Strange cap and rotor wear

Blake Stamper

Blake Stamper

TJ Enthusiast
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Joined
Jan 29, 2021
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417
Location
Boise, Idaho
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Hey y’all, I’ve been working on diagnosing a loud backfire at high rpms, I took the cap and rotor off and the wear seems very odd to me, is this normal and what could cause this? I’ll probably keep posting on this thread to keep you guys updated on what’s causing it.
 
I should add my jeep has already went through 2 caps and rotors in the last year and this cap and rotor only has like 6,000 miles on it
 
With the corrosion/material transfer taking place on one edge of the distributor caps contacts, it appears the rotor is not in phase when it fires.
Secondly, the distributor cap doesn't look like a very high quality cap, because it has aluminum terminals. Get a cap and rotor with contacts made of brass or copper. It's a good policy to buy high quality ignition parts, especially with our finicky Jeeps.
 
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flyinfish said:
it appears the rotor is not in phase when it fires.
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This is the problem. Since your ignition system is crank fired (the cam sensor in the distributor fires the fuel injectors) I would try @flyinfish suggestion of a high quality cap & rotor. If that doesn’t fix the problem, check the timing chain for stretch/wear.
 
flyinfish said:
With the corrosion/material transfer taking place on one edge of the distributor caps contacts, it appears the rotor is not in phase when it fires.
Secondly, the distributor cap doesn't look like a very high quality cap, because it has aluminum terminals. Get a cap and rotor with contacts made of brass or copper. It's a good policy to buy high quality ignition parts, especially with our finicky Jeeps.
Click to expand...

A shop did it for me, so I didn’t buy either of those, I replaced both when I swamped the engine and since then I’ve had to replace both twice now
 
Daryl said:
This is the problem. Since your ignition system is crank fired (the cam sensor in the distributor fires the fuel injectors) I would try @flyinfish suggestion of a high quality cap & rotor. If that doesn’t fix the problem, check the timing chain for stretch/wear.
Click to expand...

And it definitely has some form of timing problem with the backfire, the motor came with a bad head and I’m wondering if it also has a weak valve spring messing up the timing aswell
 
okay so update, after looking at the distributor I noticed I had a decent bit of side to side play, is this normal or could it be the fault causing both the bad wear and the backfire?
 
Im guessing distributor gear has wear- keep us posted.

Your post says you will “probably “ post on this thread. We will probably respond then 🤣
 
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Blake Stamper said:
I can’t buy just a bearing for it right, just have to buy a new distributor?
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I’m not sure buddy I haven’t had a distributor equipped vehicle in a long time but some of the guys on here will know for sure- I feel pretty confident that it’s going to work out good for you
 
AndyG said:
I’m not sure buddy I haven’t had a distributor equipped vehicle in a long time but some of the guys on here will know for sure- I feel pretty confident that it’s going to work out good for you
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I’m probably not as confident as ANDY G. of it working out well
 
AndyG said:
Oh its easy to be- not my Jeep🤣🤣
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No, that’s not it at all. I believe I’m not as confident of an easy solution because I don’t possess the ability to draw on the vast knowledge of the many various committees that your either a member of or the head of such
 
GPK03X said:
No, that’s not it at all. I believe I’m not as confident of an easy solution because I don’t possess the ability to draw on the vast knowledge of the many various committees that your either a member of or the head of such
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My vast network of resources and titles opens so many half doors for me- Which is good because I get them slammed in my face all the time🤣🤣
 
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Distributor body is probably worn. Been running mine like that for awhile on 1 cap and rotor without issues, yours must far more out of tolerance.
 
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