AMC Eagle Den Forum

The Mighty 258 => Fuel Systems. => Topic started by: rommel1940 on December 05, 2015, 03:27:19 PM

Title: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: rommel1940 on December 05, 2015, 03:27:19 PM
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
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: amcfool1 on December 05, 2015, 04:05:29 PM
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
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: amcfool1 on December 05, 2015, 04:17:34 PM
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
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: rommel1940 on December 05, 2015, 04:38:52 PM
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?
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: amcfool1 on December 05, 2015, 05:09:13 PM
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
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: rommel1940 on December 05, 2015, 06:41:35 PM
1984 eagle stock engine bay,  original ignition module
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: amcfool1 on December 06, 2015, 08:50:33 AM
hi, any progress?
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: rommel1940 on December 06, 2015, 10:09:52 AM
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
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: amcfool1 on December 06, 2015, 12:33:58 PM
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
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: rommel1940 on December 06, 2015, 12:35:00 PM
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.
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: rommel1940 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
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: amcfool1 on December 06, 2015, 01:14:18 PM
choke may be stuck shut
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: carnuck 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.
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: rommel1940 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.
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: amcfool1 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
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: rommel1940 on December 06, 2015, 06:13:47 PM
Sorry I've done a lot, inspected all vacuum lines,, put on a new starter solenoid and battery leads and grounds, checked the fuel filter and pump, checked the computer,poured gas down the carb to start still wouldn't start right up, will double check the choke, I appreciate all the input
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: rommel1940 on December 06, 2015, 06:21:36 PM
Ok so a screw driver down the carb and it will start and run better, idles good again, but still back fires when too much throttle is inputted.
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: carnuck on December 06, 2015, 06:50:47 PM
Could be the ignition box going bad.
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: amcfool1 on December 06, 2015, 08:51:37 PM
ok, good, a little progress! runs better with choke held open, right? ok, now you need to troubleshoot the choke system. Is it getting power? Is the pulloff working, vac line connected? Do you have a TSM? Technical Service Manual? You may want to get one, can be an invaluable tool. Check local used  book stores. Doesn't even have to be 84, (though that would be ideal) any 81/82 etc will be a help. BTW, new reprints are available online but they are expensive. also, as carnuck said still could be your ignition box, but one thing at a time. gz
Title: Re: need help, car idles fine, backfires and hesitates when throttle is applied
Post by: rommel1940 on December 06, 2015, 09:01:03 PM
Yeah thats one thing but Tennessee farmer been helping me too, we think maybe the in tank fuel filter maybe clogged, because of the backfire issue, and 2 fuel pumps on my car, will work on the possible fuel shortage and possible choke issue, I think there related, thanks for your input, I will work on the car hopefully tomorrow, weather permitting