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1999 Jeep Grand Cherokee sputtered after tuneup

Took my 1999 jeep grand cherokee laredo to get a tune up and oil change, when I was driving today the day after I had it done, when I was going slow or stopped it would sputter really bad and almost stall out. What could it be?

“Tune-up” is a vague word. Please list the services that were done.

You have checked the oil level, I hope.

They changed the spark plugs and no I didn’t check the oil level. Will do that.

I’m seeing conflicting info for the 6 banger 4L. Not sure it has distributor or not. I presume it is coil on plugs, with waste spark design, no distributor. Here’s some ideas

  • Changing the spark plugs somehow damaged the wires or coils.

  • Ignition timing has somehow been changed.

  • This engine I believe used an idle air control motor to control idle rpm. Maybe that went bad at the same time the plugs were changed. Or maybe the tune-up involved that area (throttle body area) of the motor and somehow adversely affected the idle speed. There’s an idle rpm screw on that engine that is never supposed to be adjusted. All idle control functions are done by the IAC and the PCM. If the tech changed the position of that screw, that is likely the problem.

Suggest to ask shop to check the idle rpm at various coolant temperatures and the idle ignition timing.