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Pentastar Misfire on Cylinders 1, 3, & 5


Threepointsix

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Update - Leak-down came in with less then 1% loss - so no problems there. Got PCM from flashmasters, same cyl1 and Cyl2 misfire at idle only. I have no idea what else could possibly cause this. SO, decided to bite the bullet and take it to a "highly rated" dealer, Garavel Jeep in Westport CT with issue quickly going from $165 diagnostic to $500 with no answers as of yet. Will update if dealer is able to solve the issue

This is for damn sure a mystery that I'm eagerly awaiting to see resolved. Fingers crossed they find it. Curious, though.....if they continue to diagnose it into the 1k price, will you just give up or have them throw a new engine in it?

Me, I'd try to negotiate absorbing some of the cost of diagnosis into that new engine.
 

BLACKJKU

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This is for damn sure a mystery that I'm eagerly awaiting to see resolved. Fingers crossed they find it. Curious, though.....if they continue to diagnose it into the 1k price, will you just give up or have them throw a new engine in it?

Me, I'd try to negotiate absorbing some of the cost of diagnosis into that new engine. But thats me.

Yea but what if it turns out to be a electrical problem and a new engine is installed and problem is still there?
 

Rdartua

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Well, I really cant imagine what the new engine would cost coming from dealer - I think its cheaper to just trade it in for another car. On top of it - as blackjku said - what if its not new engine? - So far mechanically engine passes all of the tests...
 
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Rdartua

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Yea but what if it turns out to be a electrical problem and a new engine is installed and problem is still there?
HI, I have seen you all over this forum, specifically commenting on misfires - which apparently plagues pentastar engine. Whats more - for the most part all of the posts on misfires end up open ended - meaning no solution. Have you seen anyone actually resolve this mystery issue?
 

BLACKJKU

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HI, I have seen you all over this forum, specifically commenting on misfires - which apparently plagues pentastar engine. Whats more - for the most part all of the posts on misfires end up open ended - meaning no solution. Have you seen anyone actually resolve this mystery issue?

Not to many, some if they did fix it were so happy they forgot to let us know what fixed it. I just did remember something that was causing a problem on some of the years, something about the way a harness was routed and causing problems on the right side of the engine.

It's not just the Jeeps either it's all Chrysler made vehicles, there are electrical problems with all of them. I'm on a Dodge Diesel Forum and the newer trucks are always having electrical issues. This is the main reason why I say if I start having issues that can't be fixed easy or cheaply it's getting a user friendly engine.
 

Rdartua

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Ill tell you one thing, this is my first experience with Chrysler products and only because my 16yo talked me into it.
Coming from GM v8s - super easy and reliable engines and Honda/Toyota v8s and v6s - I am thoroughly disgusted with Chrysler. People really should read the forums before buying these things. The design and complexity of the engine, terrible wiring looms - literally kept together with sparse electrical tape, plastic intakes, oil housings, constant electrical issues, tipms failing, engine compartment cramped and overheated with all that plastic. I am shocked, but mighty jeep is a disposable vehicle. Sure - lets throw hemi, new trans and all gearing with upgraded ball joints and u joints - then it will be heck of a car. Oh wait - but the electronics are still crap.. I honestly thought they would stand by their Jeep product, but its completely other way around. There is really zero support from even highly rated dealers - first thing they ask - how many miles on the car - you say 111k, and the response is: oh boy..
So definitely a disposable vehicle, will probably end up trading it in for 4runner - something that lasts.
 

Threepointsix

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@Rdartua that's you're best move. Im looking at used Tacomas and Tundras. Even with 85k mileage and up, they're much more reliable than the JK platform.

I mention the 'new' engine, even though I do believe it's an electrical issue, because Ive heard of dealers quick to suggest a replacement before actually finding or fully diagnosing the issue. A new engine is surely a costly 6k and up. So yeah, you're probably best to trade it if they can't figure it out.
 
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Creston

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An engine is easy to diagnose. Its all mechanical. If the leakdown, compression, and visual checks of the engine are good then swapping another good engine will fix nothing.

The electrical/sensor/ computer side is likely the issue and will be kept. An engine that is bad/low compression etc etc won't run fine on one startup and miss the second one.

And yes Mopar as a company has been so plagued by reliability issues that is has been bought and sold repeatedly for 20 years. NO other car company has been sold repeatedly in their 100+ year history. Much less multiple times in 20 years. I bought 2 brand new in a week back in 08. I will Never buy another Mopar made after about 1975 or so. I do however work on them a lot in my shop and still have my Rubicon. Once its dead (and its well on its way to rotting apart with only 54k miles) ill never have another. Toyota, Ford, GM, etc etc have occasional hiccups too but just look at the 80s,90s,00s models with 300-400k on them compared to Mopar with the same.

When I bought my Rubicon in 08 I debated between an FJ and the Jeep. Made the dumbest choice possible. Have regretted it greatly since. I wanted to "buy American". Jeep has been German, Italian, half French, and Dutch since then....
 

