What would cause the engine to sputter when idling in gear with the ac on?

When the throttle position sensor (TPS) in a 4A30 engine Mini Pajero is not working properly, it can cause several issues. Some possible effects include:
1. Poor engine performance: The TPS provides feedback to the engine control unit (ECU) about the position of the throttle plate. If the TPS is faulty or not working, it may not accurately convey the throttle position information, resulting in incorrect fuel delivery and ignition timing. This can lead to sluggish acceleration, reduced power, and overall poor engine performance.
2. Unstable idle: The TPS plays a crucial role in maintaining a stable idle speed. If it fails, the ECU may not receive the correct signal indicating the throttle position at idle. This can cause the engine to idle erratically, with fluctuating RPMs or even stalling.
3. Transmission shifting issues: In vehicles with automatic transmissions, the TPS is also involved in determining when and how the transmission shifts gears. If the TPS is malfunctioning, it may provide inaccurate data to the ECU, leading to improper shifting patterns or hesitation during gear changes.
4. Check Engine Light (CEL): A faulty TPS can trigger the vehicle's onboard diagnostics system, causing the Check Engine Light to illuminate on the dashboard. This serves as an indicator that there is an issue with the TPS or its associated circuitry.
When experiencing any of these symptoms, it is advisable to have the TPS inspected and, if necessary, replaced by a qualified mechanic or technician familiar with the 4A30 engine in the Mini Pajero.

Were the Alternator & TPS Sensor tested & failed

Is that why they were replaced or just hung parts on
a wish & hope strategy?

Any Fault Codes present?

Road test with scan tool & review data: Fuel Pressure,Fuel Trim,
Oxygen Sensors,MAF Emission Monitors run clear?

Replace Spark Plugs every 3 years
Replace Front O2 Sensors at 100,000 miles
Clean MAF Sensor

Is there any type of idle control solenoid, that is not working
when the A/C is on?

A number of things could be the problem here:

1. Bad plugs - fouled plugs would cause erratic idling
2. Bad wires - also would cause erratic idling
3. Bad or worn distributor cap
4. Bad MAF (Mass Air Flow) sensor
5. Bad TPS (Throttle Position Sensor - this controls the idling speed under all conditions. A bad TPS would idle fine under certain conditions ie engine cold, engine warm with AC on etc but could be bad when truck is warm and at a stop.

Based on the information provided, it sounds like a bad TPS (Throttle Position Sensor). The TPS controls your idling speed under all conditions. When a TPS goes bad, you will usually notice the vehicle will idle when the engine is cold but once warm or with the AC on, it will sputter or stall.

The most common cause of your problem is the TPS. The Throttle Position Sensor regulates the idle under all conditions ie cold, warm, AC on. Unfortunately, it's electronic and can't be adjusted, only replaced. Another less likely cause is a loose or worn serpentine belt. This would prevent the alternator from properly replenishing power back to the battery. When the AC is on, it's a bigger draw than normal on your electrical system and could cause stalling. Although it's less likely, it's worth looking into prior to making a more expensive repair such as the TPS. Most chain auto parts stores and some service stations will do a free test on your charging system to ensure your problem isn't electrical.

sounds like needs a new fuel filter it is clogged

See if the idle control is working. I have a protegee that does the same thing, although the cause of mine is diffrent, it is the torque converter clutch not disengaging when stopped. Read the code, and see if there are any. Auto Zone will read it for free and give you a print out.

check for a defective PCV valve. cheap repair.

you could have a faulty Tps(throttle position sensor) this is located on the throttle body and has either a 4 wire plug or a 2 wire plug. I'm willing to bet that you need to replace this. the tps is responsible for your idle setting via the ecm(engine control moduel)...please rate this

Most sensors will trigger the check engine light, however the TPS(throttle position sensor) or EGR Valve(exhuast gas recirculation valve) could be potential causes. Does this problem only occur at idle? Is the idle normal in park? Let me know and I can try to assit further.

Hope this helps