Would you say its A or B?

[Toploader]

Ok off we go
1986 5.0 GM..........when cold car idles rough...a real rock and roll affair............till it heats up..........then...........smooth as a babies ass..............so I need opinions please............do I replace the Engine Coolent Temperture Sensor (A) or take off the Idle Air Control(B) and spray a cleaner in it.

Thanks in advance

[1990LTD]

Probably the coolant sensor. Testing is easy but they're like 10 bucks..if it's old I'd replace it anyway and see what happens.

[gadget73]

do both, but its probably one of the temperature sensors. There are 2. One is the coolant temp sensor, the other is the air temp sensor. Air temp is on the driver's side, just behind #5 injector, coolant temp is in the pipe on the passenger side, just forward of the edge of the upper intake manifold. A code scan may tell you which is bad.

[Toploader]

I forgot one thing!.............maybe an intake manifold leak?..............I have to take some brake cleaner spray and hit the area around the runners...........just one more thing to eliminate!

[gadget73]

If the idle isn't high, its probably not an intake leak. These idle really high with vacuum leaks. If you have original vac lines though, change them since a leak on the MAP sensor line will make it run like poo.