Rdartua

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At this point it has been 3 days at the dealer and they cant figure out the issue. It started as $165 and now up to $500 as of now for diagnosing the issue. Honestly, I am not sure its worth it fixing it, I think I am better off just trading it in for Toyota, problem is - god damn engine light. Which only misfires at idle. Its so unpredictable - usually these engines would show issues under load not at idle. Has to be valve train issue, I would think computer or electrical would show up across the range of rpm...
 
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Threepointsix

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At this point it has been 3 days at the dealer and they cant figure out the issue. It started as $165 and now up to $500 as of now for diagnosing the issue. Honestly, I am not sure its worth it fixing it, I think I am better off just trading it in for Toyota, problem is - god damn engine light. Which only misfires at idle. Its so unpredictable - usually these engines would show issues under load not at idle. Has to be valve train issue, I would think computer or electrical would show up across the range of rpm...
Already heard it from two mechanics local to me who've said the same thing: "the weakness of these Jeeps in the valve train" and, "I get these all the time."
 
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Creston

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At this point it has been 3 days at the dealer and they cant figure out the issue. It started as $165 and now up to $500 as of now for diagnosing the issue. Honestly, I am not sure its worth it fixing it, I think I am better off just trading it in for Toyota, problem is - god damn engine light. Which only misfires at idle. Its so unpredictable - usually these engines would show issues under load not at idle. Has to be valve train issue, I would think computer or electrical would show up across the range of rpm...
Not necessarily. Plenty often the electrical issues are only at idle. How is the battery and the alternator output BTW. With the valve coversoff and a visual, combined with leakdown and compression checks you can tell any valve train issues. Plus any valve timing issues will have a code (cam/crank correlation/ phasers etc etc etc codes). Plus a mechanical valve train issue won't go away for a startup cycle then come back on the second run.
At least in my experience. Based on what I've read about your case. I'd bet electrical. And I work on them every day.

I have a dodge I do oil changes and routine service on (customer says its his last dodge too. Life long dodge man in his 60s). It came up with a cyl 8 (and sometimes a few others) misfire at idle. Started years ago. He has put 150k on it since it developed and nothing has changed. Sharp Hemi truck too.. So there is always that option unless you live in a state that won't allow driving with the check engine light on.
 
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Rdartua

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I dont think engine light is an issue, considering that it runs perfect on road, my question will it pass emissions with misfire?
 

Creston

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Already heard it from two mechanics local to me who've said the same thing: "the weakness of these Jeeps in the valve train" and, "I get these all the time."

Yeah. And I use internet research and experience a lot too. But people also get into "ive seen it 100 times" and don't properly diagnose. If a subaru comes in amd the heater is blowing cold or antifreeze is low they start pulling a head for a head gasket. And yeah there is a 90% chance thats it. But still have to look at clues and diagnose. A Dealership should be able to diagnose it pretty easily regardless. They have specialized tools just for that make that those of us with shops don't have. The fact that Jeep has been owned and swapped by so many companies and engines and such likely doesn't help getting one properly fixed. Which factory trained tech do you need for your model... Daimler Benz, Fiat Chrysler, Stellantis.... I think that's a lot of the "bad Mopar service department" problem.

If a late 90s early 00s ford truck has electrical issues people automatically assume GEM module (similar to TIPM) because they did go bad. Especially with a truck with clearance lights. They leaked water down onto the GEM. I saw one guy change three because of a couple issues he had. Window not working light flickering and heater blower dead. I told him it wasn't his GEM. Blower motor is independent of the GEM. He wouldn't listen. Eventually I changed his window switch, interior light bulb and the resistor on his blower motor. After several hundred dollars in gem modules (and a lot of standing on his head to change it lol) he was fixed for 50 bucks

Another one this week was a tri-axle I had that the owner had watched a few youtube video and diagnosed his turn switch. I changed it. No fix. Then his module...again no fix. 500 dollars spent because of internet "its usually this" videos. They are only a starting point. And very helpful at that.



Common issues are a good starting point but people make the mistakes of throwing the parts that the internet said to throw.

Just this week in my shop I had a 100k mile jeep wrangler that had a P0128 code. Internet said temp sensor and thermostat. Owner bought both. No diagnosis at all. Temp sensor was fine.

Valve train issues (the mechanical part) do not intermittently cause issues. If you can clear the code and it is fine for one drive, you aren't actually fixing anything mechanical yet its ok. Id look toward what you are changing wuth clearing the code which is the computer/learned values/ electrical portion.

When you see a list of parts and "still not fixed" then people aren't diagnosing. They are just doing what someone else did.

And I have commercial accounts at the box parts stores. I'm telling you that every part you pulled and changed with those parts that was still good..... you put on a very inferior part.

As far as emissions that was my point. On many states there is no inspection. In some there is no emissions, only safety. My state is actually split. Half has emissions half has only safety.

Even more stupid than that is a vehicle 30 years old or older is exempt....so your 2021 Ferrari has to come to us to check your headlights and such... but your 1980s chevette or cressida is deemed "safe" by the state. Lol
 
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Threepointsix

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One thing I can say in response to the following comment:

"Just this week in my shop I had a 100k mile jeep wrangler that had a P0128 code. Internet said temp sensor and thermostat. Owner bought both. No diagnosis at all. Temp sensor was fine."

