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Author Topic: AMC 360 misfire  (Read 204 times)

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Offline Zooguy

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AMC 360 misfire
« on: December 22, 2020, 08:46:42 PM »
Sorry for the rehashed topic but I am out of ideas. Any suggestions will help. Here it goes.
I have an 83 CJ7 with an AMC 360 and Holley quick fuel 600
From day one on a full rebuild it has had a misfire, making it stressful to drive. I have...
-Replaced the fuel lines and and filters
-Re-jetted it
-New plugs, wires and cap
-Tried a different distributor
-Changed the cam shaft and lifters
-New coil
-Checked and changed all vacuum lines
-Timing is checked
-Air filter is new
-checked engine ground
-fuel pressure gauge at 6lbs
-compression is fine
What have I missed.. Thanks


« Last Edit: December 22, 2020, 08:53:29 PM by Zooguy »

Offline hps4evr

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Re: AMC 360 misfire
« Reply #1 on: December 23, 2020, 06:31:01 AM »
Can you pin-point which cylinder is misfiring? Or is it a random misfire on all cylinders?
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Offline Zooguy

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Re: AMC 360 misfire
« Reply #2 on: December 23, 2020, 10:50:30 AM »
I think it is just random.

Offline Zooguy

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Re: AMC 360 misfire
« Reply #3 on: December 23, 2020, 10:59:03 AM »
file:///var/mobile/Library/SMS/Attachments/ee/14/DC6693A8-5085-41AD-AFD1-73673CFC3346/FullSizeRender.jpg
file:///var/mobile/Library/SMS/Attachments/37/07/201F3C0A-2D08-4AA1-981B-0858818351B5/IMG_5259.JPG

Offline Vinman

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Re: AMC 360 misfire
« Reply #4 on: December 23, 2020, 12:03:35 PM »
Check all the electrical wiring between the coil and battery. Could be an intermittent break in connection anywhere in the circuit, ignition switch, etc.

I had a GM many years ago that would have a  random sputter and it turned out to be a bad wire in the distributor below the rotor cap, it was hell to track down.
/l ,[____],
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Quote from: Bnine link=topic=25904.msg162940#msg162940      date=1341881306

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Offline Zooguy

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Re: AMC 360 misfire
« Reply #5 on: December 23, 2020, 05:39:51 PM »
Perfect, I will give it a shot.

Offline hps4evr

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Re: AMC 360 misfire
« Reply #6 on: December 23, 2020, 05:44:06 PM »
Check for any vacuum leaks. Also, I can’t recall but what ignition system does this use? Is there an ignition box that can be going bad? I know Ford and chrysler in these years had issues.
YJ=Y’all Jealous

Offline Zooguy

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Re: AMC 360 misfire
« Reply #7 on: December 23, 2020, 08:12:12 PM »
I will double check the vacuum but I think I have checked it all. I don’t think I have an ignition box. I have a MSD 8523 distributor with electronic points and a blaster 2 coil. The guy who wired it did a poor job, a lot of loose wires and bad grounds. Aside from the misfiring problem, I have had signal, dash light, stereo issues. All down to poor wiring. It is not my strong point to diagnose either. Thanks for the input, I will take another look.

Offline hps4evr

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Re: AMC 360 misfire
« Reply #8 on: December 23, 2020, 10:22:23 PM »
Maybe pull valve covers off and make sure each valve is opening all the way. Wiped out cam lobe or collapsed lifter.
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Offline cLAY

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Re: AMC 360 misfire
« Reply #9 on: January 01, 2021, 11:56:45 PM »
Is it consistent or completely random?

Consistent
 Maybe need to check the timing chain. How much advance are you running? How much compression?  Premium fuel vs regular make any difference?

Random
-any trend to it? After idling? Getting on throttle hard? Ambient temp? 

Does it just miss or stall right out?
Incompetence - When you earnestly believe you can compensate for a lack of skill by doubling your efforts, there's no end to what you can't do.
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Offline Zooguy

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Re: AMC 360 misfire
« Reply #10 on: January 07, 2021, 09:24:53 PM »
Sorry for the late response, I haven’t had time in the Jeep the last little while. It is unfortunately relatively consistent. The timing chain is fine, advance is about -8 and the compression is fine across the board. I think around 120-130 ish. With the older style engine I have been told 87 octane is all I need I and am sure I have tried 91 with no differences. The trends of the miss fire are a bit weird. Starting is fine but the last couple test drives it started to miss fire at the same point in the drive about 10 minutes in. Totally fine up to that point. If I let off the throttle it will completely stall but if I give it full throttle it will get fumed off but keep running, barely. I can usually get it back home. If it does stall, I wait one minute then it starts fine but will get tempermental right off the start. Ambient temperature doesn’t seem to matter. I am going to try to solder some of the wires off the distributor this weekend to see if that helps. It was running pretty hot also if I tried to drive it for long. Valves are good. We have tried to tune the carb but last time I think we made it worst with the high speed idle. Jets are good though. I am hoping the soldering and a carb adjustment this weekend might help but it am losing faith in it being reliable for a drive. It’s almost completely rebuilt. 
Thanks for reading this novel.
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Offline Zooguy

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Re: AMC 360 misfire
« Reply #11 on: January 08, 2021, 08:59:19 PM »
I’ve been searching the web and maybe a loose Tach wire is causing it...maybe. I’ll check tomorrow.

Offline Vinman

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Re: AMC 360 misfire
« Reply #12 on: January 08, 2021, 10:06:47 PM »
I think you’re on the right track with it being and electrical issue. Keep plugging away and check every electrical connection you can find. Maybe start shaking all the wiring harnesses while it’s running to see if you can replicate it.
Just spit-balling here but maybe spray water over all the engine electrical connections with the engine running to see if you can find a weak link?

/l ,[____],
 l---L -OlllllllO-
 ()_)-()_)-o-)_)

Quote from: Bnine link=topic=25904.msg162940#msg162940      date=1341881306

 Resident prick is my job and it took me ten years to earn that title

Offline Zooguy

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Re: AMC 360 misfire
« Reply #13 on: January 09, 2021, 08:08:57 PM »
Checked the wiring today and it seemed to help. I solder a few that looked weak. It was one of my better test drives. I thought I would try to adjust the carb while i was at it and noticed something a bit strange.  I can tighten the idle screws on either side of the carb all the way and it doesn’t stall. Why is that? High speed feels better and I turned the secondary screw out a bit. The only time the jeep seemed to have trouble is when I gave it too much gas too quickly. It then stuttered and I had to back off. It will get to speed but I have to get it there slowly. But a step in the right direction. 

Offline cLAY

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Re: AMC 360 misfire
« Reply #14 on: January 12, 2021, 01:49:27 AM »
Everything here sounds to me like a carb issue, not spark. Especially cranking down the mixture screws not having much effect.  Do you have a vacuum guage? Thats the best way of tuning a carb short of putting an O2 sensor in the exhaust. Without one your best best is to tune mixture screw for highest idle, reset idle screw, recheck timing, then reset mixture screw again and recheck everything still it stays the same. Also make sure the choke is fully opening.

Pull the plugs, sooty black-running rich

Check for vacuum leaks, brake booster diaphram and distributor vacuum line are often overlooked culprits.

Fuel boiling in the lines or carb bowls can cause theses symptoms as well. Does it have a fuel return? Lines routed too close to exhaust.

I don't know anything about the Holley quickshot, but I played with lots of older Holleys. Pain in the arse, everyone of them. Way too much adjustability and super finicky. Floats bounced on every big bump offroad causing a floodout, Steep climbs caused bowls to overflow, floodout. Had to rest mixture and choke settings at every season change. Tried all sorts of tricks, spring loaded needle and seats, overflow tubes, etc. Ended up going to an Edelbrock Truck Avenger carb and having WAY less issues.

What did you put in for a cam? Anything radical? Still idles nice or lopes?
Incompetence - When you earnestly believe you can compensate for a lack of skill by doubling your efforts, there's no end to what you can't do.
The only work I've done on a Rubi involved a chainsaw....

'93 ZJ, 5.2L, lifted/locked/36s..<gone>
'98 5.9e