"Dead" cylinder with compression??

[Vgirl]

Hi, hoping someone can shed light on this.

I'm being told one cylinder is dead in my 3.7L v6. But it has 140 psi of compression. I'm not a mechanic nor engineer. I'm not an idiot either so common sense would lead me to believe dead cylinder = 0 psi. When I asked the mechanic, "how does a dead cylinder give compression?" he said that is what he couldn't figure out.

How is this possible? And what could be causing it? Is it a telling symptom of something specific?

Any thoughts are appreciated.
Thank you!!

 

[ElCheapo]

What do you consider a "dead" cylinder?
Typically, that would be one without ignition (spark). So, is there good spark?
It could have good compression with a stuck valve, are the valves working properly? Broken rockers happen on the V6's.
You might need a better mechanic.

 

[Vgirl]

What do you consider a "dead" cylinder?
Typically, that would be one without ignition (spark). So, is there good spark?
It could have good compression with a stuck valve, are the valves working properly? Broken rockers happen on the V6's.
You might need a better mechanic.

Thank you, ElCheapo.

I consider a "dead" cylinder as non-functional in some critical way. I've no clue what the mechanic considers it as.

Unsure if it has spark. I was told injectors, coils, and plugs plus pcv valve and breather hoses were replaced. "Runs better than it did but no change in the cylinder." Haven't been told anything about valves or rockers. (In reading thru the forums for days now, I understand Jeep plugs should be copper NPK?? Unsure if the mechanic used those or not and if not, if that would make a difference in spark?)

I've also learned here about rockers, lifters, cam, and valve seat drops (altho that one would give 0 or low compression). However the mechanic has not mentioned anything about rockers or valves (besides pcv valve).

Thank you again, and please let me know if the above makes more (or less) sense.

 

[Billwill]

Needs copper NGK plugs but that should not cause a completely dead cylinder.

Could be a bad coil pack....swap the bad cylinder coil pack over with a different one.

Could be a bad injector...check the connectors to that injector is on tight.

With battery disconnected re-plug the connectors on the PCM a few times in case you have a dirty connection.

You should get a better mechanic and may have to inspect the valves and lifters on the bad bank.

Do you have any CEL codes posted?

 

[Vgirl]

Thank you, BillWill. My dad's name was Bill. He had an old CJ he loved. I guess love for my KJ is in my DNA.

Copper NGK plugs. Sorry! I garden and apparently my mind remembered it as NPK (used in fertilizer).

Okay, I was told:

- Coils were replaced (I assume that means coil pack?).

- Injectors were replaced.

- The PCM connection test was mentioned as a hail mary but not tried because of a reason I can't recall. Sorry, the past 2+ weeks of dealing with all this has melted my mind some. But I remember, "that wouldn't work on yours because of" something.

- CEL was "throwing cat codes" but cats were fine upon visual with a scope. They were not removed and inspected. I wasn't given the CEL code numbers. Once I get my KJ towed out I will check via dash/odo scan.

A bit more info that might be helpful:
-The o2 sensors were replaced 4 mos ago. I was told they are now dirty. But CEL o2 sensor codes were not mentioned.

-Oil changes religiously. Small leak in the rear main so I've been checking and adding high-mileage oil regularly between changes for the past 2-3 yrs. It was advised by this mechanic that I do that rather than have the rear main seal repaired. At time of break down it was 2.5 qts low which was very unusual for its regular small leak related consumption.

I've been watching a YouTube video series by Astral Auto Repairs of a partial rebuild on an 03 KJ 3.7L to learn more about and what could be wrong with my engine. The episode I just finished covered examining valves and lifters. So I now have a better idea of what you mean. Still unsure what is wrong with mine. But I am learning in the process and everyone's replies help so much. Any other thoughts you may have are very much appreciated!!

Thank you!

 

[JasonJ]

Even with an oil leak, it is not likely that only one cylinder would experience oil starvation and prematurely wear out the compression rings... I'd expect that to be nearly all or all cylinders.

140psi is low(er) pressure than typical, but the lowest cylinder should be within 10% of the highest and all would be considered "normal". I don't recall what normal psi is for the 3.7 pentastar. I'd expect upwards of 180.. so something specific to that one weak cylinder (I wouldn't call it dead, I'd call it weak) is going on.

