Odd idle


#1

1988 Nissan truck with z2.4i 4 cyl and 5 speed.



My truck does not want to idle properly. On start up with temps below 50 it stalls at idle until warmed up, above 50 it doesnt stall but only runs at about 300 rpms. Once warmed up it will sometimes idle at about 900-1100 rpms and suddenly drop to 400 rpms for a few minutes. It will also sometimes stall when coming to a stop, whether the trucks warmed up or not. Heres a list of what I have done within the past 3 months, the problem existed before and after these things.



New plugs, wires, cap and rotor

New distributor

New O2 sensor

New fuel pump and fuel filter

New MAF sensor

Replaced all vacuum lines

Set timing and idle (did this when it

would idle)

Compression check (all cyl at 155-160)

Checked for leaks at intake and exhaust

manifolds

New PCV valve

New/Used throttle body (which replaced TPS,

injectors, mixture heater and

pressure regulator)



I did check for codes, it isn’t throwing any. Which doesn’t say too much on this engine it’s pre OBD so it isn’t too bright, their isn’t even a check engine light. Sorry for the length, but I figure too many details in this case is better than too few. Thank you for any help, this problem is driving me insane.


#2

Your vehicle does have a Check Engine light. So the bulb is probably burned out.

As to your problem, it might be with the Air By Pass/Idle Air Control motor. This came with the used throttle body you installed. So the original throttle body may have had a defective ABP/IAC motor. And the used throttle body may have a defective ABP/IAC motor.

Tester