4.0 Starting hard when warm

skyhighZJ

skyhighZJ

Gov retirement < needs to live
Joined
May 31, 2012
Location
Aberdeen, NC.
I have a 97 XJ 4.0 aw4 and when cold it starts right off the bat but when the engine has any heat in it from running and I try to start it it takes several cranks then almost sputters to a start. It's not showing any codes or engine light. Any thoughts?
 
You are encountering heat soak. All of the heat from the exhaust header is soaking into you intake manifold and messing with the throttle body sensor. You have a few options for this. Insulate your intake so it does't get baked. Instal a timer for your electric fan for when you turn your jeep off which will keep the temps down. Cut vents into your hood. Just search on the web for heat soak issues for a jeep cherokee xj or any 4.0
 
looked it up and the only related sensor is the TPS (Throttle Position Sensor) is this the one you are talking of? I already have hood vents and a temp controlled fan that runs after shut down for approximately a minute. Guess I will change it out and see if it remedies the issue. Thanks Oleblue.
 
It could be heat soak as stated above. 2000 and 2001 XJs as well as WJs were notorious for that.

You also could have an injector leaking down. Install a fuel pressure gauge, start it up and then watch the gauge after you shut it off. See how quickly and to what degree the pressure drops. You can also unbolt the fuel rail (engine cold) but leave the line hooked up. Cycle the key a few times to build pressure. Observe the outlet side of the injectors to see if there is any dribble of fuel leaking out.
 
when its hot, if not fixed yet, cycle the key 3-4 times and see if it starts right up. if it does, bad fuel pump/regulator(all one unit) if it doesn't, could be coolant sensor in T-stat housing or pull the coil out and make sure its not cracked on the back side real bad(also very common on jeep coils) hope this helps.
 
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