2000 Jeep Cherokee 4.0, auto, 125,000 mi.

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#31
To state my question in a "catch-all" way...is the problem still an intermittent lack of performance by cylinders 1 and 6?

If wiggle tests or visual and resistance tests produce no results, my strategy for suspected harness problems is to cut the suspect wire (at both ends) and run a new (temporary) wire. If the suspect circuit includes a splice or two, then it is necessary to make a mini-harness. Creating a redundant circuit can fix an open circuit type of failure, but removing the suspect wire completely (cut both/all ends) also eliminates possible short-to-ground or short-to-another-circuit.

I don't have a magic bullet, but adding a new wire can also provide ready access to a fresh diagnostic checkpoint.

DRBIII (drb three) is the name of the dealership scanner from that era that might be most helpful.

Classic harness problems on that model are in the valve cover/ firewall area. Also multiple ground connections on passenger side of engine block.
 

Darren

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#32
To state my question in a "catch-all" way...is the problem still an intermittent lack of performance by cylinders 1 and 6?

If wiggle tests or visual and resistance tests produce no results, my strategy for suspected harness problems is to cut the suspect wire (at both ends) and run a new (temporary) wire. If the suspect circuit includes a splice or two, then it is necessary to make a mini-harness. Creating a redundant circuit can fix an open circuit type of failure, but removing the suspect wire completely (cut both/all ends) also eliminates possible short-to-ground or short-to-another-circuit.

I don't have a magic bullet, but adding a new wire can also provide ready access to a fresh diagnostic checkpoint.

DRBIII (drb three) is the name of the dealership scanner from that era that might be most helpful.

Classic harness problems on that model are in the valve cover/ firewall area. Also multiple ground connections on passenger side of engine block.
That's probably what the new owner/dealer thought when he mentioned the newly taped wiring at the firewall. Which he didn't check because he thought it was already checked. Thanks for that info.
 

nickb2

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#33
Some of the garages have competent white-haired mechanics that have a lot of BTDT.
What does this mean. I am not used to some abbreviations and I am always learning english.

I fell upon this old thread and understand you are still in the market for this 4x$. And yes that was not a mistype.

This is where you need a scope. If the engine has compression, trans works fine, it may just be a calibration, but to catch that, you need to find a shop and a knowledgeable guy to hook up a scope to it. A 4.0l is near indestructible.

My opinionated advice is like an arsehole, everyone has one. But @ 1100$, what is the risk? If I could find a clean body jeep for that price were I live, engine could be in the trunk and I wouldn't care.

I know I spent some time on this thread maybe a few months ago, but was anything tried out? Or you are just looking at the damn jeep rotting in a lot?

Before I write anything else that may seem coarse, remember this. Without risk, no benefit. Looking at something doesn't make it better.
 

Eric1974

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#34
Here is just an idea. I had the same problem when I first bought my 2000 Jeep Cherokee with the 4.0. It was from California and has the emissions for that state. I fueled it up with 87 octane just like anyone would do and it was throwing cylinder miss codes. I replaced a few minor things including throttle positioning sensor, still the same result. When I needed to gas up again I fueled up with 89 octane and all that went away. It will not run good on 87 octane. I got the idea from a friend who knew someone who had a car that did the same thing, so I tried it, never a problem since then. Sucks to pay a tad more for gas but it's not really that much more and it remedied the problem. Worth a shot.
 

Darren

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#35
What does this mean. I am not used to some abbreviations and I am always learning english.

I fell upon this old thread and understand you are still in the market for this 4x$. And yes that was not a mistype.

This is where you need a scope. If the engine has compression, trans works fine, it may just be a calibration, but to catch that, you need to find a shop and a knowledgeable guy to hook up a scope to it. A 4.0l is near indestructible.

My opinionated advice is like an arsehole, everyone has one. But @ 1100$, what is the risk? If I could find a clean body jeep for that price were I live, engine could be in the trunk and I wouldn't care.

I know I spent some time on this thread maybe a few months ago, but was anything tried out? Or you are just looking at the damn jeep rotting in a lot?

Before I write anything else that may seem coarse, remember this. Without risk, no benefit. Looking at something doesn't make it better.
You are 1000% correct. At this point it is rotting in a lot. I've got too much on my plate to mess with it. I'll wait until Jan. or Feb. and make an offer.
 

jd

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#36
We nearly gave up on a car with a bad NEW pack. Four-Banger would drop two cylinders, only on occasion. Scanner reported the misfire correctly but it wouldn't fail in the shop...
Firing Order for a Chrysler 4.0L engine is 1-5-3-6-2-4 so it seems to me it uses a three-coil pack, or three single packs, each firing the power stroke cylinder and the waste spark cylinder. In this case 1+6, the two you have problems with, are common (like 5+2, and 3+4). So if you swapped coils and the problem stays on 1+6... Pack isn't being consistently triggered by the PCM or its connections or wiring.
 

billr

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#37
Alas, the OP can't try anything with this unless he "commits" by buying it.

There is another, uglier, scenario involving the 1-6 cylinder pair: an exhaust valve that sometimes fails to open. That could be from a bad lifter, or several other things if this is a push-rod engine (I suspect it is). If an exhaust valve occasionally doesn't open properly, at all or partially, that cylinder might well miss-fire. But so, too, could its partner cylinder, since the cylinder with a bad valve could build up enough compression pressure on the exhaust stroke to make the spark gap in the wasted cylinder hard to jump; thus lowering spark energy available in the firing cylinder.