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Unread 06-22-2014, 09:00 PM   #1
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1988 YJ Wrangler 
Join Date: Dec 2010
Location: Boise, ID
Posts: 45
Loud clicking from engine under load

I am getting a loud clicking sound from my engine when i pull a grade. I had originally thought it was transmission related but have ruled that out with my AX15 swap and new clutch.

Do any of you engine gurus have a thought about what is going on in there? I have 175K on the clock. Is it getting ready to go on me?



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Unread 06-23-2014, 12:36 AM   #2
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1990 YJ Wrangler 
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Location: Central Oregon!
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What's your timing set at?
1990 YJ-The wheeler
2015 JK- The DD
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Unread 06-23-2014, 08:18 AM   #3
Mike Romain
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1986 CJ7 
Join Date: Nov 2007
Location: Off the Grid in Chester Grant, Nova Scotia, Canada
Posts: 17,557
I use the phone android app so can't see profiles or SIG lines. Just guessing that your timing might be advanced too much if you have the 258. That said, the CJ owners manual on the 258 states it is supposed to rattle under load on a hill. This is normal and a sign that you need to downshift. If it still pings under heavy load or running hot, the manual recommends high test gas.

I got 5 mpg better running high test on my 258 with the timing set to 9 btdc with way better throttle response. I figure an extra 100 miles per tank was well worth the extra $7.00 or so a fill.
86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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Unread 06-23-2014, 12:40 PM   #4
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1991 YJ Wrangler 
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Location: Meadville, Pa
Posts: 1,124
check your intake and exhaust gaskets for leaks
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Unread 06-23-2014, 12:56 PM   #5
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1988 YJ Wrangler 
Join Date: Jun 2013
Location: Whittier, CA
Posts: 1,229
I agree that it is probably pinging - detonation - knock. All terms for the same thing.

The key is the Howell EFI kit. I've been tweaking my timing after the Howell install. The engine originally had a knock sensor which would retard the timing as needed to avoid knock.

Now you don't have a knock sensor, and the GM throttle body ported vacuum source connected to the distributor vacuum advance has a different pressure profile than the stock Carter carb. Plus you have eliminated the PCM and the ICM no longer has the ability to adjust timing for you. You have to go old school on it.

I'm still working on exactly where I want mine. But to stop the pinging it is an easy adjustment. Get a 1/8" allen wrench. Pull the vacuum hose off the distributor. Stick the allen wrench in the vacuum nipple and find the set screw. Turn it counterclockwise about 2 turns. Then test drive. Go another turn, test, repeat as necessary until the pinging under load just stops. Count the total number of turns and make a note for yourself so you can reverse it if you don't like the result.

Then research timing profiles over in the CJ forum for more in depth instructions on perfecting the timing mechanical and vacuum advance. The above should be used just to prove that it is indeed pinging, and not something else. The CJ forum has better info on the 4.2 than the YJ forum.
Dodge did not build my Jeep.
1988 Wrangler,4.2L I-6, Howell EFI JP-1,GM HEI Ign, 5 Speed Peugeot, Zone 2.5" lift + 1/2" booms, BFG 31 x 10.5, Bestop.
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