Xj shutting down when at idle??

I have a 97 xj sport, 4.0L auto.

A few times when wheeling, the engine will stall at idle. The temp hand is at 100, the coolant is not boiling, yet it will not start as if its overheating. i wait 15 or 20 mins, it starts and runs fine. So tonight while doing some snow wheeling, it happened again. When i removed the rad cap, i herd a bubbling noise and the engine fired up right away!! Anyone have any idea what could be causing this problem?

Thanks

When you removed the radiator cap, was the engine hot ? Did any steam/boiling coolant come out ?

Are all your tune-up parts fresh ? Have you recently cleaned the Throttle Body and the Idle Air Controller ? How old is your battery ?

Newfoundland... Metric. 100C means it is running where it should (we call 210F) so the engine temp is most likey not an issue. Stalling at idle has a few usual culprits for you to check.

What sort of condition is the Throttle Body in? Full of carbon? If so, clean it paying particular interest in the Idle Air Controller passage. Personally, I prefer to use the remove/disassemble/clean/reassemble method rather than just pouring chemicals down it.

Your grounds could be less than ideal. Clean all of the grounding points.

IAC. The connector may have built up corrosion over the years and may need to be cleaned. Reseat it at the very least.

So, I am backing Tim_Mn up with the cleaning plus adding more cleaning. Tons of threads on how to get it done. I recommend cleaning the grounds (well, all electrical connections really) mechanically, not with chemicals that can migrate up the wire and lead to problems down the road.

Coolant was not hot, not boiling, no steam. Jeep is regularly maintained, battery is fresh. Thinking coil pack or crank positioning censor??

The next time it does not start, make sure you have an ohm/volt meter on hand, and start testing the grounds on the sensors, and testing the sensor readings one by one, with the meter and compare them to OEM FSM specs in the manual. When it is running, test the same sensors live, then look for what is way off spec. OHm tests must run with power and engine off. Live voltage readings can be taken with engine off, power on, or while the engine is running.

Check for fuel pressure at the fuel rail test location, and check for spark while cranking when it dies and does not restart.

Check the CPS signal (back probe the connector) while cranking under no start conditions!!!

It may be flooded, the engine. If it is, pushing the gas peddle to the floor while cranking will kill the fuel injector feeds until it unfloods!!!! If it starts, that is a clue it may be a leaking injector, or stuck IAC at idle starving it for air, that floods it.

Edit: Also get a code scanner, check for pending codes!!!

THE NEWF said:

Thinking coil pack or crank positioning censor??

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Think basic routine preventative maintenance and troubleshooting first. Clean the Throttle Body. The Idle Air Controller controls the engine idle, clean it. Clean wire connections, inspect for corroded wires or wire connectors. Test for proper voltage.

Test and inspect before you randomly replace parts in the hopes that you accidentally fix something.

I am also wondering what you heard bubbling, and why if you removed the radiator cap from a hot engine, nothing came out. Is your cooling system full of coolant, and free from blockage ?

I can't see any possible relationship here:

When i removed the rad cap, i herd a bubbling noise and the engine fired up right away!!

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I am not sure why he is messing with the cooling system anyway for died at idle and won't restart problem in the first place?

Is his gauge calibrated in degrees C?

Checked all electrical connections, throttle body gets cleanned every year. This is pretty much a trail rig and only see around 5000km a year tops, however it is used hard, so i am a little anal on maintiance. I've got a good running spare engine with all censors on it, so i may just swap them out and see what happens...Thanks for the advice!!!

Load test the battery if you get stuck. Newer batteries fail more than you think. Don't rule anything out.

One of the most common symptoms of a marginal battery is "stalling" at idle.

THE NEWF said:

I've got a good running spare engine with all censors on it, so i may just swap them out and see what happens...

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I sure hope your swapping sensors out, and not the engine, LOL!

Swapping sensors out will not locate a bad wire, or bad connector connection, or bad ground.