My 4Y HiAce idles but the engine cuts out when I apply the slightest amount of acceleration. My thought is that the spark is not strong enough under load. Any ieas? Bruce

4y means 2004 year>? NO, no year told 4y is 1987 engine. carb
or 4yE, ecu EFI fuel injected engine 1997?????
NO CAR told at all , why skip that and sold to what COUNTRY?
the word is STALLS, means engine stop running and goes to 0 RPM/ stalls.
there are a huge lists of causes. and more tests.
it'll go off on it's own
means stall on it's own. use the word stalls, and it is way more clear.
engines are not light switches (on/off) so be clear.
fails hot or cold engine not told
my guess hot.(hot means normal temps.) if overheating many modern car (PCM brain) shuts off the engine to save it from damage. or drops cylinders like my 2004 chevy does.
I will make the the short list. (called a macro list)

1. engine bad, (ever tuned up ever (serviced) or cam belt slipped.
2. bad spark , top cause not turned up. means spark parts replaced and fall filters.
3. bad fueling, too much floods or too little fuel it starves and stalls.

there a bunch of tests, using skills and meters and tools to find the 3 causes. (a micro list I refuse to post here, a wall of endless text)

the answer is take it to a shop and get it fixed.
like 99. do today, most do. lacking tools or skills.

on big clue, is: for STALLS
IS
was the stall and instant and or violent stall? (spark common type)
or the stall was slow but smooth, stall. (fuel lost)
If I was driving I'd know that in seconds flat, and know what to do.

this is a USA answer and is not the 4YE answer.
4Y has a carb so carb is bad, too if spark and engine are ok.
like chock stuck on or carb float levels failing or carb needs full cleaning as most do and frequent. filters packed up>?

I'm Assuming that the engine is not misfiring but just a bog or a pause under acceleration. If so quite possible the TPS (throttle position sensor) is faulty. Then maybe airflow sender?

Some general thoughts - -
when you try to accelerate, a couple of things happen. The engine shifts sometimes, and you put it under a load unlike when it is idling.
Is it possible a wiring harness or a hose is moving when you accelerate ? Is it possible the fuel pressure or ignition module is not good enough to handle the engine under load ? Is the EGR opening early or something causing a vac leak and a lean fuel mixture ?

check fuel filter,air filter,spark plugs.

it could be a lot of things.. but if you smelled something burning then you may have already done damage to your car. id have it towed to a dealer.

Check the coil packs and EGR:
Exhaust Gas Recirculation System Operation Application of the Exhaust Gas Recirculation (EGR) gases is regulated by the Powertrain Control Module (PCM). It is based on engine coolant temperature, engine speed, vehicle speed, throttle angle and Manifold Absolute Pressure (MAP). The operation of the EGR system is monitored by the PCM, which allows gases to flow at a calculated rate and compares it against MAP sensor and oxygen sensor activity. The PCM anticipates an increase in MAP voltage and an increase in O2 sensor voltage.
Electrically operated vacuum control solenoids used to control the flow of vacuum to the EGR valve, rely on pulse-width duty cycle commands from the PCM to control its operation. Using input values and the operating conditions previously mentioned the PCM completes the electrical circuit for the solenoid to allow vacuum operation of the EGR.
In addition to solenoids controlling vacuum flow, the incorporation of a back pressure transducer regulates vacuum signals independently of electrical signals. When back pressure in the exhaust system is low, the transducer pintle is open and manifold vacuum is allowed to bleed off. As back pressure increases the amount of vacuum allowed to bleed off is reduced resulting in more vacuum being applied to the valve. This allows air pressure to open the valve.
The following symptoms can be caused by a faulty EGR valve due to loose connection, bad grounds, high resistance in the circuit, or opens in the circuit.
Related Symptoms

• Stalling on deceleration
• Stall at idle
• Surging off idle
• Unstable idle
• Running rough off idle
• Hesitation
• Stumble
• Chuggle
• Low idle
• Poor fuel economy
• Spark knock
• Stalling on acceleration

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coil packs:
Diagnosis and Testing Secondary Spark Test These spark tester looks just like a spark plug, attach the clip to ground and crank the engine to check for spark
This spark tester has an adjustable air-gap for measuring spark strength and testing different voltage ignition systems
Attach the clip to ground and crank the engine to check for spark
This spark tester is the easiest to use just place it on a plug wire and the spark voltage is detected and the bulb on the top will flash with each pulse
The best way to perform this procedure is to use a spark tester (available at most automotive parts stores). Three types of spark testers are commonly available. The Neon Bulb type is connected to the spark plug wire and flashes with each ignition pulse. The Air Gap type must be adjusted to the individual spark plug gap specified for the engine. The last type of spark plug tester looks like a spark plug with a grounding clip on the side, but there is no side electrode for the spark to jump to. The last two types of testers allows the user to not only detect the presence of spark, but also the intensity (orange/yellow is weak, blue is strong).

1. Disconnect a spark plug wire at the spark plug end.
2. Connect the plug wire to the spark tester and ground the tester to an appropriate location on the engine.
3. Crank the engine and check for spark at the tester.
4. If spark exists at the tester, the ignition system is functioning properly.
5. If spark does not exist at the spark plug wire, perform diagnosis of the ignition system using individual component diagnosis procedures.

Check the EGR Valve for stuck open condition with a vacuum pump.

If at idle you apply vacuum and it gets worse and shuts down or shutters, then that's not the problem. But, if you apply vacuum and there is a leak, there is a bad EGR valve on the car. If you apply vacuum and it operates the EGR and there is no change then the EGR should still be removed and the pintle cleaned, or a new EGR Valve should be installed.

Also, a coil pack could be causing this condition, where not enough spark gets to the spark plugs.

Is this a 4 tech or quad 4 engine?

Also, the cylinder head gasket could be burned through and allowing one cylinder to bleed exhaust to another cylinder on the Quad 4.

Good luck with this.

This can be your Idle control valve, when you turn the air on it puts the engine under load and your computer will increase the idle automatically to prevent the engine from cutting out.
When you are standing still and the car is shaking, by touching the accelerator very softly does the shaking stop? If so check the idle control valve.
I hope this will help.
Regards
Sam