A sticking valve makes sense... allowing some cylinder compression to escape during the combustion cycle.

Did your mech say if he performed the compression test wet, dry, or both? Hint: He should have done it dry first, then wet- meaning adding some oil to each cylinder to see if the reading changed and by how much.

If this is the same mech that gave you misinformation about the A/C compressor, then I third the comment that you need someone better, with more skill.

 

[ElCheapo]

Since the injectors and coils were already replaced, try switching them around, to see if the "dead" issue moves to another cylinder. That would indicate whether new coil or injector is good. It is possible for new parts to be bad.
If bad, get replacements, hopefully problem solved.
If not, then the valve covers need to come off to check valve operation.

If throwing codes, and O2 sensor already dirty, it sounds like you are getting fuel, it is just not burning in the cylinder, which should be spark related.
It could also be wiring for the injector.

 

[towpro]

this may sound far fetched, but I got stumped once and old guy working for me solved it.

car had miss, like dead cylinder, worse at higher RPM.
Scope on ignition all looked good (back when you could use an O scope on cars).
Compression tested good,
Did not have OBD back than.

turned out it had a broken valve spring. It would hold valve well enough at low RPM for compression test, but running valve would bounce causing miss.

 

[Vgirl]

Guys, THANK YOU SO MUCH!!

JasonJ: Agreed. Again, I'm not a mechanic but common sense = a leak as primary cause would affect all cylinders, not just one. I only mentioned it in relation to knowing the 2.5 qts low was very unusual, because I've been adding oil for past few years and know its related consumption rate.

I appreciate your term of weak cylinder vs dead. And yes, a sticking valve makes sense from what I've learned. I was not told whether compression test was done dry, wet, or both. But I've learned about those here and on jeepforum from my searches.

Yes. This mechanic was the 3rd to give the A/C misinfo. First opinion was by a kid who worked at a Chrysler dealership who was a friend of an acquaintance, in process of getting his ASE, had a lift in his parent's garage, and charged me $100 cash to do the serpentine belt (which I bought separately at autozone) bypass in his driveway that took 20 mins. The 2nd misinfo on A/C was from the shop I was working with prior to this current shop. So 3 mechanics, 2 shops, and 3 summers of sweating until I could get it repaired. This current shop is who did the entire unit replacement.

ElCheapo: Yes, I was told coils and injectors were swapped in the way you described and didn't make a difference. Sorry, I should have mentioned that in my other post.

Okay, that makes sense, it's getting fuel just not sparking. Injector wiring! That wasn't mentioned by this mechanic as a possibility but makes sense as a possibility. I'll keep that in mind and learn more about it. Agreed about valve cover and inspection. I've been learning about that and what to look for. I'm not afraid to turn wrenches and look at or do something myself if I can. I used to hold the drop light or flashlight for my dad when I was little while he worked on his CJ and other family vehicles. And I'd always ask him, "What's that? What does it do?" I used to change my own oil until convenience outweighed time factor.

towpro: Not far fetched at all! Because from what I've learned and understand now, the spring is what closes the valve, right? So if the valve is stuck open, it could be that the spring is non-functional hence keeping it open providing good compression, but in a stuck way. Am I following that correctly?

I saw a post the other day and took notes, so I know better what you mean:
Camshaft lifts lifters
Lifters push pushrod
Pushrod pushes rocker
Rocker pushes valve open
Spring closes valve

I am so very grateful for all of you guys taking the time to help me out. It means so much:flowers2:

 

[ElCheapo]

If the valve is stuck open, it will release compression, and/or hit the piston. If the rocker malfunctions the valve will not open, and you will have compression.

I don't think your problem is the spring, that wouldn't cause a dead cylinder. It seems like it is either spark or, it is in the valve train. Could even be a collapsed lifter.

 

[Vgirl]

Thank you, ElCheapo.

What if an injector (or spring) fails? Would either one cause fuel to fill the cylinder or related area and have compression from that?

