Start then stall

[alexgalexg]

Hello everyone,
98 XJ AMC 242 4spd Auto 4x4

So i have had an evap code for large leak causing CEL. Was going to look into it next week but otherwise the jeep has run perfectly. No mpg loss or lethargic behavior of any kind.

Jump to today, walk out of a store and get in the jeep. I start it and it immediately stalls. Jeep runs fine but won't idle. Almost as if the IAC was not working. Here's the fun part, CEL light gone!

So I do the Sammy Hagar and one foot on the brake, one on the gas "hey!" my way home which was fine. Once I was in the driveway I had the guts to let off the throttle and now it idles on its own perfectly.

Just took it on the 15 min drive to work and it's still working perfectly fine and no CEL. Any thoughts? I'm baffled and don't want to throw an IAC or CPS at it just to throw something at it.

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[Tim_MN]

What Google symptom research and diagnostics have been performed ?

 

[8Mud]

The IAC gets gummed up and can be slow and/or iffy. The intake for the IAC is above the throttle plate in the TB the exit is below. If the IAC sticks shut as soon as you let your foot off the pedal the motor will die. I quick fix is to squirt some brake cleaner down the IAC intake with the engine running while you work the throttle by hand, this usually does the trick.
Might be you have vacuum in the gas tank, take the filler cap off and see if things get better. If it makes a big suck sound when you take the filler cap off you have likely found your issue, likely the purge solenoid.

 

[alexgalexg]

The IAC gets gummed up and can be slow and/or iffy. The intake for the IAC is above the throttle plate in the TB the exit is below. If the IAC sticks shut as soon as you let your foot off the pedal the motor will die. I quick fix is to squirt some brake cleaner down the IAC intake with the engine running while you work the throttle by hand, this usually does the trick.

Might be you have vacuum in the gas tank, take the filler cap off and see if things get better. If it makes a big suck sound when you take the filler cap off you have likely found your issue, likely the purge solenoid.

I did take the throttle body off, remove all the sensors and clean it well a few years ago. This was it's first cleaning and it was fairly clean already but ill try that regardless. It's running great now with no issues for the past 2 commutes, only happened that one time when the cel went away and no issue since. I'll check on that tank situation as well. It's going on a road trip tomorrow and I'll pop the live feed up for the trip, see if anything seems off.

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