Engine thumping noise

[Matthewmcox]

So I just picked up a 2019 Jeep rubicon 2.0t less than a month ago and I’ve noticed that on a cold start, it’s making a weird thumping noise from the intake tube…

There Is no cel and it drives fine once it’s on the road…this doesn’t seem normal, wondering if I need to take it in or start looking at lemon laws

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[DaltonGang]

Could be some backfire. Definitely take it in, and have them keep it, so they can start it on a cold morning.

 

[Carolina Jeeper]

A sticky valve can do that. If an intake valve doesn't fully seat, the combustion pressure can come back through the intake manifold.

Or the ignition system is somehow causing a spark at the incorrect timing. If a coil pack is intermittently working it's very possible that's the source. Coils send out the spark when they de-energize since the magnetic field is collapsing and this creates the voltage spike. No matter the cause of a coil pack de-energizing it sends out a voltage spike every time.

 

[mwilk012]

If it is easily reproducible, it should be simple enough to check for backfiring. Live scan data of intake pressure and check for spikes. Otherwise, something’s loose.

 

[Mtrad003]

Sound like this? 17 seconds in. Happened at 10k miles. Dealer replaced plugs and did some other magic and it went away. Now back again at 20k. Service has had it 3x, can't figure out and nothing strange on scan, so they are going to chase timing chain gremlins this week.

 

[avidangler]

Reviving an old thread, any resolution to the thumping? My jeep recently started making this noise.

 

[Matthewmcox]

Nothing… it still does it, but only when it is below freezing.

 

[mwilk012]

Sound like this? 17 seconds in. Happened at 10k miles. Dealer replaced plugs and did some other magic and it went away. Now back again at 20k. Service has had it 3x, can't figure out and nothing strange on scan, so they are going to chase timing chain gremlins this week.

Good lord that sounds terrible.

 

[DaltonGang]

Nothing… it still does it, but only when it is below freezing.

Well, did you ever take it in to get it looked at???

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