Or, if a rocker malfunctions, would it affect the injector's function at all? And/or would the injector still attempt to fill the cylinder area with fuel but get no spark?

Would a collapsed lifter cause a knocking sound? Or would that be from the pushrod against a bearing?

Thank you again for your help!! And for your patience while I learn and ask all these questions.

 

[Billwill]

Try get us some codes pulled from the PCM....may point us to a misfire and point us in the right direction.

 

[JasonJ]

towpro: Not far fetched at all! Because from what I've learned and understand now, the spring is what closes the valve, right? So if the valve is stuck open, it could be that the spring is non-functional hence keeping it open providing good compression, but in a stuck way. Am I following that correctly?

I saw a post the other day and took notes, so I know better what you mean:
Camshaft lifts lifters
Lifters push pushrod
Pushrod pushes rocker
Rocker pushes valve open
Spring closes valve

I am so very grateful for all of you guys taking the time to help me out. It means so much:flowers2:

Yes, you have that process correct- although not all engines use pushrods (anymore). Some engines are designed such that the camshaft actuates directly on the lifter. Most lifters are hydraulic in that they have an internal spring and plunger design that fills with oil and is "pumped up" by oil pressure.. others are solid or "flat tappet" designs that are just machines tubes of metal. If a hydraulic lifter fails, it can be for a number of reasons, but even just low engine oil resulting in low oil pressure can collapse a hydraulic lifter and cause a misfire or cause the valve for that lifter (or lifters) to not open or close properly.

Thank you, ElCheapo.

What if an injector (or spring) fails? Would either one cause fuel to fill the cylinder or related area and have compression from that?

Or, if a rocker malfunctions, would it affect the injector's function at all? And/or would the injector still attempt to fill the cylinder area with fuel but get no spark?

Would a collapsed lifter cause a knocking sound? Or would that be from the pushrod against a bearing?

Thank you again for your help!! And for your patience while I learn and ask all these questions.

If an injector fails, it simply stops spraying fuel into the cylinder. If all other things are working normally, this causes a dry misfire. The cylinder still makes compression, the spark event still fires off.. just there is nothing to ignite so you lose power and have a dead miss in that cyl.

Fuel wont fill the cylinder unless the valves stop opening, the injector continues to spray, the spark plug stops firing, and eventually (not long, like seconds later) the amount of fuel in the cylinder will increase the compression of the cylinder so much- because remember, it can't pump the air inside out, because valves are stuck shut for some reason and liquid doesn't compress like air does- that the compression will be too high for the design of the parts and you'll break something catastrophically. Hole in the piston, broken connecting rod, hole out the side of the block level stuff.

If a rocker (or valve spring/lifter) malfs, it will not affect the injector- normally. Now we get into camshaft position sensors and PCM functions. The camshaft position sensor tells the computer where each valve is in the cycle, open or closed and sometimes by how much. It uses that information to know when to fire the injector, and sometimes for how long. Some vehicles fire injectors one at a time along with the 4-cycle process, this is what you've probably heard or seen as "sequential fuel-injection". Others fire the injectors in pairs or some other combination, these are "batch-fired fuel injection" systems. They waste more fuel and are not used much anymore because it is inefficient.

But normally, in the way that you are thinking, a malf'd rocker or spring is not going to make the injector stop firing.

A collapsed lifter will cause a sound. Usually a loud and very noticeable TICK, plus the sound of the misfire itself, which admittedly sometimes sounds like a knock. Pushrod against a bearing-? I don't follow.. if an engine uses pushrods (ours do not), the pushrods ride on top of the lifters and then gets seated at the top under a small round depression in the rocker arm itself. Engine oil provides the "bearing surface". But this does not apply to the 3.7L Pentastar v6.

Good luck hunting this down. If it were mine, I'd re-do the compression test and see what numbers you get.. being sure to perform it dry first, then again wet. See how and if the numbers change. If you can confirm that you have one specific cylinder with low(er) compression, that gives you something to focus your attention to. If the wet compression test numbers are same or similar for that cylinder.. that would indicate to met hat the cylinder rings are not the issue, and that something else is causing a leak of compression in that cyl. Like a valve spring that won't seat and close fully..

In that case, hope for a busted valve spring or collapsed lifter. If the valve seat broke... eek. I've seen that destroy cylinder heads (Some Ford 4 cylinders I've owned were notorious for that).

 

[ElCheapo]

What Jason said.
The only thing I would add is to check the spark plug for operation. There is a possibility that the wiring to that cylinder coil is faulty, although that should throw a code.

I forgot that those motors are overhead cam and do not have lifters.

 

[JasonJ]

What Jason said.
The only thing I would add is to check the spark plug for operation. There is a possibility that the wiring to that cylinder coil is faulty, although that should throw a code.

I forgot that those motors are overhead cam and do not have lifters.

Right, and since I'm regurgitating information today...

That means that instead of the camshaft lobes pushing up on the lifter and in turn moving the rocker arm on a pivot, with the spring to push the other side and close it.. the camshaft lobes push DOWN onto the lifters- or hydraulic buckets of a sort, and those act on the valve stem directly. This is more efficient because you aren't changing direction a couple times, down is down, not up then down. Smoother, different power band than In-block camshafts.

 

[tjkj2002]

- CEL was "throwing cat codes" but cats were fine upon visual with a scope. They were not removed and inspected. I wasn't given the CEL code numbers. Once I get my KJ towed out I will check via dash/odo scan.

A bit more info that might be helpful:
-The o2 sensors were replaced 4 mos ago. I was told they are now dirty. But CEL o2 sensor codes were not mentioned.

#1-I've had several dozen 3.7/4.7's with bad cats that caused misfires even when all cylinders properly worked and had good compression.You can not "visually" inspect cats for proper operation,they work or they don't.

#2- if the O2 sensors where not NTK or at least Denso O2 sensors you will need to replace them again,this engine(and all Chrysler's) do not like Bosch O2 sensors.

 

[Vgirl]

If an injector fails, it simply stops spraying fuel into the cylinder. If all other things are working normally, this causes a dry misfire. The cylinder still makes compression, the spark event still fires off.. just there is nothing to ignite so you lose power and have a dead miss in that cyl.

Fuel wont fill the cylinder unless the valves stop opening, the injector continues to spray, the spark plug stops firing, and eventually (not long, like seconds later) the amount of fuel in the cylinder will increase the compression of the cylinder so much- because remember, it can't pump the air inside out, because valves are stuck shut for some reason and liquid doesn't compress like air does- that the compression will be too high for the design of the parts and you'll break something catastrophically. Hole in the piston, broken connecting rod, hole out the side of the block level stuff.

If a rocker (or valve spring/lifter) malfs, it will not affect the injector- normally. Now we get into camshaft position sensors and PCM functions. The camshaft position sensor tells the computer where each valve is in the cycle, open or closed and sometimes by how much. It uses that information to know when to fire the injector, and sometimes for how long. Some vehicles fire injectors one at a time along with the 4-cycle process, this is what you've probably heard or seen as "sequential fuel-injection". Others fire the injectors in pairs or some other combination, these are "batch-fired fuel injection" systems. They waste more fuel and are not used much anymore because it is inefficient.

But normally, in the way that you are thinking, a malf'd rocker or spring is not going to make the injector stop firing.

A collapsed lifter will cause a sound. Usually a loud and very noticeable TICK, plus the sound of the misfire itself, which admittedly sometimes sounds like a knock. Pushrod against a bearing-? I don't follow.. if an engine uses pushrods (ours do not), the pushrods ride on top of the lifters and then gets seated at the top under a small round depression in the rocker arm itself. Engine oil provides the "bearing surface". But this does not apply to the 3.7L Pentastar v6.

Good luck hunting this down. If it were mine, I'd re-do the compression test and see what numbers you get.. being sure to perform it dry first, then again wet. See how and if the numbers change. If you can confirm that you have one specific cylinder with low(er) compression, that gives you something to focus your attention to. If the wet compression test numbers are same or similar for that cylinder.. that would indicate to met hat the cylinder rings are not the issue, and that something else is causing a leak of compression in that cyl. Like a valve spring that won't seat and close fully..

In that case, hope for a busted valve spring or collapsed lifter. If the valve seat broke... eek. I've seen that destroy cylinder heads (Some Ford 4 cylinders I've owned were notorious for that).

What Jason said.
The only thing I would add is to check the spark plug for operation. There is a possibility that the wiring to that cylinder coil is faulty, although that should throw a code.

I forgot that those motors are overhead cam and do not have lifters.

Right, and since I'm regurgitating information today...

That means that instead of the camshaft lobes pushing up on the lifter and in turn moving the rocker arm on a pivot, with the spring to push the other side and close it.. the camshaft lobes push DOWN onto the lifters- or hydraulic buckets of a sort, and those act on the valve stem directly. This is more efficient because you aren't changing direction a couple times, down is down, not up then down. Smoother, different power band than In-block camshafts.

#1-I've had several dozen 3.7/4.7's with bad cats that caused misfires even when all cylinders properly worked and had good compression.You can not "visually" inspect cats for proper operation,they work or they don't.

#2- if the O2 sensors where not NTK or at least Denso O2 sensors you will need to replace them again,this engine(and all Chrysler's) do not like Bosch O2 sensors.

Thank you SO much, JasonJ, ElCheapo, and tjkj2002!! This is super helpful, guys. Learning so much. I'm definitely deep into the rabbit hole now haha.

It wasn't until last week that I learned what I was told by the shop was all based on speculation, nothing was actually looked at beyond external. I'm not sure the valve cover was even removed. (Because a simple compression test is done with it on, right?) So, I wanted to wait until I had it towed out from there before replying to everyone.

What they "thought what was going on" was that 1) the fuel injector failed and stayed open, causing fuel to build up on top of that cylinder, creating a vapor lock. And that then 2) a rod bent or got tweaked and is now up against a bearing. (I may have confused connecting rod against bearing with pushrod against bearing in my other post.) That what they think happened happens in 5% of vehicles and race cars all the time. The theory about mine was based on the mechanic's track camaro that had a carb failure dump fuel onto cyl.

And from what you're saying, JasonJ, injector failure as a primary cause of fuel build up wouldn't be possible. That in that case it'd be a valve issue, correct?

I was able to pull codes from the dash. P0201 and P0302. The cat codes might have been cleared. What I learned about P0201 goes back to what you said, ELCheapo, about the injector wiring. All I could find from searches was about the 4.0 I-6 tho, but that the harness can rub against a stud/bolt and cause these two codes, short circuits, plus the symptoms I had at breakdown. I'm not sure if ours have the same harness and stud/bolt location design, but it's def worth considering. Either way, def looking at the wiring in general. And also the PCM issue as another possibility like Billwill mentioned a few posts ago.

As for the cats, tjkj2002, I was told by that shop the cats "looked fine." And that a scope was used to see them, altho the front or top maybe(?) isn't visible with the scope. I didn't know that doesn't mean anything until your post, so thank you. I also learned from searches since that bad cats can cause sounds, too, is that correct? The cats are original on mine. Yes, thanks, that shop probably put in Bosch o2 sensors. I'll have the sensors changed to the ones our engines like.

I appreciate all the advice and honesty and will get a second opinion for sure.

Oh, and I saw from the PCV thread here that the 02-06 OE design is weak. The PCV valve and breather hoses were cracked on mine according to that shop. So if cracks happened, that makes me think pressure built. If pressure built, there could be a clog. And a clogged PCV could cause a valve to stick, right? So there's another possibility, maybe?

Through all this and everyone's help, I'm seriously considering getting tools and doing what work I can do myself. This forum is so inspirational that way. All of you have been a huge reason I haven't given up, despite that shop adding $1K to the estimate per conversation about a reman r&r, pushing a junkyard motor swap, and telling me to just get something else.

So, thank you everyone!!

 

[JasonJ]

Thank you SO much, JasonJ, ElCheapo, and tjkj2002!! This is super helpful, guys. Learning so much. I'm definitely deep into the rabbit hole now haha.

It wasn't until last week that I learned what I was told by the shop was all based on speculation, nothing was actually looked at beyond external. I'm not sure the valve cover was even removed. (Because a simple compression test is done with it on, right?) So, I wanted to wait until I had it towed out from there before replying to everyone.

What they "thought what was going on" was that 1) the fuel injector failed and stayed open, causing fuel to build up on top of that cylinder, creating a vapor lock. And that then 2) a rod bent or got tweaked and is now up against a bearing. (I may have confused connecting rod against bearing with pushrod against bearing in my other post.) That what they think happened happens in 5% of vehicles and race cars all the time. The theory about mine was based on the mechanic's track camaro that had a carb failure dump fuel onto cyl.

And from what you're saying, JasonJ, injector failure as a primary cause of fuel build up wouldn't be possible. That in that case it'd be a valve issue, correct?

I was able to pull codes from the dash. P0201 and P0302. The cat codes might have been cleared. What I learned about P0201 goes back to what you said, ELCheapo, about the injector wiring. All I could find from searches was about the 4.0 I-6 tho, but that the harness can rub against a stud/bolt and cause these two codes, short circuits, plus the symptoms I had at breakdown. I'm not sure if ours have the same harness and stud/bolt location design, but it's def worth considering. Either way, def looking at the wiring in general. And also the PCM issue as another possibility like Billwill mentioned a few posts ago.

As for the cats, tjkj2002, I was told by that shop the cats "looked fine." And that a scope was used to see them, altho the front or top maybe(?) isn't visible with the scope. I didn't know that doesn't mean anything until your post, so thank you. I also learned from searches since that bad cats can cause sounds, too, is that correct? The cats are original on mine. Yes, thanks, that shop probably put in Bosch o2 sensors. I'll have the sensors changed to the ones our engines like.

I appreciate all the advice and honesty and will get a second opinion for sure.

Oh, and I saw from the PCV thread here that the 02-06 OE design is weak. The PCV valve and breather hoses were cracked on mine according to that shop. So if cracks happened, that makes me think pressure built. If pressure built, there could be a clog. And a clogged PCV could cause a valve to stick, right? So there's another possibility, maybe?

Through all this and everyone's help, I'm seriously considering getting tools and doing what work I can do myself. This forum is so inspirational that way. All of you have been a huge reason I haven't given up, despite that shop adding $1K to the estimate per conversation about a reman r&r, pushing a junkyard motor swap, and telling me to just get something else.

So, thank you everyone!!

Speculation.. so they guessed without actually testing anything beyond the compression test that was done (and probably done incorrectly). That's the same as the advice you're likely to get from the parts monkeys behind the counter at a local retail parts store (Of whom I used to be).

So if an injector stuck open and dumped fuel into the cylinder, it'd cause a dead miss for sure, but that fuel would get pushed via exhaust stroke out the exhaust valve.. and into the exhaust. It may ignite during that time and that would be a backfire that you'd hear for sure. That could damage the cat converters, or at least cause a fault code to set. On the compression stroke it could cause damage, but that leads me to...

I guess as to whether a stuck injector could cause vapor lock on the engine would be dependant on exactly how much fuel went in when it first happened, how much could be expelled via the exhaust stroke the next time up the cylinder and then the rate of filling vs the rate of exhausting.. it's possible...not sure how likely. Like, I really don't know the percentage.

P0201 is an injector circuit malfunction.. that could the issue altogether, or that could be a cause for an injector to remain open, spraying fuel. Depending on what the circuit fault is, usually a short to ground, it's either going to cause the injector to fail and stop, or open when it shouldn't. Needs more diagnosis.

P0302 as you probably know is a cylinder 2 misfire detected.. so so many reasons why that could pop up.

I'm wonder if the shop, when saying they "looked at the cats with a scope", mean that they didn't do a visual inspection, but rather "checked them out" via a digital oscilloscope... used to see the wave function output of the sensors. They could be using generic terms that are misinterpreted as physically LOOKING at them with an optical scope.. instead of "testing" them with a digital 'scope (note the apostrophe... taking the place of "oscillo-").

I still think you need a more competent shop to look at this... if this one can't be bothered to go into DETAIL on why you have a multi-thousand dollar quote in front of you, and just expects you'll say OK and just go with it, then they are of questionable quality in my mind.

