4.7 Stroker Issues - 2002 Wrangler X

ChrisHoward417

ChrisHoward417

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Jan 23, 2024
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Cookeville, TN
Background - Before I swapped engines, when it had the stock 4.0, I had issues with the ignition cutting out. I'd be driving along and out of nowhere it was like it would go into a limp mode or something for a few seconds, then it would pick back up. Took it to a buddy who is a mechanic and he said the wiring harness had gotten hot, so we separated all the wires, ran better for awhile but would still randomly do this.

Replaced the engine with a Spartan 4.7 long block. Every bolt on part was replaced. New injectors, MSD ignition rail, water pump, alternator, etc. I'm still having the same issue with it cutting out/going into limp/whatever its doing. Had an engine code pop up, "Misfire Cylinder #3".
I feel like everything mechanically is good, I'm leaning towards electrical.

Has anyone else had an issue like this with a bad wiring harness? Where do I get a replacement, Painless doesn't make one and they're discontinued from Jeep. Do I need my computer reprogrammed, and where do I have that done?

Sorry for being so long, thanks for any help/advice
 
I like your style... wiring harness issues... solution... replace engine with stroker.

My kind of a solution.

-Mac

P.S. sounds like you need to spend a fun and exciting many hours of time checking continuity on just about every wire in that Jeep...the FSMs in the resources section have the wiring diagrams. Could start with ignition or injector wires. Have you replaced the switch or actuator pin?
 
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ChrisHoward417 said:
Background - Before I swapped engines, when it had the stock 4.0, I had issues with the ignition cutting out. I'd be driving along and out of nowhere it was like it would go into a limp mode or something for a few seconds, then it would pick back up. Took it to a buddy who is a mechanic and he said the wiring harness had gotten hot, so we separated all the wires, ran better for awhile but would still randomly do this.

Replaced the engine with a Spartan 4.7 long block. Every bolt on part was replaced. New injectors, MSD ignition rail, water pump, alternator, etc. I'm still having the same issue with it cutting out/going into limp/whatever its doing. Had an engine code pop up, "Misfire Cylinder #3".
I feel like everything mechanically is good, I'm leaning towards electrical.

Has anyone else had an issue like this with a bad wiring harness? Where do I get a replacement, Painless doesn't make one and they're discontinued from Jeep. Do I need my computer reprogrammed, and where do I have that done?

Sorry for being so long, thanks for any help/advice
Click to expand...

Although I’m not certain, I would think a stroker would require a tune. I don’t know if the stock tune can compensate for the additional air. I’m sure someone with knowledge will chime in.

You could try Davey’s Jeep for a used harness.
 
NashvilleTJ said:
Although I’m not certain, I would think a stroker would require a tune. I don’t know if the stock tune can compensate for the additional air. I’m sure someone with knowledge will chime in.

You could try Davey’s Jeep for a used harness.
Click to expand...

They could all benefit from a tune.one from ryan is on my wishlist.But if things like cam spec,quench,compression ratio aren't too wild it isn't necessary.
 
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macleanflood said:
I like your style... wiring harness issues... solution... replace engine with stroker.

My kind of a solution.

-Mac

P.S. sounds like you need to spend a fun and exciting many hours of time checking continuity on just about every wire in that Jeep...the FSMs in the resources section have the wiring diagrams. Could start with ignition or injector wires. Have you replaced the switch or actuator pin?
Click to expand...

The stroker replacement was actually for a busted piston and cylinder wall. But if replacing the engine why not go bigger, right? I didn't replace the switch but the part that runs from the key switch under the column to the other side broke. I wired in a push button from TSC. But right now its wired straight to the starter. I suspected I would have to replace the harness. If I was more capable I would build one.
 
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ChrisHoward417 said:
The stroker replacement was actually for a busted piston and cylinder wall. But if replacing the engine why not go bigger, right? I didn't replace the switch but the part that runs from the key switch under the column to the other side broke. I wired in a push button from TSC. But right now its wired straight to the starter. I suspected I would have to replace the harness. If I was more capable I would build one.
Click to expand...

Why not just get another ignition actuator? They aren't hard to install or very expensive
images (1).jpeg
 
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NashvilleTJ said:
Although I’m not certain, I would think a stroker would require a tune. I don’t know if the stock tune can compensate for the additional air. I’m sure someone with knowledge will chime in.

You could try Davey’s Jeep for a used harness.
Click to expand...

Not to derail OP too much (I agree wiring sounds like the culprit), Golen says their 4.6 is good with a stock tune with 24# injectors (instead of stock 18#). Mine runs well in that configuration. I have considered a tune and even talked to a local guy and Flyin' Ryan. They both said they didn't expect big peak gains but perhaps some "area under the curve" improvement would be noticeable in more normal (non-WOT) driving. It's on my list.
 
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I d guess that your pre-stroker run issue is still lingering.

The stroker may not run at totally optimum efficiency without a tune but should run well…. You ve got a hidden gremlin still lingering ….
 
I would start with detaching every connection point use contact cleaner and coat pins with dielectric grease
 
Ok.so to circle back around to diagnosis,the cyl three misfire is the only code? Are you sure it is ignition and not fuel? Have you done any of the heat soak prevention measures that affect the center cylinders? What injectors did you get?new?maybe have them tested?fuel psi under load?

Leakdown tester shows the motor is actually healthy?

I've never heard of "my wiring harness got hot" ? Is the insulation crumbling or melted?not saying it isn't ignition related(or a broken wire at injector 3 like i had) that just sounds strange
 
Rickyd said:
Ok.so to circle back around to diagnosis,the cyl three misfire is the only code? Are you sure it is ignition and not fuel? Have you done any of the heat soak prevention measures that affect the center cylinders? What injectors did you get?new?maybe have them tested?fuel psi under load?

Leakdown tester shows the motor is actually healthy?

I've never heard of "my wiring harness got hot" ? Is the insulation crumbling or melted?not saying it isn't ignition related(or a broken wire at injector 3 like i had) that just sounds strange
Click to expand...

I haven't done a leak down test as its a new reman engine from Spartan, new reman injectors flow tested to +/- 1% from South Bay Injectors, new MSD coil pack/ignition rail, new Bosch sparkplugs, etc.
When the problem initially started, (when the 4.0 was still in the Jeep), we pulled the top cover off the engine wiring harness, where the injector leads come off, and it was all sort off melted together. We separated everything and it helped for a little while
 
So, this may be a crazy approach, but in the OP's first post he mentioned the previous engine cutting out, which reminded me of a similar frustrating condition on my old '83 Scrambler. My ultimate solution was a new ECU, even back then. Instantly fixed my problem.

Maybe I missed it, but it sounds like you had a problem before the stroker install?
 
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