The 2001 Jeep Cherokee uses a special design spark plug, which projects deeper into the motor than an ordinary plug. These plugs also are intended to be set at a smaller gap (.035") than most plugs these days. Many people do not know about this; and will either install a regular plug during a tune up, not check the gap, or set the gap too wide. That will cause hard starting. The correct spark plug for that motor is either a Champion #438 (RC12ECC), #4412 Truck Plug, #3034 Platinum Power, or #7034 Double Platinum Power. You can also use an Autolite #985, AP985, APP 985, or XP 985.
Another tip is that there are springs used to connect the ignition coils to the spark plugs; if any of these springs were left out when the new plugs were installed, it will cause hard starting and poor running. There are also rubber boots over the springs which attach to the plugs. These boots must be intact, and in good condition.
The battery cable clamps must be clean and tight. If they were not cleaned when the new battery was installed, I would definitely remove the clamps and clean them with a tapered reamer type battery clamp cleaning tool. I would also make sure the clamps are tightened to the point where they cannot be turned by hand. If they cannot be tightened that far, because the two halves strike each other; it may be necessary to remove some metal from between the two halves of the clamp with a hacksaw.
I would also get the alternator output checked, by connecting a digital voltmeter across the battery terminals. There should be at least 13.7 volts at the battery terminals when the engine is running. The voltage should not drop below that point when the lights and fan are turned on. If the voltage is lower than that, and the fan belt is not slipping; the alternator should be replaced.
Some low priced new batteries are undersized; and cannot supply enough power for starting in very cold weather. And, every so often, a new battery will be defective. Try getting the battery checked with a load tester. This is a specialized instrument which drains power from the battery and measures how much power the battery can supply without the voltage dropping too low. I would recommend that the battery should be able to supply AT LEAST 225 amps, while the voltage stays above 9 1/2 volts; for a full 15 seconds.
When you go to start the car, I would suggest turning the key to the position where the warning lights on the dashboard come on; and wait for a full ten seconds with the key in that position. Then turn the key the rest of the way to start the engine. That will allow enough time for the electric fuel pump to fully prime the fuel injectors. You also may find that the engine starts more easily when you either do not press on the accelerator; or just hold it down slightly.
I hope this helps!!!
Joel
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