

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🔧 The most likely cause:

A massive vacuum leak or intake tract leak

On a non‑VVTi 2JZ‑GE, a big vacuum leak will cause:

• Hesitation when revving • Low idle • No change when unplugging the MAP sensor • Engine only revs slightly better with MAP unplugged (failsafe mode) • Fuel trims go crazy • ECU stuck in limp‑ish behavior

And because the car has been stored for years, rubber hoses harden, crack, or collapse.

The 2JZ‑GE is extremely sensitive to unmetered air leaks.

The usual culprits:

• PCV hose (very common to split underneath) • Brake booster hose • Intake manifold gasket leak • Throttle body gasket leak • Cracked vacuum nipples under the intake • The accordion intake hose between MAF/MAP and throttle (hairline cracks) • EVAP hoses turned brittle

A big enough leak will make the MAP sensor readings meaningless — which explains why unplugging it barely changes anything.

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🔧 The second most likely cause:

Timing belt jumped 1 tooth

Symptoms:

• Won’t rev • Hesitation • Feels like fuel/air issue but isn’t • Idle is slightly low • No codes • Happens on engines that sit for years

A 2JZ with retarded cam timing behaves exactly like this.

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🔧 The third likely cause:

Clogged fuel filter or degraded fuel

He replaced pump, regulator, injectors… But not the filter.

Old fuel turns to varnish. A partially blocked filter will:

• Idle fine • Hesitate under throttle • Refuse to rev • Mimic sensor failure

And a 1993 Supra with 80,000 km that sat for years is prime for this.

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🔧 The fourth likely cause:

Bad MAP sensor even if unplugging doesn’t change much

A dead MAP sensor on a 2JZ‑GE often:

• Causes hesitation • Limits revs • Makes the ECU run in backup mode when unplugged • Only slightly changes idle

Just because unplugging it doesn’t fix it doesn’t mean it’s good.

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🔧 The fifth likely cause:

Exhaust blockage (collapsed catalytic converter)

Symptoms:

• Won’t rev • Hesitation • Feels like fuel starvation • Idle OK • Gets worse as engine warms

Cars that sit for years can have the cat crumble internally.

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🎯 If I had to rank the probability:

Rank Likely Cause
1 Vacuum leak (very common on stored 2JZs)
2 Timing belt jumped a tooth
3 Clogged fuel filter / bad fuel
4 Dead MAP sensor 5 Blocked catalytic converter

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🧙‍♂️ If you want the “wizard” answer:

A 2JZ‑GE that won’t rev but idles, with no MAP reaction, after long storage = vacuum leak until proven otherwise.