How to KNOW if my TPS Sensor is Faulty?

1993 Nissan Quest

Engine doesnt start instantly when turning the key to "Start", it starts 2-3 seconds later.

The car idle speed surges (the needle vibrates mayb 50 rpms up and down...). You need to stare it closely to actually see it surge...I know surging is bad...it surges every 2-3 seconds.

I got my timing light and set timing to 15 degrees BTDC as tha manual says.

But, when it said to disconnect the TPS sensor connector (after engine is wamed and revd for 2min to 2,000rpm) when the engine is OFF....so I disconnected it, and started the engine, and it started instalntly!

Yet, the idle rpms werent as before (750 rpms approx), they were at 1,100-1,200 approx after the tps connector was disconnected....and the rpms werent surging, it was STEADY.

Does that mean the TPS is faulty?

The car idle speed surges (the needle vibrates mayb 50 rpms up and down...). You need to stare it closely to actually see it surge...I know surging is bad...

Things Ive replaced due to maintenance and worned stuff:

New Spark plugs

Plug wires

air filter

fuel filter

intake manifold and plenum gaskets

vacuum hoses

distributor cap and rotor

timing belt

o2 sensor

fuel hoses

coolant hoses

brake calipers

knock sensor

fuel injector o-rings

thermostat

coolant

IAC gasket / hoses

EGR valve cleaned and gasket

ATF fluid

I know many symptoms may be related to many faulty parts, but...during my test procedure....is that normal?

The 1,100 rpms....after disconnecting the TPS sensor and starting the engine?

1 Answer

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  • ?
    Lv 6
    6 years ago
    Favorite Answer

    On surging I would lean more towards the MAF/MAP sensor. You can try checking the TPS with a multimeter (if you have one analog type would be easiest) and watch the number change, the progression should be smooth and there should be no jumps or open circuit instances.

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