Aaron came home from college over the weekend to leave his slanted '74 Dart Sport with me to diagnose and hopefully fix. He has been complaining for several weeks about how badly it has been running.

I got a good dose of it this morning on my way to work. It fired right up, idled fine through a short warm-up period, and had quick throttle response - so far, so good. I backed it out of the driveway, eased down the street to the stop sign, made the turn and drove four or five blocks to the next stop at a leisurely pace.

Then it started...
I slowed down to get over a rough RR crossing and for the next acceleration it began sputtering. I eased off the throttle for the length of the block to the stop sign, and it idled OK while stopped. I made my turn, and for the remainder of my 10-mile trip to work, it sputtered each time I pushed the throttle. The best way I can describe it is that it acts like a 4 HP Evinrude boat motor - it literally "sputters".

It is a "Super Six" with a Carter BBD 2-bbl and MOPAR electronic ignition. Just before Aaron's semester at A&M began, we had to have it worked on for carburetor problems. At that time, it would start but only run if you kept pressure on the throttle. Otherwise, it would bog down and die. It turned out that one of the brass tubes in a venturi had fallen out and wasn't siphoning fuel as it should - the carb was running too lean.

This time, it does not act the same way - it idles fine with no bogging. Are we looking at a carburetion issue, or could it be ignition? Or something else?

Any ideas are welcome,
Jerry

_________________
There's a difference between ignorance and stupidity.
Ignorance is not knowing any better.
Stupidity is knowing, yet doing it anyway.

Jerry
You are getting trash in the carb. Remember our formula of gas just changed about 6 or 7 months ago. All my rubber hoses and seals etc are starting to get eaten up.
Frank

_________________
Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

Watch out for junk in the carb when taking top off (don't invert the carb into can to empty the fuel bowl so you can see what is there).

This is reason I put EFI filter in between carb and pump. Carb's own filter is not fine enough. Also watch out that your evaporation system also get a filter between carb and the can also. I had this issue as well.

Did you pull air cleaner while engine is still hot and *recently* shut down to check on choke operation?

Cheers, Wizard

Try a different ECU and if that does not help, check the magnetic pick-up in the distributor. ( gap & resistance)
DD

I'd take a look at the Carb and make sure it doesn't have some crud in it or something hasn't become uncalibrated (I've had a BBD loosen up the adjuster screws in the bowl...that turkey got replaced, fast....)...

Like Doc said, I've seen stock EI modules go bad by dropping a cylinder here and there...after about 30 years they just don't make them like they used to...

Good Luck,

-D.Idiot

my super 6 duster has the same issue. i havent been able to pinpoint it yet other than finding the carb mounting bolts somewhat loose every now and then. i think the gasket is expanding and contracting a lot. but in the last 2 weeks i drove it daily, it would start out fine and get worse, sometimes it would get better by the time i got to work which is 35 miles. usually it wouldnt ge tbetter though. sometimes it is a slightly rough idle, but the that drives me nuts is the stumble on tip in from idle to the low speed circut. i rebuilt the carb 1-2,000 miles ago when i did the super six. im ready to chuck the carb for a big holley 2 brl. i just recurved the distirbutor to give it more initial to help with the stumble and sputtering. it doesnt fix it but will make it much easier to deal with.

Now that I've personally been able to drive it a couple of days myself, here are a few observations:

Press gas pedal down once and release to set fast idle throttle position
Fires right off on first turn of key
Idles good through warm up (1-2 minutes) - remember, central Texas
Tap throttle to drop idle down
Quick, snappy throttle response
Turn on headlights and drop into reverse - load has minimal effect
Back out of driveway, put into drive, ease down street one block just fine
Make turn onto residential street and begins the sputtering on acceleration

Sputters under light load, forcing me to feather (baby) it along to get speed
Out on highway it cruises at 65-70 fairly smoothly
Drops down into passing gear with sharp response and minimal stutter

All in all, it seems to have the most significant sputtering and stumble at low speed and under light load. Now, for the things I have checked...

Vacuum lines seem to be intact
New intake/exhaust gasket installed six weeks ago
Carb is tight on intake
Carb was adjusted six weeks ago
Plugs have been replaced in the past couple of months
New fuel filter six weeks ago

Will continue checking/trying items as suggested and as time allows.

