Trying to gather info to find commonality on "misfires"

[ShadowsPapa]

The tech diagnosed that coolant is getting in the combustion chamber. Rather than diagnose further and repair, the modern solution appears to be just throw it away and put in a new one.

It takes too much time and equipment for them to mess with rebuilds these days and no manufacturer is going to warrant a rebuild - too many variables, including techs that are clueless in engine builds/rebuilds.
Frankly, I'd not trust an engine rebuilt in a dealership these days.
We did it - well, I did it, but when I wasn't there the boss ordered reman short blocks or long blocks.
It takes a lot of hours to do it correctly and then if that one blows, and it's still under warranty- Jeep isn't going to stand behind something some guy with 6 months on the job did.

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[Jeepmonster]

My JT has been consuming coolant for some time. I have just over 28k miles, and I've had to add about 3/4 gallon since about 10 to 12k miles. I've always smelled something sweet, like burned coffee or maple syrup. The scent was most dominant at cold start up, then would dissipate. Scent was at the front part of the engine compartment (strongest near radiator). No scent anywhere else, like inside cabin or at tail pipe. No leaking coolant (at least visible) on the ground or engine compartment.

I used the engine block leak detector (like the one ShadowsPapa showed earlier), which showed combustion gas geting into the coolant. I pressure tested (only up to about 20 psi), and it held rock steady for quite some time (maybe about half hour). Did it hot and cold- no difference. Took it into the dealer, and they also checked for leaks and conducted a pressure test for a couple hours. They found nothing. They said the block leak detector is not reliable, as they have given false positives (not sure where else excessive CO2 can come from, other than a leaky EGR cooler).

Blackstone oil analysis (at 25k miles) showed high Potassium (1428) and "Pos" for anifreeze. I'll send off another sample before heading back to the dealer.

Last week, I got two consecutive days of P0300 (random multiple) and P0303 (cylinder 3) misfire codes at cold startup. If the light and chime didn't come on, I wouldn't have noticed. Still runs great.

 

[ShadowsPapa]

They said the block leak detector is not reliable, as they have given false positives (not sure where else excessive CO2 can come from, other than a leaky EGR cooler).

First I heard - we used to use that all the time and in each case, there was indeed an issue. It might not have been "easy to find" but eventually, we found it. Today - 'eventually' is just too far away for production shops.
Since there's very little air in that cooling system or reservoir, where can any errant gases come from?

 

[Jeepmonster]

First I heard - we used to use that all the time and in each case, there was indeed an issue. It might not have been "easy to find" but eventually, we found it. Today - 'eventually' is just too far away for production shops.
Since there's very little air in that cooling system or reservoir, where can any errant gases come from?

Agree, there's got to be a leak somewhere, especially now that I see high Potassium levels. Service advisor also said I have an "overly sensitive nose" because they could not smell anything.

I just wanted them to have it documented that I smelled and suspected coolant leak. They didn't find it strange that I had to add coolant occasionally. They said that is normal. I bought extended warranty just in case.

 

[Alpine Warthog]

Got a call back from the dealership. They confirmed a problem but think it's involving the egr valve or cooler or something....
They are keeping it another day and doing a leakdown test overnight

 

[Alpine Warthog]

Got a call back from the dealership. They confirmed a problem but think it's involving the egr valve or cooler or something....
They are keeping it another day and doing a leakdown test overnight

Leakdown test confirmed pressure loss. No oil in coolant or coolant in oil... Dealership is waiting for instructions from "STAR" (whatever that is)

 

[Lunentucker]

Leakdown test confirmed pressure loss. No oil in coolant or coolant in oil... Dealership is waiting for instructions from "STAR" (whatever that is)

STAR is when the local tech gets on the phone with a higher level tech and they work on it together.

 

[ShadowsPapa]

Leakdown test confirmed pressure loss. No oil in coolant or coolant in oil... Dealership is waiting for instructions from "STAR" (whatever that is)

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[Alpine Warthog]

STAR finally got back and said to replace the egr cooler. Getting covered by the 70/7 emissions warranty...
GONNA TAKE A WEEK TO GET HERE geez.

 

[Jeepmonster]

I took my JT into the dealer today for the following issues: P0300 (random misfire), P0303 (cylinder 3 misfire), coolant in oil, "disappearing" coolant, and radiator leak (coolant steam came out of front grille area).

What finally prompted me to set up an appointment was what appeared to be a radiator leak. Here is a picture of what it looked like while I was parked on the side of the street.