Im going to guess that it's cheaper to change both the temp sensor and thermostat after reading a code than it is to take it to a shop and have them professionally diagnose AND fixed it. But then again, if it isn't DIY resolved its still a trip to the shop + repair + what you did = extra cost 😂
 

Creston

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One thing I can say in response to the following comment:

"Just this week in my shop I had a 100k mile jeep wrangler that had a P0128 code. Internet said temp sensor and thermostat. Owner bought both. No diagnosis at all. Temp sensor was fine."

Im going to guess that it's cheaper to change both the temp sensor and thermostat after reading a code than it is to take it to a shop and have them professionally diagnose AND fixed it. But then again, if it isn't DIY resolved its still a trip to the shop + repair + what you did = extra cost 😂
Id guess autozone or one of those guys did the original scan for free. To properly diagnose you would only have to watch the live data for 3 minutes. Lol. Jscan would be fine for that.

My point is that I'd have pulled a higher quality brass temp sensor to install an off brand inferior plastic one. Not that anything on a Mopar is "high quality"... but their sensors are better than the store brand ones .
 
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Threepointsix

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I keep reading and seeing this "Jscan" all too often on the forums and even have a friend who has it (if I recall correctly, installed?) in his JT.

Is this a universal thing that I can buy for my JK? In other words, is there a specific type of Jscan, for example: Jscan plus, or Jscan XLT2 or 2.0 etc, or is it a one model type thing?

EDIT: don't know why I bothered asking when I could simply Google 😵‍💫 Which I just did.

I buzzed my friend who has it, so I can get some insight. I remember him saying he had a shop "install it". But I also know he's not the type to do anything DIY.....which is why I thought it was something that needs installation. Looks like its plug, select and play.
 
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Creston

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I keep reading and seeing this "Jscan" all too often on the forums and even have a friend who has it (if I recall correctly, installed?) in his JT.

Is this a universal thing that I can buy for my JK? In other words, is there a specific type of Jscan, for example: Jscan plus, or Jscan XLT2 or 2.0 etc, or is it a one model type thing?

EDIT: don't know why I bothered asking when I could simply Google 😵‍💫 Which I just did.

I buzzed my friend who has it, so I can get some insight. I remember him saying he had a shop "install it". But I also know he's not the type to do anything DIY.....which is why I thought it was something that needs installation. Looks like its plug, select and play.
Yeah. Most jeep guys use it. I don't personally. I have dedicated scan tools myself since I work on all make. Diagnosing your problem would be a hell of an endeavor im afraid. Actually having the correct live data or getting a freeze frame at the correct time is going to be rough. Somewhere a sensor should drop out or something though. I just dont see how a mechanical issue could go away for one start cycle.

I would have thought a dealer would have no issue finding the problem though. The 3.8 and the 4.0 were bare bones simple engines. The 3.6 is a good deal harder to deal with but it's still not a very complicated engine. A far cry from the new V8s with variable valve timing, start/stop and cylinder deactivation or from the newer turbos.
 

Rdartua

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Yeah. Most jeep guys use it. I don't personally. I have dedicated scan tools myself since I work on all make. Diagnosing your problem would be a hell of an endeavor im afraid. Actually having the correct live data or getting a freeze frame at the correct time is going to be rough. Somewhere a sensor should drop out or something though. I just dont see how a mechanical issue could go away for one start cycle.

I would have thought a dealer would have no issue finding the problem though. The 3.8 and the 4.0 were bare bones simple engines. The 3.6 is a good deal harder to deal with but it's still not a very complicated engine. A far cry from the new V8s with variable valve timing, start/stop and cylinder deactivation or from the newer turbos.
Wait - I did not say it was one stop issue. It keeps misfiring Cyl 1 and 2 at idle all the time. As soon as I raise idle speed top say 850 misfire goes away. Btw - I am one of those guy who either replaced parts with OEM mopar or superior. - NGK spark, MSD Coils, upgraded Oil filter housing - oem new from 2017, all sensors either oem or bosch, or NTK - which actually make for Mopar. So inferior quality is certainly not an issue. Plus I threw parts at is as also part of 100k maintenance. Live data and freeze frame I am running off WiTech software using high end MichroPod clone which runs wiTech perfectly.

So as you can see I am b***ls deep into the issue. That being said Jeep has been sitting at dealership since Friday with no resolution, they called me to say they want to keep longer, I said as long as you need - so maybe another week. It has their tech stumped and I think he is taking it personally ;-) - like I did. Will see what pans out.

BUT - why i suspected valve train - is potentially low idle rocker wobble? Couldn't be oil actuators? What would cause misfire on low RPM - what actually happens at low speed? Wiring I eliminated by tracing back to PCM, PCM I swapped same issue - so I have trouble believing its electric.

Btw - below is another thread dealing with the same issue with no resolve.:

 

Rdartua

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And remember its only Cyl 1 and 2 which are opposite banks - so that really should rule out fuel rail since cyl 2 is right at the feed, BUT both cylinders are closes to oil actuators...what else?