AMC 360 fluctuating RPM issue.

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   Hey guys, I got a question regarding my AMC 360. The 360 seems to be fluctuating from 600rpm to about 1100rpm after about 30min or so once the engine has been running for awhile. The engine itself has been board over .30, RV cam, DUI distributor, Howell throttlebody with 360 chip, Electric fans, 140 alternator, gear reduction starter, headers ( there is a very small pinhole after the collection location but the O2 sensor is located on the opposite side), Dakota digital gauges, etc... 

Any suggestions into tracking down what this could be? The engine does not shut off or hasn't so far. 

Thanks and if you need anymore info please ask. I am driving the jeep now with no issues, but it just seems strange that the engine would jump so far and adjust itself so much from 600 to 1100rpm. 

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GDAWG1007 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Jun/29/2013 Location: Savannah, GA Status: Offline Points: 79	Post Options Post Reply Quote GDAWG1007 Report Post Thanks(0) Quote Reply Topic: AMC 360 fluctuating RPM issue. Posted: Sep/15/2014 at 12:44pm
	Hey guys, I got a question regarding my AMC 360. The 360 seems to be fluctuating from 600rpm to about 1100rpm after about 30min or so once the engine has been running for awhile. The engine itself has been board over .30, RV cam, DUI distributor, Howell throttlebody with 360 chip, Electric fans, 140 alternator, gear reduction starter, headers ( there is a very small pinhole after the collection location but the O2 sensor is located on the opposite side), Dakota digital gauges, etc... Any suggestions into tracking down what this could be? The engine does not shut off or hasn't so far. Thanks and if you need anymore info please ask. I am driving the jeep now with no issues, but it just seems strange that the engine would jump so far and adjust itself so much from 600 to 1100rpm.
	1979 CJ-5 Renegade AMC 360, T-176, Dana 300, One Piece AMC 20 Axle 4:10 Gears, Dana 30 4:10 Gears, etc

tufcj Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Supporter of TheAMCForum Joined: Jul/10/2007 Location: Watkins, CO Status: Offline Points: 4083	Post Options Post Reply Quote tufcj Report Post Thanks(0) Quote Reply Posted: Sep/15/2014 at 12:55pm
	Do you hear rushing air like a massive vacuum leak? When I installed my Howell EFI, the throttle plates on the TBI were too far closed, causing the IAC (idle air control) to open too far. I had to remove the pressed in cap for the throttle plate adjustment screw. We disconnected the IAC, a friend had a tool to close it manually, then adjusted the idle to about 500 RPM with the throttle plates. Plugged in the IAC and let the computer adjust to 750. No more WHoosh, and a much smoother idle. Bob tufcj
	69 AMX 74 Javelin AMX 67 Rogue If you need a tool and don't buy it... you'll eventually pay for it... and not have it. Henry Ford

GDAWG1007 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Jun/29/2013 Location: Savannah, GA Status: Offline Points: 79	Post Options Post Reply Quote GDAWG1007 Report Post Thanks(0) Quote Reply Posted: Sep/15/2014 at 1:03pm
	Well I don't recall hearing any noice like air rushing out or being sucked in but I'll try to check this evening with some starter fluid or just try to hear the air. I do however have some PCV hooked up into the wrong ports according to the diagrams I have been finding off-line.
	1979 CJ-5 Renegade AMC 360, T-176, Dana 300, One Piece AMC 20 Axle 4:10 Gears, Dana 30 4:10 Gears, etc

greasygt III Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: May/27/2014 Location: Florida Status: Offline Points: 676	Post Options Post Reply Quote greasygt III Report Post Thanks(0) Quote Reply Posted: Sep/15/2014 at 1:53pm
	How are the fans wired? Disconnect the power to the fan and see if it will shut off.
	83 Spirit GT 79 Ranchero GT 460

AMX1972 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Oct/11/2008 Location: Massena Iowa Status: Offline Points: 161	Post Options Post Reply Quote AMX1972 Report Post Thanks(0) Quote Reply Posted: Sep/15/2014 at 6:47pm
	Does the howell injection use a throttle position sensor of some kind? If the throttle blade is open too far it can cause this issue too on many injection systems. You might need to adjust the TPS to reset it to a level that is recognized as "idle". If the blades are open too far it will bypass the idle settings and go into a surge. Resetting the TPS to an idle voltage will make it use the idle settings and stop surging. I don't know what voltage range your setup wants, some systems use .99 volts as the breakover from idle to "cruise".
	1972 Javelin AMX T/A Red 360/4 speed 1968 AMX "The Pied Piper" "Cam Only" 390/727 1/8th mile bracket racer on E-85. 10.92@121.9 mph.

FSJunkie Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4742	Post Options Post Reply Quote FSJunkie Report Post Thanks(0) Quote Reply Posted: Sep/15/2014 at 7:51pm
	Bad timing sets do funky things. Just found that out myself yesterday. You can bash your head against your motor for months and change, test, and tune just about everything until you're ready to drop-kick it, but it'll never run right if that timing chain is shot.
	1955 Packard 1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited

uncljohn Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jan/03/2013 Location: Peoria AZ Status: Offline Points: 5394	Post Options Post Reply Quote uncljohn Report Post Thanks(0) Quote Reply Posted: Sep/15/2014 at 9:46pm
	Just out of curiosity does this fuel injection system have any self test diagnostics built into it? I have scan tools to be able to read the diagnostics for the fuel injection I use on my Spirit which is based on the 94 Jeep unit, or basically that vintage mopar and it is an OBD-I era system. My Saturn is PRE-OBD-I and I have one that will read it too. I find it very valuable to have that capability. Also both have a form of self test that can be used with out a scan tool where it flashes error codes through he check engine light. What you are describing seems to me the system is sensing a mixture problem and attempting to compensate which seems a little tricky to guess at. Because it should also sense rpm and try to deal with that too.
	70 390 5spd Donohue 74 Hornet In restoration 76 Hornet, 5.7L Mercury Marine Power 80 Fuel Injected I6 Spirit 74 232 I-6, 4bbl, 270HL Isky Cam

GDAWG1007 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Jun/29/2013 Location: Savannah, GA Status: Offline Points: 79	Post Options Post Reply Quote GDAWG1007 Report Post Thanks(0) Quote Reply Posted: Sep/17/2014 at 12:08pm
	Thanks guys. I was in the process of checking some of your suggestions when my T176 transmission would not shift into first or second. The transmission shifts fine when the engine is off, but once it warms up the transmission won't let me shift into gear. Any thoughts? I'm thinking it has to be a synchronizer, but have found some post on line saying it could be the clutch. This engine swap and transmission overhaul was supposed to eliminate all this headache... Hahaha it hasn't.
	1979 CJ-5 Renegade AMC 360, T-176, Dana 300, One Piece AMC 20 Axle 4:10 Gears, Dana 30 4:10 Gears, etc