Could The Timing Be The Problem??
02-12-2021, 03:29 PM
#16
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Location: VA
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Year: 1998
Model: Cherokee (XJ)
Engine: 4.0
Do you know what your coolant temp is when the jeep is cold, like in the morning..it should closely match the iat..The hotter it is, the leaner the mix. If thats incorrect then it might overly lean out making tough to start. If it starts good on the 2nd or third attempt you may have a fuel pump or check valve problem where it takes a while to prime. What is your fuel pressure at start and while running . At highway speeds my ign advance runs in the mid 30's. As far as I know spark timing is set by the crank sensor in the bellhousing and cam timing sets injector stuff. Supposedly none of that is directly controlled by you even if you misalign something. Is yours an original motor The flexplates might be incompatible if ever changed.. sorry my data collection methods aren't as cool as yours
The fuel pump is only 2 yrs old and this is the original motor. I'm in the process of learning "diagnostic language" so please bare with me. I bought the scanner because I hate giving up trying to fix something and I hate bringing it to a mechanic even more!
One thing I found that I don't like is when I tested the harness for the TPS, I'm getting 4.72v from the middle pin and 5.17v on the outer PIN with just the ignition on. I also added in a ground from the harness to the firewall so the ground is good.
02-12-2021, 07:44 PM
#17
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I have not tested those wires so I can't give you good info. Basic premise....mechanical things don't fix themselves by turning off and then back on...only elec stuff does that...not a whole lot of help but it narrows the possiblities...just keeps you from running down a rabbit hole
02-12-2021, 08:03 PM
#18
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Year: 1998
Model: Cherokee (XJ)
Engine: 4.0
I have not tested those wires so I can't give you good info. Basic premise....mechanical things don't fix themselves by turning off and then back on...only elec stuff does that...not a whole lot of help but it narrows the possiblities...just keeps you from running down a rabbit hole
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