Thanks for the input,
Jerry

_________________
There's a difference between ignorance and stupidity.
Ignorance is not knowing any better.
Stupidity is knowing, yet doing it anyway.

Next time...

When it acts up, try to keep it into that condition, put in neutral and cut the key... pull a couple of plugs and let's see what color they are...

If lean...I'm thinking the transition circuit for some reason isn't quite right since it's "off" idle... when you get down the road and get to that point what is your vaccuum gauge reading?
If this is the case...time to check and adjust the rods a bit and see if they are still in the spot they are supposed to be...



-D.Idiot

One test would be to wire the choke partially closed to see if a richer mixture reduces the sputter.
DD

I noticed this afternoon that the top nipple on the OSAC that is labeled "DIST" was not connected to a vacuum line and was sucking air. I believe it has always been that way.
The line to the vacuum diaphragm on the distributor is connected to a nipple on the upper passenger side of the Carter BBD.
A small line runs from the bottom of the OSAC to a nipple on the carb.
A small line runs from the choke pull off to a nipple on the back of the carb.
Large "BOWL VENT" and "PURGE" lines are connected properly from the carb to the charcoal canister.
A large line is connected properly from the passenger side of the carb to the PCV.

Something else I should mention...
The EGR, solenoid delay valve, vacuum amplifier, and CCEGR were never installed when we put everything back together with the '78 Super Six setup in this '74 (originally with a Holley 1bbl). It's run fine this way for almost four years.

Oh, yeah, by the way, the choke does open completely when warm.

_________________
There's a difference between ignorance and stupidity.
Ignorance is not knowing any better.
Stupidity is knowing, yet doing it anyway.

Nothing should be connected to either port of the OSAC valve. It is best bypassed altogether.
Maybe the correct one and maybe not.
We need to figure out which hose is where on the carb. In original configuration, the one and only spark advance port on the carb was connected to the OSAC valve's "CARB" connection, then a hose ran from the other end of the OSAC to the distributor. Bypassing the OSAC means running the line directly from the spark advance port to the distributor.
Sounds correct.
We'll assume they're connected to the correct carb ports...

If the car was running more or less OK and has suddenly begun running poorly, look for things that have changed. Trash in the carburetor, failing electronics, damaged wires or connections, clogged filters...and then look at fixing older errors (misconnected hook-ups and whatnot) if any exist.

_________________
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Too many people who were born on third base actually believe they've hit a triple.

This is fine, since the OSAC valve should be eliminated from the system entirely. It should be bypassed by running the hose directly from the vacuum advance pod up to the carb.
Hooray. That is possibly correct. The right nipple for the distributor is about dead center on the passenger side of the carb and only has vacuum when the throttle is opened.
Bad. This means that you have a vacuum leak. Remove the hose and cap the nipple on the carb. No hoses should be hooked to the OSAC valve.
Sounds good, so long as the nipple has full vacuum at all times.
Excellent. You might want to replace the PCV valve, just as preventatve maintenance.
Good. Just cap the vacuum fittings on the carb that are intended to feed the EGR system and you are golden.
Great, it is supposed to. You should also have installed the electric assist for the choke pulloff coil so it comes off faster.

I would suspect (a) a vacuum leak, (b) something wrong with the carb, (c) something wrong with the ignition system (control module or coil).

Heh, Dan beat me to it!

Jerry,

I second Doc's suggestion about the ECU. It is easy to check. Just plug in a known good one, make sure it is well grounded and go driving. You do do keep a couple of modules under the seat don't you?

Just leave the existing one in place and temporarily hook up the replacement.

What you described was happened to me twice.

bwhitejr

_________________
'72 Duster (Performance 360)
'83 Ramcharger (Performance 318)
'80 TrailDuster (360)
'80 D-150 Truck (See Below)
CompCams 252S, Holley 390cfm, Offy manifold
Ported, Polished and Gasket Matched
P4286813 Springs,0.040 Overbore,
0.090 Shaved Head

My experience with the ECU going bad it got progressively worse the faster you went.
Jerry
Did you replace the hoses to the tank and to the fuel pump with EI hose when you rebuilt the Dart Sport???
Frank

_________________
Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered