2000 GMC C2500 rough idle

RHUFF22

MEMBER
2000 GMC C2500
V8
4WD
AUTOMATIC
115,000 MILES

I recently changed the plugs and wires, replaced the fuel filter and the oil filter. After all of this was done my truck started idling rough but only does it after the motor heats up. It runs fine except when its idling. I used bosch double platinum plugs, auto lite wires, and a mobile one oil filter and oil. I have double checked all the plugs and wires and eliminated everything that I did while tuning it up. A friend of mine said it might be a sensor on the side of the intake but I just don't know. I just thought maybe you would have some ideas on what could have happened to make it idle this way.

1 Reply

PEAR69

MECHANIC
1,482 POSTS

This could be a few things, but first I must tell you about the plugs and wires you used. They simply stink. Bosch spark plugs should be taken off the market. I'm not sure about the auto lite wires either. If this problem started after you changed these items, I would at least change the plugs. The wires, being that I'm not sure about them, I would change too. A/C Delco plugs should always be used in these motors. Be sure the gap is set to spec. A/C Delco wires are expensive but they are properly designed for these high power ignition systems.
Is the check engine light on? Normaly, when any sensor is malfunctioning, the check engine light will come on. Do not go changing any sensors until you test them and determine that they are bad. Autozone or a place like that can and will test almost any sensor on your truck. Usually you can take it off and take it to them.
The sensor your friend speaks about just happens to be a sensor that, I believe, cannot be tested at autozone. It's the IAT (idle air temperature) sensor. This sensor adjusts the idle according to the air temperature by using a resistor that changes resistance according to the temperature. WOW sounds complex? It is just that, but it is easy to change. The coolant temperature sensor works the same way too.