So the resurfaced/new v-seats heads are on.

[MarkJ]

Engine is purring like a kitten. Mechanic finds the oil pan almost rusted through. What is it with these weird Jeep problems? Oh well... add the new oil pan to the list.....

 

[RenKJ]

What did you get done on the engine exactly? Im guessing valve seats and something else, not positive

 

[MarkJ]

It was losing a small bit coolant through both heads. #2 and #4 on one side and #5 on the other. Getting intermittent missing on multi cylinders. It only happened on cold early morning starts. Otherwise ran like a top. Cooling system held pressure over night (witnessed by pressure in the tank when removing radiator cap). Decided to have the heads checked (no cracks), so they resurfaced them and replaced valve seats. Also having a catalyst and the muffler replaced. Oh, and now oil pan as well.

 

[MarkJ]

Turns out it may not need a new cat to fix the re-occurring (with increasingly shortening interval) P0420 code. The shop thinks the water going through the system may have thrown off the O-sensor. Every since the heads were fixed the code went away. Running like a top!

 

[twowings]

Excellent!

 

[LibertyTC]

Mark, How many miles were on the motor when these coolant problems developed?
Oil pans...ya tumors///oh Randy...!
Anyways, glad you are back with a decent engine again.:happy107:

 

[MarkJ]

About 176k

 

[MarkJ]

OK, I kinda fell off the Jeep online universe for over a year. Back now with additional important question... After we got the jeep back it seemed to run fine but within the week threw a Cyl2 mis code that will not go away. Also at this same time we were aware the idle started going low while at traffic lights, until it dropped enough that the oil pressure light would come on and the oil pressure beep would go off. I figured this was a function of the mis-caused rough idle. I changed that plug (because the shop ignored my plea to put standard copper cores back in (didn't help). I then swapped coils betwixt Cyl2 and Cyl4 and there was no change. Still Cyl2. Shop that did the work took it back and started the blame game. They changed the injector for Cyl2 - no change. They then started blaming the Cat on that side of the engine. Claimed it threw a code for the cat while they had it... I asked them why only Cyl2 was affected. No answer. I never saw the code and it was driven all last Summer with no cat code. In July we were going on vacation so I let the same shop have it for a week to troubleshoot further. They replaced the injector again and also replaced the oil sending unit because of the oil pressure light and beep. No change of course. They gave it back to me with the exact same symptoms and this time blamed it all on a (supposed) cyl2 leakdown issue. The compression on all 6 cylinders is in spec both for pressure and also for balance (all within same spec). They claim that just the leakdown is causing the mis on cyl2. I asked how that could be since the compression is fine and when running, the piston is moving fast enough leakdown (if true at all) doesn't even enter the picture...

So here I am with the same symptoms that started after we took delivery after they solved a coolant issue and found head gasket issues. They had the heads rebuilt and checked for cracks and flatness (by a 3rd party machine shop). They said that shop also checked all valve components before reassembling.

So why is it that through this cyl2 mis process they haven't checked their old work by even so much as removing a valve cover??? Could this be a bad valve seat, valve leakage or a lifter issue? When originally bringing it back I included a service bulletin from Jeep about valve train issues with this engine. They ignored it.

I think I am getting excuses and a run around because they don't want to pull a valve cover or head. They are using the leakdown test to point to a full rebuild or replacement that would then completely hide shoddy work on their part.

And yes, the reason I am putting up with all this is that the shop in question is owned be a friend who doesn't actually do the work. I have tried to be more than fair but am out of options. I am beginning to think I should have it checked by another shop without telling them any history and see where it leads?

The Jeep currently throws the CEL and Cyl2 almost immediately upon starting. The idle is rough and slows after you stop for a few seconds to chirp the oil pressure light most of the time (depending on how long you are stopped). Sidestepping the throttle obviously prevents this. It loses no coolant and runs at the correct operating temp even in hot weather with AC on.

Your thoughts are appreciated.

 

[ltd02]

I am beginning to think I should have it checked by another shop without telling them any history and see where it leads?

I'd vote for this. I know my vote isn't much help but this would be my next step. Maybe a fresh pair of eyes is all you need.

Any weird noises or anything? PCM? If it knocks enough at misfire the knock sensor will/should drop the idle to compensate.

Edit: Has your friends shop done any serious diagnostics on the electronics?

 

[LibertyTC]

A shop with a snap on ultra -live scanner/probe may be able to diagnose better and see misfire counts & data from injector & coil pack.
Having the correct NGK spark plugs gapped right is important too.
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Even tho the low idle may be a process of the knock sensor, have you replaced the IAC (intake air control)?
IAC went low at stops as well, cause port needed cleaning & IAC was a sticking-bad.
57602[/ATTACH]"]

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57604[/ATTACH]"]

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I also replaced the throttle position sensor as was erratic and worn.
57606[/ATTACH]"]

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[tjkj2002]

Bad cats can and will cause random multiple cylinder misfires but a constant #2 is a issue with #2 cylinder which the injector,plug,and coil has been eliminated.

2 things left....................

-bad head
-bad PCM

 

[MarkJ]

So does everyone agree that cyl leak down over night is silly as an excuse for cyl2 mis, as do I? When the compression on all cyl including #2 is fine?

 

[tjkj2002]

So does everyone agree that cyl leak down over night is silly as an excuse for cyl2 mis, as do I? When the compression on all cyl including #2 is fine?

None of the cylinders should hold any pressure once the engine if off.

Remember the rings have a cut in them,short term(real short) compression.

 

[belvedere]

The low oil pressure could affect a lifter, which could cause a misfire, but it's strange that it's always just cyl #2. I once had a Cherokee 4.0 that had a persistent misfire on cyl #1. After beating my head against the wall for a while, I swapped the valve springs on that cyl and that fixed it.

 

[MarkJ]

The low oil pressure could affect a lifter, which could cause a misfire, but it's strange that it's always just cyl #2. I once had a Cherokee 4.0 that had a persistent misfire on cyl #1. After beating my head against the wall for a while, I swapped the valve springs on that cyl and that fixed it.

Isn't there a tech bulletin about something like this? I found it and printed it out to give the shop on the first come-back but they ignored it.

Thanks
Mark

 

[belvedere]

Isn't there a tech bulletin about something like this? I found it and printed it out to give the shop on the first come-back but they ignored it.

There's a bulletin for certain years of the 4.0...not sure about the 3.7. I just mentioned it because any engine can have a weak spring.

 

[meoget]

Isn't there a tech bulletin about something like this? I found it and printed it out to give the shop on the first come-back but they ignored it.

Thanks
Mark

Check Engine Light/Misfire Due to Intake Valve Locks/Valves : Jeep Liberty Engine

Maybe?

 

[MarkJ]

Check Engine Light/Misfire Due to Intake Valve Locks/Valves : Jeep Liberty Engine

Maybe?

Thanks! That may be it!