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the 4.0L engine?
is this engine cold or hot.
why is 2000 rpm wrong for 60mph., (depends on engine and axle size and what gear you were in , then)
the idle speed for hot is too high
did you scan the PCM yet?
if hot , idle is high, is the thermostat holding water temp 180f or above. ? if not that is the problem.
you don't adjust the idle for any accessories
The idle is set for smooth running of the engine( normally 750-900 rpms with a drop of 200-300 rpms with an ac running so set the idle at the upper rpms and it will still be smooth when the ac is on without affecting gear engagement
your problem I take it is that when the ac cuts in the idle rpms drops and makes the engine run rough
This is normal as the ac compressor takes up to 5 hp to drive it
what you need is an electric controlled vacuum pot connected to the accelerator lever so that when you switch on the ac the power to the ac clutch energizes the pot and vacuum pulls the accelerator lever to maintain the set idle rpms
such an item is found on most early carby operated engines
If it was doing it when cold I'd say definitely, but your problem is when warm right? Maybe throttle position sensor? The ICV is pretty expensive ($85 and up). Just to take it our of the equation maybe clean it. I've never done mine, but Googling it, it doesn't look overly hard. Hopefully you have a garage or better weather than I'm having today!!. Good luck. Hey, when you figure it out come back and let us know what it was.
Hi Dave the ECU receives messages from sensors, one of which is a temperature sensor. When the sensor responds to a temp higher than the normal operating temp the fans are then and only then supposed to operate. They will switch in for a brief period and then turn off again. The idle speed is in direct relation to the cold start up idle requirements and specifications. When the engine is cold the idle speed will automatically increase and as the engine achieves operating temp, the idle speed will decrease inthe way you have recorded. If you start the engine and allow it to idle until normal temp is achieved the fan should cut in. The way you've desribed all systems are A okay!. Regards John
it will have codes but the scanner in use doesn't have the right protocol for reading them
Indicates a faulty ambient air temp or BARO sensor so there will be codes
a coolant tempurature sensor will make it run to rich if it is bad. run rough at idle, and produce black smoke, engine may stall out. it also causes retarded timing, slow idle speed, cold hesitation or stumble, poor fuel milage. good-luck!! if light is on check for problem code. this will guide you in the right direction. if no scanner, any auto parts store will scan for free. repost if need be. have a good day!!
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