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Misfire on cold start and overheats?

Tiny
PCARPROBLEMS
  • MEMBER
  • 2022 JEEP GLADIATOR
  • 3.6L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 6,000 MILES
So, I have brought the vehicle in for service 5-6 times for the same issues. I am approaching a lemon.

Cold start cylinder 6 has anywhere from 20-700 misfires on initial start for about 30secs then it calms down and runs smooth. They did two software updates, changed valve lifters and some other parts on it with no luck ( I'll have to check the report). Got it back 2 weeks ago and it didn't misfire at all, but now that its back to colder temperatures here, it started again

The engine overheats usually while sitting still, goes up to about 230F hovers then goes up over 260F while driving. They replaced a valve they said was bad, but nothing changed, again its cold here and now its overheating, warmer days it didn't

Any help is appreciated.
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Wednesday, March 29th, 2023 AT 8:22 PM

8 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 43,639 POSTS
The first thing we should do is run the codes to see what comes up, which needs to be a CAN scan. You can get a CAN scanner (Controller Area Network) from Amazon.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

and

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Do you lose coolant over time? If so, it must have some defect in the engine or cylinder casting that allows the exhaust gases to enter the cooling system, also when the engine is running hot do you hear the cooling fan working? the engine should get louder when this happens.

Please check over this guide:

https://www.2carpros.com/articles/engine-overheating-or-running-hot

It would be good if we could remove the #6 spark plug to see what it looks like. Also, we can do a test to determine if exhaust gases are present in the system, please check out the guide below.

https://www.2carpros.com/articles/head-gasket-blown-test

Please go over these guides and report back.

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Thursday, March 30th, 2023 AT 11:29 AM
Tiny
PCARPROBLEMS
  • MEMBER
  • 5 POSTS
Thanks for the response, yes p0306 code, cylinder 6 misfire, My Jscan tells me on cold start the misfires in cylinder 6 are over 30+ one time 700+

yes, engine fan comes on about 225F

So, the dealer found a soft lifter spring on cylinder 6, replaced the whole even banks lifters, coil packs and spark plugs, they didn't note the conditions.

But

Started it this morning and my guess is the head gasket or cylinder went because all the coolant came out in a cloud of smoke that came out of exhaust, no coolant, over heating (obv), P0300 multi cylinder, parked it in driveway, getting it towed to dealer this week, last chance then I will lemon it.

So, the second time I brought it to the dealer I said it misfires on cold start cylinder 6, I said there is a compression issue either in the fuel line and/or cylinder, they blamed it on the lifters. I know little about engines and baffled they thought a cold start could be a lifter because the issue wasn't always present, I also suggested carbon build up being burned off after initial engine start, tell me I'm not crazy.

Any advice going forward would help, dealership isn't good at diagnosing this.

Probably fix head gasket, then they need to see the initial cause of the misfire.
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Thursday, March 30th, 2023 AT 8:29 PM
Tiny
PCARPROBLEMS
  • MEMBER
  • 5 POSTS
Hoping for a new engine, and when gasket blew the whole even bank was misfiring over 100+ each.
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Thursday, March 30th, 2023 AT 9:21 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 43,639 POSTS
Yep, it does sound like there is a flaw in the casting of the engine block or cylinder head. You might be on the right track with the lemon law, and you are not crazy, it sounds like they keep going around in circles, but the dealer may have it report to headquarters where they are told what to do. Please let me know.
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Friday, March 31st, 2023 AT 11:18 AM
Tiny
PCARPROBLEMS
  • MEMBER
  • 5 POSTS
Hey Ken,

They changed the cylinder head on cylinder 6, no more misfire on cold start but on a long trip (100 miles) I had 60 - 80 misfires on all cylinders except cylinder 1 which only had 1-2 misfires, no CEL came on, would misfires over longer trips be a concern? I bought an oil lab test that I will send out after I change the oil and wait a few 100 miles.

Thanks!
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Sunday, May 7th, 2023 AT 10:06 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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I would clear the codes and try again those misfire counts could be a result of the initial start-up when the cylinder head was replaced. Let me know please.
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Monday, May 8th, 2023 AT 5:39 PM
Tiny
PCARPROBLEMS
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No codes, my Jscan reads zero misfires on startup but then they slowly start piling up.
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Friday, May 12th, 2023 AT 12:10 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 43,639 POSTS
Can you confirm it only has 6,000 miles? If so, it sounds like you have a defective fuel pump, MAF sensor or PCM. Can you please post the codes? Also, was a CAN scan done or just a drivetrain scan?
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Saturday, May 13th, 2023 AT 9:57 AM

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