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  • December 18, 2018, 05:57:59 AM

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Author Topic: need help, car idles fine, backfires and hesitates when throttle is applied  (Read 2896 times)

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Offline rommel1940

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So my can was basically running fine, a little pinging , been managing that with better gas.So I was under my hood installing aftermarket gages, volt, oil, water.In the process of that ,I moved the air cleaner, maybe a line or something else.So now the car still idles and starts great, seems like you can get in and go for a drive.But No, In parked idling if you apply the accelerator aggressively it will hesitate and backfire out of the carb,even want to stall, small movements not so much, but when you drive it bogs down with no power and will stall If I'm not careful. I inspected all vacuum hoses, checked the vaccum advance by pulling of the hose, it works.Its weird cause the car was fine, until I messed with the air cleaner and areas around the firewall and the oil pressure port by the oil filter, also install my water probe in a tee in the front intake port were the computer water sensor is.I cannot see anything that I could have messed up, I never touched the carb.I cannot drive my car, I also checked the fuel filter, that was good, Im frustrated
1984 Eagle Limited

Offline amcfool1

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hi, did you use a mechanical oil pressure gauge? and did you put it in place of the original  "idiot light" sending unit? if so, that may be your problem. The choke gets its power from the oil press sending unit. I did the same thing, but put a "TEE" adapter in the block, so I kept the original oil press sending unit, and had another port for the mechanical oil press gauge. good luck, gz

Offline amcfool1

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also, the computer water sensor is very important, it basically tells the computer to turn on at a certain temperature (CTS-Coolant Temperature Sensor) you may have messed it up just by fooling with it during removal, installation, just due to is age. New ones are still available, though not cheap.  Napa/Echlin # TS5019, about $55. I put my temp. probe directly in the water hose that goes from the rear of the intake to the heater vac switch assembly, using just a regular  hardware store "T", again, good luck, gz

Offline rommel1940

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I used a mechanical oil Guage at the port above the oil filter, and yes the water temp sensor is teed of the front intake port, I was thinking about the possibility that the coolant switch got messed up some how, it looks fine, was careful not to twist the wires, do you think that could cause it to run so terribly? I tried to put my water temp sensor at the back of the cylinder head but the thing was stuck pretty good and didn't want to break it.plus it still works..is there a way to test the coolant switch for the computer?
1984 Eagle Limited

Offline amcfool1

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yes there is a way to test it, macdude443 is the guy to ask about that. basically, you get a multimeter, and take a reading cold, and a reading hot, if there is no change, its bad (ohms, i think), also it may be as simple as a vac line disconnected accidentally. you should have a vac diagram right on the firewall. Take a deep breath, get a good light source, and follow it EXACTLY, replacing any lines that look marginal and/or old/cracked. trust me, it will eventually make sense. Pay special attention to the EGR routing, a wrongly connected or malfunctioning EGR can cause many of the symptoms you are describing. Also, though this is probably not your problem, make SURE all your grounds are good, ie batt to block, block to frame, ECM to block. (this is the flat "eye" connector bolted to the block just behind the coil.) BTW, what year is your Eagle? send an engine bay picture if you can. gz

Offline rommel1940

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1984 eagle stock engine bay,  original ignition module
« Last Edit: December 06, 2015, 10:13:44 AM by rommel1940 »
1984 Eagle Limited

Offline amcfool1

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hi, any progress?

Offline rommel1940

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No I flooded the car so bad it wouldn't say running last night, well I did test the coolant switch and computer, there working.i keep looking at all the vaccum lines and cannot find anything wrong but when I was walking around my car I found this 9 inch piece of vaccum tube, it looks like it came from my car but I cannot find its home.car as of right now starts and idles well, no noticeable vaccum sounds, but as soon as you give it some decent throttle, it will back fire though the carb and loose power,  I'm frustrated. Beforevi got the car the po said the vaccum lines were gone though , so there maysbe the possibility that line was cutout and discarded but I'm stumped
1984 Eagle Limited

Offline amcfool1

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that looks like a piece of hard vac. line. the kind used to feed the 4wd vac system. that runs from a fitting at the very back of the intake, to the union where the red/white/yellow HARD vac lines are. If that is missing you have a vac leak. look on eaglepedia for the 4wdr vac diagram, and check it. gz

Offline rommel1940

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Now the cars acting like its flooded, will only start will gas pedel to the floor, and when it does start , it spudders and stalls , wont build rpms, did this last night, start and ran idled good this morning, annoyed.
1984 Eagle Limited

Offline rommel1940

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Re: need help, car idles fine, backfires and hesitates when throttle is applied
« Reply #10 on: December 06, 2015, 12:36:39 PM »
Will that cause it to run like poo?.nothing is missing back to the best of my knowledge
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Offline amcfool1

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Re: need help, car idles fine, backfires and hesitates when throttle is applied
« Reply #11 on: December 06, 2015, 01:14:18 PM »
choke may be stuck shut

Offline carnuck

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Re: need help, car idles fine, backfires and hesitates when throttle is applied
« Reply #12 on: December 06, 2015, 02:18:28 PM »
Or that could be to the air shut off on the air cleaner. Mine wasn't hooked up right and I went through a tank of gas in 100 miles! I replaced the aircleaner with a single heat flap "motor" instead of the double one.
AMC/Jeep gauges are for amusement only. Any correlation between them and reality is purely coincidental!

Offline rommel1940

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Re: need help, car idles fine, backfires and hesitates when throttle is applied
« Reply #13 on: December 06, 2015, 03:15:29 PM »
It runs the same with the air cleaner on or off, right now it will only run/start with the gas floored, then then it just barely runs.low rpm they won't build up, and stalls when you lift off the gas.
1984 Eagle Limited

Offline amcfool1

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Re: need help, car idles fine, backfires and hesitates when throttle is applied
« Reply #14 on: December 06, 2015, 05:16:28 PM »
ok, trying to help. is the choke closed? when you floor it, the choke mechanically opens, so, if it only runs when floored, there may be something wrong with it. You have to tell us a little more. You have to tell us if you actually tried to DO anything, besides just telling us it won't run. Problems like this are generally solved by a process of elimination. Did you check the vac system to the 4wdr? Did you you follow the vac diagram? a quick look doesn't count, trace ALL the lines according to the diagram? Try putting a screwdriver down the carb throat to hold the choke open., then crank engine w/o giving it gas. Could be a shot in the dark, but try replacing the ignition module. no wires crossed on dist, right? don't give up, the answer is there somewhere. gz

 

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