99 XJ hard starting

Just bought a XJ about a month ago and having some problems starting when cold. I've read alot of the threads on many forum's but I want some opinions. It starts fine when I've drive it for awhile. But when it sits for alittle bit then it will crank and crank. I have to press the gas pedal all the way to the floor just to get it started. When it does start it runs like crap for a min or so, then it runs perfectly fine. Ok things that I've already replaced. I've replaced the TPS, Fuel check valve (fuel pressure reg), IAC valve, IAT (intake air temp), spark plugs, spark plug wires, & cap and rotor. I've cleaned the throttle body. I've also checked the fuel pressure, which is fine. I'm starting to think it's a Crankshaft position sensor or a bad ground somewhere. The battery and alternator is good. There is a check engine light. I scaned it with a Snap-On Solus and it comes up with a cylinder 5 misfire, which I think is cause by the rough ilde when it does decide to start. Any suggestions on what I should check or replace?

99XJPilot said:

..... I have to press the gas pedal all the way to the floor just to get it started. When it does start it runs like crap for a min or so ...

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For 1996+ Jeeps, the OBD-II engine computer (ECU/PCM) re-boots, and the idle settings are deleted, when you: (1) let the battery run down by leaving the lights or radio on, (2) disconnect the battery for an extended period of time, (3) when the battery goes bad and needs replacing, (4) when the alternator is not properly charging the battery, (5) or when poor battery connections result in a voltage drop at the PCM or poor battery charging. Loose, corroded, or damaged battery cables or ground wires may also cause or contribute to the problem.

Your symptoms are: (1) having difficulties starting the engine without depressing the gas pedal, and (2) the engine will have a low idle and probably stall unless you keep your foot on the gas pedal. (3) The ECU will relearn the idle settings after a short period of driving and the engine will start and idle normally.

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables or connectors and replace as needed. Copper wires should be copper color, not black or green. Do the same for the grounding wires from the starter to engine block, the ground wires at the coil, and the ground wires from the battery and engine to the Jeep's frame/body. You must remove, scrape, and clean until shiny, the cable/wire ends, and whatever they bolt to. Jeeps do not tolerate low voltage, bad connections, or poor grounds.

If the symptoms reoccur, you need to have your battery and/or the alternator load tested at a repair shop or auto parts store. This is usually a free service they offer to bring in potential customers. Even with low battery voltage, the engine will start, but the ECU can re-boot multiple times and a new battery may be required.

Cleaning the Idle Air Controller (IAC), regular tune-ups, and using fuel injector cleaner should be part of your routine preventative maintenance.

your symptoms resemble a leaking injector on cyl.5

pull the injector for 5 and swap it with one of the other ones, clear the code, and see if the misfire follows the injector.

First thing the computer looks at on cold start up is the ECT sensor. Check for a good signal with key on engine off and then again at first start up. That is what lets the computer know how much fuel to give at start up.