Rough Idle When Cold Then Smooths Out. It could be either the vacuum leak or spark plugs that need to be replaced and looked at. No issues at start up or while accelerating.
One way to check for bad plug wires is to inspect the plug wire runs with the. This sounds like the idle may be staying to low at times if it smooths out with ac on, when the ac is turnned on the computer raises the idle a touch to make up for the strain on the engine from the ac compressor, clean throtlebody and look at and clean idle air control valve, if this valve is not controlling the idle when needed the engine will idle lower than normal and cause a rough idle. If too much air gets mixed in with the fuel, it will cause your engine to misfire.
Alternatively, You Could Get Lucky By Simply Having To Clean Your Fuel Injector Or Your Carburetor!
Engines need to run rich when cold, so the ecu dumps more fuel into the engine than is actually needed until it warms up, think of it as full choke when cold. If the egr valve is leaking, it will cause a rough idle, especially when the engine is warm. As the engine warms, it not longer needs the richer cold idle mixture and the engine runs smoother.if the car idles rough this can also be indicative of bad plug wires, distributor, or rotor.
After A Couple Minutes, I Can Drive The Truck On The Road And As The Engine Warms Up It Returns To The Nice Smooth Idle.
No trouble codes and the rough idle only lasted a few seconds. A stuck egr valve can cause a rough idle. Exhaust gas recirculation should only occur when the engine is at higher rpm.
Let It Cool Down For
One way to check for bad plug wires is to inspect the plug wire runs with the. It will run rough until the o2 sensors heat up and the pcm starts reading them. Then, using insulated plug wire pliers take out the wires from the plugged location.
As You Can See, There Are A Couple Of Things That Could Be At Fault When Your Car Starts Out Rough But Then Quickly Smoothens The Ride Out.
This also creates a vacuum within the intake manifold. Hook the other end of the tester to shop air to pressurize that cylinder. It could be either the vacuum leak or spark plugs that need to be replaced and looked at.
Bad Temperature Sensor (There May Be Several Temperature Sensors) Moisture Somewhere In Ignition System.
If you lower the idle, the choke on a cold day will keep the idle a little higher until the motor warms and then it will kick back off. No issues at start up or while accelerating. Based on my limited experience, common reasons for rough idle when cold include: