Are spark plugs and wires from AutoZone or O'Reilly's any good?

Jerry Bransford said:
I kinda doubt you'll see anything unusual on the fuel injector pulse with the scope though it'd be interesting. Should be nothing but a clean low frequency square wave. I'd next swap the #1 injector with one of the others and see if the misfire follows the #1 injector to the new location or if the misfire remains at the #1 location.

Early 97-98 4.0L engines had misfire problems caused by a bad (weak) set of valve springs the factory received. Replacing the springs was the fix for that. The same p/n valve springs are used, the bad valve springs were removed from the system.
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Jerry,

I've already swapped injectors around to see if the misfire moved off of cylinder #1, and it didn't. So, I know my fuel injector is fine. I also tested the resistance of each injector and they all read around the same resistance.

Oh brother, valve springs? That sounds like it might be a painful DIY project. I'll have to do some research to see what I can do to confirm that it's a valve spring issue before jumping into replacing them. The misfire is sort of intermittent, which means that it can quite possibly be a weak valve spring that sometimes springs and sometimes doesn't.
 
My '97 TJ 4.0 had intermittent misfires in multiple cylinders which were fixed by new springs. Jeep came out with a TSB for the weak spring issue causing random misfires.

Have you performed a compression test yet?
 
Jerry Bransford said:
My '97 TJ 4.0 had intermittent misfires in multiple cylinders which were fixed by new springs. Jeep came out with a TSB for the weak spring issue causing random misfires.

Have you performed a compression test yet?
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I just did a compression test. Cylinder 1 was reaching 60psi, cylinder 2 reached 120psi, and I concluded my efforts then. I put a bit of engine oil into cylinder 1 and the pressure spiked to 150psi, which from my research indicates that it's a bad piston seal.
 
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Jerry Bransford said:
My '97 TJ 4.0 had intermittent misfires in multiple cylinders which were fixed by new springs. Jeep came out with a TSB for the weak spring issue causing random misfires.

Have you performed a compression test yet?
Click to expand...

Jerry, I talked to a mechanic whose shop is across the street from my office and he thinks I should just swap the entire motor out with a crate motor instead of fixing the piston ring... what do you think about this? The engine only has 124k miles on it... it received a brand new head about 6k miles ago because the exhaust valves were leaking due to bad seating. I just feel like an engine swap would just be a much more costly solution.
 
Daniel.Lee said:
Jerry, I talked to a mechanic whose shop is across the street from my office and he thinks I should just swap the entire motor out with a crate motor instead of fixing the piston ring... what do you think about this? The engine only has 124k miles on it... it received a brand new head about 6k miles ago because the exhaust valves were leaking due to bad seating. I just feel like an engine swap would just be a much more costly solution.
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I didn't mention replacing any piston rings, what fixed my 97 TJ's misfires were new valve springs which is a relatively minor job. Including all new springs and labor the job was somewhere around $300, most of that was the couple hours of labor required.
 
Jerry Bransford said:
I didn't mention replacing any piston rings, what fixed my 97 TJ's misfires were new valve springs which is a relatively minor job. Including all new springs and labor the job was somewhere around $300, most of that was the couple hours of labor required.
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Jerry, but can't I conclude that it's the piston rings that are giving me trouble? So I can rule out the valve springs, right? When I put engine oil into the cylinder the pressure spiked to 150psi. From my understanding, the oil creates a temporary seal at the piston ring and allows for proper compression.
 
Daniel.Lee said:
Jerry, but can't I conclude that it's the piston rings that are giving me trouble? So I can rule out the valve springs, right? When I put engine oil into the cylinder the pressure spiked to 150psi. From my understanding, the oil creates a temporary seal at the piston ring and allows for proper compression.
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Oh gotcha, I think I'm still reeling from the fumes of spraying Rustoleum truck bed liner an hour ago in my garage lol. I scrolled further up and now get what you are referring to. I really don't know if I'd go with the crate motor or just have someone drop the crank and replace the rings. It'd be time for a second opinion.
 
Howdy everyone. Following this thread as I too have been having a #1 cylinder misfire code that pops up, clears with a battery disconnect, then comes back at random times. I noticed mine comes and stays for the summer, like an unwanted guest, then when it cools off (In AZ that feels like never,lol) one cool/cold morning, I'll go fire it up and boom! No code.

for info: Mine is a '97 4.0L Sport. with only 101K original miles on it. driven maybe 1000 miles a year for trips and such.

Have already replaced all the wires and plugs, cap and rotor (done when i purchased it a while back), as well as have a mechanic check things out (twice). Both times, they have cleared the code, ran the jeep but the code did not come back at anytime they had the vehicle. As its not a daily driver, I left it with the second one for weeks to attempt to reproduce the code. No luck.

I have read online through many, many, many forums, videos, talks, etc, that it could be anything from a dang TPS sensor (did I say that right?) to faulty wiring, cap, rotor, cracked valve, weak springs....the list goes on and on.

Was going to look into swapping the injectors to check if the code moves (or even just replacing them with manufactured OEM). But after reading what steps Daniel has taken, I wouldnt mind waiting to find out what he has eventually settled on before I just end up tearing the dang thing down and spend money I would like to use elswhere on a rebuild that I don't want to do considering the low(ish) miles.
 
Galxy412 said:
Howdy everyone. Following this thread as I too have been having a #1 cylinder misfire code that pops up, clears with a battery disconnect, then comes back at random times. I noticed mine comes and stays for the summer, like an unwanted guest, then when it cools off (In AZ that feels like never,lol) one cool/cold morning, I'll go fire it up and boom! No code.

for info: Mine is a '97 4.0L Sport. with only 101K original miles on it. driven maybe 1000 miles a year for trips and such.

Have already replaced all the wires and plugs, cap and rotor (done when i purchased it a while back), as well as have a mechanic check things out (twice). Both times, they have cleared the code, ran the jeep but the code did not come back at anytime they had the vehicle. As its not a daily driver, I left it with the second one for weeks to attempt to reproduce the code. No luck.

I have read online through many, many, many forums, videos, talks, etc, that it could be anything from a dang TPS sensor (did I say that right?) to faulty wiring, cap, rotor, cracked valve, weak springs....the list goes on and on.

Was going to look into swapping the injectors to check if the code moves (or even just replacing them with manufactured OEM). But after reading what steps Daniel has taken, I wouldnt mind waiting to find out what he has eventually settled on before I just end up tearing the dang thing down and spend money I would like to use elswhere on a rebuild that I don't want to do considering the low(ish) miles.
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Hey, thanks for posting.

So basically I still have my misfire. I ended up taking my car to the shop a few days ago and they came back telling me that my springs look good, valves look good, everything looks good. The shop then performed a leak down test and found there was 80% leakage and that it sounded loudest from the intake. Now, they told me that the leakage should have shown around 15% so there is obviously something wrong here.
They are now recommending that I remove the cylinder head and have it sent to a machine shop for inspection, valve grind, and surface. They quoted me $3,000.......

Now, here's where I am scratching my head. The previous owner of my vehicle was having cylinder misfire issues with cylinder #5 so he took it to a reputable shop exactly 1 year ago where they discovered that all of the exhaust valves were leaking badly and cylinder #5 was the worst of them all. The cylinder head was sent to a machine shop where they inspected it and found badly worn valve seats. $4221.11 later, the previous owner walked out with the vehicle and it had zero problems until he sold it to me.... Now here I am with the same exact problem the previous owner had 1 year ago. I'm going to take the car to the shop that did the cylinder head rebuild last year and ask them if they are willing to redo the work at cost. I have the invoice from the previous owner and at the bottom in small text it says that there is a 24 month, 24,000 mile warranty on their work. However, the warranty doesn't transfer to subsequent owners of the vehicle.

Sigh.
 
Three to Four Grand for a valve job!?! Fucking absurd.
Excuse my language. We ain't working with Ferrari's here. These heads are about as sophisticated as a tractor.
 
Parts sounds about right. A quick google search gave me a remanufactured head for $500. Their labor rate must be astronomical.
 
Last shop I was in was a driveline and gear shop and it was $110/hr., a month or so ago. But 12+ hours to replace a Jeep head sure sounds excessive. I'm sure someone will correct me if I'm wrong.
 
twistedlv said:
Last shop I was in was a driveline and gear shop and it was $110/hr., a month or so ago. But 12+ hours to replace a Jeep head sure sounds excessive. I'm sure someone will correct me if I'm wrong.
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Ah, $110/hr isn’t much cheaper than $150/hr. I was honestly expecting you to say $80/hr or something like that. I wonder if driveline and gear shops charge more because they’re more of a specialty shop? I don’t know. Also, I think a lot of the labor cost is from the machine shop. I bet their labor rates are even higher.
 
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