Engine stumbles/misses almost dies...then gets better for a bit, help ! FIXED!!

[AKcharger]

I'm trying to get all the bugs out of the '72 before I leave for Korea on Sunday, thought I had them all and a new one just appeared...engine will run fine then while driving along stumbles a bit then goes back to normal. When coming to a traffic light seems to do OK then when I left off the brake and give it gas it stumbles like crazy and I have giggle the peddle to get it going...other times it's OK? Oh the idle will fluctuate too, seems to rev up when the miss starts then idle down perhaps 100-200 RPM when things are "normal" Sounds electrical to me so I bought a new ECU and it actually seems worse with the new one. Here's the story:

HISTORY
- Problem 1st occurred after a 75 mile "Confidence drive" Sunday to make sure everything was working right, car ran like a champ! just before I got home it stumbled at a traffic light once which I thought was odd but didn't think anything of it. Monday took it for a ride and notice the stumble/miss was more pronounced so ordered up a new ECU in case it got worse. Today drove it around town and it it was bad, I replaced the ECU and it got worse, or so it seemed. I was scared it would die out in traffic.
- When cold doesn't seem to do it, about 5 Min's worth of driving then it begins

Input conditions
- '77 400 stock, out of an old Cordoba
- Edlebrock 600 manual choke 1 year old
- New plugs/wires/cap/rotor/ECU/Coil as of 8 months ago...perhaps 300 miles on parts
- No engine related work or carb adjustments
- Did have Instrument cluster out but double checked all under dash connections
- stock electronic distributor

What I've tried
- Clean ECU mount area and tighten ECU
- Check Carb for sticking choke
- Disconnected vacuum advance
- inspected wires for grounding on manifolds
- Inspected coil/ECU connections
- inspected cap/rotor
- check distributor for security
- Checked dash/steering column wire connectors

Thanks for reading this far. I'm thinking the distributor but before I go blow some coin on one of those I wanted some suggestions for my fellow charger pals...guys??


Thanks in advance!

AK

[69chargeryeehaa]

did you check for a good blue spark?  like use a old plug and connect it to one wire and ground it to the block.  also did you put a timing light on it? see if it's jumping around? vacuum leak? are your wires seperated good? could be cross fireing?  that would be my next steps.

[firefighter3931]

Sounds like it's going lean off idle. Could be fuel delivery (pump or filter), float level, jetting or a vacuum leak.

Ron

[AKcharger]

All good points guys and I checked into it, here's what I did tonight
- Put timing light on it and idle and timing stayed on mark (was 10 degrees BTC but I reset it to 0 BTC) and when engine would stumble mark would move all over the place
- Tightened all connections and searched for vacuum leaks, sprayed WD-40 around carb/intake to check for leaks..nothing
- Change the carb over to an old Carter AVS I have... didn't run as good but more important did the same thing, surge, miss, stumble
- Swapped out another coil, same
- played with mixture on both carbs no difference
- Fuel filter bowl stays full of gas, looks clear
- Tapped on float bowls no difference
- I didn't check plug color
- I never messed with jetting  so I don't think that's an issue
- Oh I replaced the fuel pump when I put the engine in last year so it's kind of new
- Plug wires do touch each at places...would that cause problem? they've been that way for the past year???

I'm really leaning towards a new distributer, anyting else to check before I buy one?

Oh, one gee Whiz thing. With air cleaner off I get vacuum at the valve cover breather but my pal noticed my PVC valve was missing the check ball so it's just a elbow tube...OK, well we slaved in his PVC valve off his 318 and the vacuum on the air breather quits, does that mean anything?


Thanks guys!

[Nacho-RT74]

sooooo familar LOL...

[RECHRGD]

How old is the gas tank?  The sock could be clogging up with muck when you are stirring things up by driving around.  Does it want to miss, hesitate or stall more after you've driven a long time or given it more gas?  Bob

[AKcharger]

I replaced the fuel tank lastyear as well and it was clean...R2 the lil' sock thing too. Car will miss/stunble while normal driving but reall miss bad during accelleration. But it's intermittent, sometimes it's OK for a miute or two

Oh last night I checked for arching wires inthe dark...nothing

[Nacho-RT74]

Hi AK !!! on my thread I posted pic of where is the vent hole on gas pump ( even on my pump is on the opposite side, but same area )... is the easier to do first in my experience. Just overspray an engine cleaner can on pump and water... if you want try to clean it better, after the exterior clean just spray the hole with carb cleaner.

[AKcharger]

Hi Nacho
I was really hoping it was that was it but that hole was perfectly clear. Today I removed the fuel pump and checked for the hole, and operation...all good. I checked the fuel line for blockages at the pump to carb and also checked the lines at the fuel tank...nothing. Pulled carb off again and blew air through it to make sure nothing was blocking anything, reinstalled and nothing.

Only development is now the thing hardly starts so Monday -bad, Tuesday wore and today hardly runs...I wonder if I'm making progress? Well new fuel pump and distributor will be in tomorrow morning I guess I'll throw those on it

Anyone?

[69chargeryeehaa]

ok, you've elliminated the carb from the equation, and confident that the fuel system is ok, but your timing at 0*deg is BAD.  try setting it to 10-15*, i'd go in between at 13* initial and see how it runs there, at 0* any bb motor will run like a POS!!!!!  you may have a combination of several things contributing to your problem, but timing at 13* initial, disconnect and plug the vacuum advance, leave it plugged, (your vacuum advacne could be comming in to early or late, or advancing too much, so leave it disconnected and plugged, it will not effect performance, just give you a little better fuel economy), and then i'd go thru the carb, read your plugs and get mixtures right at idle, cruise, power mode, and of course WOT.

[AKcharger]

Hi 69 and thanks Ok tonight:
- Replaced all plugs, gaped at .035, old ones were black
- Replaced Cap and rotor
- Jumpered a wire from Pos or Batt to Pos of coil, drove it a bit not sure if it did anything bt I did notice when I removed the jumper wire the idle went UP about 200-300 RPM...put wire on RPM drops...Pull wire off RPM goes up...Does that tell me anything?

I'm going to o OHM the ballast resistor

anyone???

[Nacho-RT74]

On my gas pump, hole was clear also form outside and was pumping but too much. Dust was inside the hole.

I hope you find the fail... I know what is get mad about that.

[AKcharger]

Nah, I'm rulling out the fuel pump I remembered after I pulled it I replaced it when I put he engine in so it's ony 14 months old

Ballest resistor .007 from top and bottom prongs nothing from lt/rt prongs

I'll pull the top of the carb tomorrow and check the floats

[Nacho-RT74]

are you running a 4 or 5 pins module ?

If you are running 5 pins, the ballast is damaged to that, since needs that section working. About 5 ohms

[Just 6T9 CHGR]

Just a stab in the dark but how is your fuel pump pushrod?

[AKcharger]

Well I think it's fixed, the problem has been gone for about 20 miles now. I think the fix was the plugs but I replaced the Ballast resistor and the distributor anyway and re-adjusted the mixture to more on the lean side. Have a 200 mile trip on Saturday hope it does well and if not it's the wife's problem since I leave Saturday for a year to Korea...She can worry about it from here on out

Thanks for the inputs

AK

[AKcharger]

Nope it's back, pulled the top of the carb off and adjusted one float. Seems to run good on the highway but acts up in stop and go traffic..sometimes not. well I'm out of time, I'll play with it again in 2007

[Chryco Psycho]

Stay Safe

[AKcharger]

Found it! both wires loose off ammeter gauge. Took car to a show, got it in a spot and it died, no power to anything. Took out meter started shooting power and thought "ah...bad ammeter" Pulled radio, stuffed myself under the dash (kind of embarrassing while people are looking at the car) and note both wires to the gauge loose....hmm that might be my miss problem too! well got power back and drove 120 miles without skipping a beat now Susan will have something to drive while I'm gone.

Oh, I replaced the speedometer last week and had the cluster out, I guess I forgot to tightenthe nuts. I didn't think about it because it worked fine for like 100 miles...always check the last thing you messed with!!

[Nacho-RT74]

amazing!!! didn't you notice anything on ammeter reading before ? or hard dimming lights ? incredible stuff was that you didn't get discharged batt before find it at start moment earlier.


simply amazing and good you found it, good part of it is even was everyone looking it, you didn't need a tow to carry home the car... try to fix a new car on the street, HA!!!

[AKcharger]

Nope, the amp gauge was working as advertised showed proper charge or in the middle and slight discharge then charge with headlights on, that's why I ruled it out, I thought it would have been erratic or inop. well gotta catch a plane...talk to you guys soon

AK