I drove home immediately. There was a bit of wetness on the transmission cooler (in front of the radiator), but just a faint bit of steam coming out near the middle (not by any hose clamps). waited till things cooled down for a couple hours and started back up. No leak. Drove it for a week until my appointment today. No visible decline in coolant level in the reservoir.

A few days after the radiator leak, the engine light cleared on its own, but I figured the code would be stored. It had previously had the two misfire codes stored. I knew the aux battery was going bad. ESS disabled and charging voltage was always pegged (14.4 volts). I replaced it. The main crank battery was replaced about six months ago. Charging voltage was back down to about 12.7 volts while driving around. ESS worked as normal.

Described everything to the service advisor, who plugged in their scanner. Guess what, no stored codes! She said misfires can occur due to either battery going bad. If bad batteries were the cause of misfires, she said it is likely the stored codes were cleared on its own (after a few run cycles) once I replaced the aux battery. Looking back, that makes sense. The check engine light used to come on shortly after start up on cold mornings, when batteries had drained down overnight.

They will diagnose the rest of the coolant related issues (radiator leak, coolant in oil). Here is the potassium level from the analysis. I left them a copy of the oil analysis.

Now, the wait...

 

[ShadowsPapa]

A few days after the radiator leak, the engine light cleared on its own, but I figured the code would be stored. It had previously had the two misfire codes stored. I knew the aux battery was going bad. ESS disabled and charging voltage was always pegged (14.4 volts). I replaced it. The main crank battery was replaced about six months ago. Charging voltage was back down to about 12.7 volts while driving around. ESS worked as normal.

Described everything to the service advisor, who plugged in their scanner. Guess what, no stored codes! She said misfires can occur due to either battery going bad. If bad batteries were the cause of misfires, she said it is likely the stored codes were cleared on its own (after a few run cycles) once I replaced the aux battery. Looking back, that makes sense. The check engine light used to come on shortly after start up on cold mornings, when batteries had drained down overnight.

14.4 isn't "pegged" - mine runs upper 14s, even 15 if it's cold out, and normally is in the 14s since I don't drive it enough to keep the batteries up. So unless you drive that thing daily and longer trips, being in the 14s isn't a sign of a bad battery by itself.

The 12.7 you are seeing means only that at this time, the batteries are fully charged (assuming the batteries were both charged and the IBS reset when you replaced the battery back then)

I'd be really surprised if the bad battery caused misfires - when it's running and charging at 14.4 volts, that's what's available since the batteries are connected in parallel, and the alternator is actually also in parallel with the batteries, meaning any of them, and all of them are sitting with that voltage at the posts.

 

[Jeepmonster]

Got a call from the service advisor. Head gasket (not surprised). They did get a P0303 code while troubleshooting and determined that it was caused by coolant seeping into the cyclinder (maybe others, as I've gotten P0300). Warranty will cover everything, including the diagnoistics (over $500) and rental car. They will still look into the radiator while it is in the shop. Some closure at least.

 

[ShadowsPapa]

Got a call from the service advisor. Head gasket (not surprised). They did get a P0303 code while troubleshooting and determined that it was caused by coolant seeping into the cyclinder (maybe others, as I've gotten P0300). Warranty will cover everything, including the diagnoistics (over $500) and rental car. They will still look into the radiator while it is in the shop. Some closure at least.

There's a positive in this as well - they'll have that bank apart, head, etc. and see the cams and followers and hopefully will take a close look to make sure they look like they should - no scoring and so on.

For some reason - not real surprised to see this outcome.

 

[Jeepmonster]

There's a positive in this as well - they'll have that bank apart, head, etc. and see the cams and followers and hopefully will take a close look to make sure they look like they should - no scoring and so on.

For some reason - not real surprised to see this outcome.

Yes, somewhat relieved that they found the culprit (at least A culprit). I'm kind of disappointed with the last dealership who said there was nothing wrong and that I have an overly sensitive nose. I almost want to go back to say "I told you so." I hope they look at the other components, as you mentioned. Ironic that I went to this dealership based on the previous one who had such a backlog (couldn't take me in until mid April).

 

[Hootbro]

Got a call from the service advisor. Head gasket (not surprised). They did get a P0303 code while troubleshooting and determined that it was caused by coolant seeping into the cyclinder (maybe others, as I've gotten P0300). Warranty will cover everything, including the diagnoistics (over $500) and rental car. They will still look into the radiator while it is in the shop. Some closure at least.

How was the Aluminum, Copper, Lead and Tin numbers on your oil analysis? That is usually where long term coolant contamination starts to degrade the crank bearing material.

Like @ShadowsPapa mentioned, hopefully the check everything out on the heads and also do a straight edge check of the block and heads before slapping another head gasket and send it.

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