If I'm going to quote someone the amount of used vehicle purchase and expect them to pay it, I'm going to take the time to be thorough and explain it to their satisfaction.

 

[Vgirl]

Yep. Speculation. No wonder the mechanic looked guilty, nervous, and all squirrely when I went in to pay and asked him to tell me again what he found. Funny you say it's the same as a retail parts store advice. That mechanic told me recently he wants to have his shop become like a regular "pep boys." Well, he's on track for that. But lost a customer for sure.

Oh, and apparently speculation, a fuel injector, + a few ignition parts = $590. Let's just say I'm a zen master for not jumping across the counter. Btw, this issue began 3 wks ago. I've been without my Jeep all this time plus incurred rental car charges and a ton of stress. Valuable time and money that could have been spent at a competent shop. Instead I was ****** around by this shop and their questionable service.

Okay, so I smelled strong odor of raw fuel at time of breakdown. It happened after I stopped, checked/filled oil, and restarted. It seemed like it was coming from under the raised hood but I can't say for sure. It may have been coming from the exhaust, I don't know. I was in the drivers seat, door open, when I smelled it. A man and his son who stopped to help were up front outside. They smelled it too. I didn't want to push the issue by running the engine so I just shut it off quickly and called for the tow at that point. Definitely did not hear a backfire tho.

I asked that very question about the fuel injector dumping fuel and causing vapor lock. Like, how quickly can it happen. Because I drove my KJ cold and only 2.8 miles before the issue began. My Jeep has never overheated, at least according to the temp gauge (which I've since learned sometimes doesn't mean much). I was told: "You never know. It can spew a lot of fuel in a very short time." This confused me because it's not like I drove it, limped it, or ignored it. I pulled over right away and stopped. Idk, maybe it's an unknown stat in general.

When it happened, the best way I can describe the symptoms are like when a vehicle is out of fuel. I've never done it myself but have been in vehicles when that's happened. It started shaking and kinda choking like it was struggling for fuel. Stalled, too. I did have to restart it for a few seconds to get off the road. So that + smell of raw fuel made me first think fuel system issue. I've not had the fuel pump replaced. A friend thought maybe a clogged fuel filter. Idk if the codes it pulled would be caused by those tho.

Yeah, you're likely right about the wording of the cat scope terms and I took it as literally looking with a scope that shows a better view visually. I know the cats can be partially viewed from underneath, so I misunderstood. Thank you for clearing that up!! So, in that case the cats "tested" fine.

Yes, yes. I will have a second opinion for sure, hopefully soon. And you're right. The kind of behavior from the now former shop. The pricey speculative diagnosis, the multi-thousand estimate that grew each jasper reman conversation, the insistence on getting a different used vehicle or junkyard engine. Telling me there's "definitely something internal going on" but that I could drive it 12 miles home. Definitely questionable quality. And perhaps, greed and/or laziness. TBH. I knew I was done with that shop 2.5 wks ago when he suggested to me, a manual trans Jeep girl, that I get a Honda CRV. Super insulting.

Moving forward. The new shop I spoke with is highly recommended and knew what I was talking about when I shared the things I've learned here. So that was very encouraging! I explained that I've been doing research everyday for 3 wks, and that I'd like fresh eyes on it because it may have been misdiagnosed. And that I hoped what I've learned would help.

Thank you again so much!! If only all retail counter staff were as knowledgeable as you!

 

[tjkj2002]

If a fuel injector "stuck open" you would not get a misfire since the amount of fuel that could leak past is not enough to cause a big issue besides messing up the fuel trims real bad.That would set off codes P0172(bank 1) or P0175(bank 2) depending on which bank has the leaking injector,at the same time the PCM would be cutting fuel to that whole bank thus reducing the amount of leaking fuel even father(to a point).

Now if they had the key in the "run" position without the engine running for a extended period of time or did not disable the fuel system while doing the compression test they could have "hydro locked" the engine.Once that happens you have a very small chance(like 5% or less) that no internal engine damage was done if it happened while at cranking rpm's and not at driving rpm's(1000 rpm's+).

Being as your current codes are for 2 different cylinders on different banks either they caused the codes and did not clear from testing of you have more than 1 issue to deal with.