i have a 98 4.0 auto, when i go to crank it up the first time after siitting it wont start, but when you let off and try and start the second time, it fires right up. once in a while on the first crank attempt it will start up but missing bad feels like running on 2 or 3 cyl, if you kill it then restart it runs fine.

any ideas would be appreciated.

it might need valve adjustment aswell, i can hear a small amount of valve chatter sometimes, my understanding is the valves are not adjustable manually in 4.0's? but forgive my ignorance if im wrong, i happen to be a toyota guy and not a big mechanic, i like suspension hahaha

 

crankshaft position sensor, or camshaft position sensor is what your starting issue sounds like to me.

as far as valve chatter, it's a bad lifter, bad/bent pushrod, rocker, or worn cam that is causing the chatter. this is not adjustable, only replaceable.


do us and yourself a favor and take the Fram oil filter off, and get rid of the Q-horsepower oil that's in it. this is just a guess as to what's in it...but in my experience 99.9% of the time, the valve chatter is direct result of some idiot trusting ****ty-*** filters and oil.

thicken it up by running a 10W rather than 15W, maybe even go up to 10W40 and see what she does.

 

I agree with this post, in fact I use Castrol GTX in mine, with a Purolator filter and have had no engine noise issues at all (same year Jeep, with 212K on the clock).

Starting issues on 'em can be caused by crank sensors, and the Neutral Safety Switch (NSS).

 

bad NSS would be no-crank or intermittent-crank issues...not starts second time around.

 

I always run 10w30 just got the jeep from a bud. changed the oil yesterday i just guess i havent driven it enough in the last two days for it to work itself out if its an oil issue and if its something else obviously wont go away in a few days.