'78 New Yorker 440. Expert help needed.

I just bought a '78 New Yorker to pull a trailer with. All worked well when
I bought the car. I took it in for a tune up. Plugs, wires, cap, rotor. Now,
when it runs under load (pulling a trailer up a hill or just peddle to the
floor on the freeway.), it cuts off and back-fires terribly.

Is there anyone out there that has had this problem and might be able to
help?

Tad

 

Check your firing order! 18436572 most of these "techs" have never workd
on a north american V8. 5 7 are easily mixed and fire one after another.
Could be another one.
How many miles?? Could be the fuel pump!!
Also I hope they changed the fuel filter also could be the timing chain.

Dodgem

 

Does your car have the original Electronic Spark Control ignition, or
has it been replaced? My '78 Newport had some sensors fail (notably
the throttle position sensor), and wound up with symptoms a bit like
yours -- also, at idle it would start pumping out huge black clouds of
unburned rich fuel mixture (I thought my carburetor had failed and
replaced it -- symptoms continued). Installing a Mopar Performance
electronic ignition fixed it.

Anyway, the computer is located on the side of the air cleaner. Make
sure the vacuum hose connects to it properly, make sure the throttle
position sensor on the carb is hooked up properly. Put a timing light
on and see if your spark timing is stable -- that was actually what
led me to the real problem: I went to check the timing, and the spark
was bouncing randomly over about a 20 degree range.

And keep in mind the MP ignition works better than the ESC ever did,
and isn't terribly expensive, if driving is more important than a
correct restoration.

 

Blargh. Sounds like your "tune up" place might have been in over their
head with your older car. Where'd you take it?

It's possible the tech screwed something basic up. Probably not
improperly-ordered spark plug wires as someone else suggested; if it were
that the engine would run poorly all the time, not just under full
throttle. But a recheck of all the basics is a good place to start.

That said, your '78 New Yorker almost certainly has the Electronic Lean
Burn system. (Open the hood; the computer is attached to the side of the
air cleaner and has a big "LEAN BURN" sticker on it). This was Chrysler's
first effort at reducing exhaust emissions by means of electronic engine
management, and it succeeded at that task rather well, but the "brain box"
is rather simpleminded and at this point rather geriatric, and tuning a
Lean Burn car is *not* the same as tuning a regular car -- much of that
knowledge is no longer in general circulation at "just any ol' garage".

Don't know what state you're in and what kind of emissions regulations you
have to comply with, but in the end, if it is permissible where you are,
you may well wind up removing the Lean Burn system and going to a
conventional distributor and/or carburetor for vastly better driveability,
performance and mileage. Others (Steve? Joe?) can probably chime in here.

DS

 

Just as an aside, the Electronic Spark Control I mentioned was part of
the Electronic Lean Burn System. Lean Burn just meant the carb ran a
leaner mixture than before; it isn't any sort of
electrically-controlled carb (like the later feedback carburetors).
The brain box (one of the first automotive computers -- an analog
computer, yet!) only controls the spark timing.

The FSM gives a long procedure for adjusting the idle mixture using
propane for enrichment, which I found useless. In fairness, I wasn't
able to find a real propane enrichment setup and tried to do it with a
rubber hose leading from my propane tank... all the same, I finally
got it pretty good using standard "tune for manifold vacuum"
procedures (and a lot of help from Dan, Steve, and Dave who pointed
out some very stupid assumptions I was making about tuning up a car
with an automatic transmission), and got it as good as I think I'll
ever get it by having an oxygen sensor welded to my exhaust pipe and
watching a voltmeter while driving. Still a bit rough at idle,
though...

 

That's true and correct -- and if I'm not mistaken, some of the brain box
decals said "LEAN BURN" and others said "ELECTRONIC SPARK CONTROL".

 

Mine says "ELECTRONIC LEAN BURN SYSTEM" on the top of the air cleaner
housing, and "ELECTRONIC SPARK CONTROL SYSTEM" on the brain box. I
have a '78 New Yorker/Newport brochure with a picture of the brain box
in it; that one says "SPARK CONTROL COMPUTER SOLID STATE". No idea
what really went on any other car but mine.

 

Ask and ye shall recieve.

Thanks guys for all the help. It only has 84k miles. Its in very nice
condition with a few minor problems that I may or may not take care of. This
car was purchased with the intent of pulling a trailer. Big engine, lots of
power, pull trailer.

I should have mentioned that after the tuneup, on the maiden voyage is when
the thing died the first time. The first shop to look at it at that point
put a new Lean Burn (or what ever you want to call it.) computer and coil
in. That hepled, but it still cut out under full load.

The place that has it now is suggesting pulling the lean burn system out and
replacing it with a 3rd party distrubutor and ingnition. I think thats what
I'm going to have done.

Anybody need a 3 day old Lean Burn Computer?

I was in highschool in 1978 and I guess I wasn't paying attention to the
emmissions controls that were being mandated. I'm finding that this
particular era of Chrysler is not the pride of the American automotive
industry. I had a '78 Civic that ran for 200k miles and never cut out. But
then I couldn't pull a 5,000 lb. trailer with that.

Tad

 

NO. Do not use a "3rd party" anything. Use a genuine Chrysler distributor,
control box and wiring harness. Parts are standardized and available
everywhere, reliability is proven, and cost is low.

 

Timing too advanced, spark plug gap incorrect, spark plug wires with too
much resistance, distributor cap cracked or carbon-tracked, or installed
wrong, incorrect rotor, etc. etc. etc. Its almost certainly an ignition
problem since it appeared at the time of a "tune up." COULD be a
coincidental fuel problem (restricted fuel filter, weak fuel pump) but I
doubt it. Sounds like the ignition is breaking down when you run the
engine at high manifold pressure (open throttle) which makes the spark
plugs harder for the ignition system to fire in the denser charge inside
the cylinders.

 

Hey, that's a car WORTH taking care of. Sell it to one of us who will
fix it up RIGHT and buy a beater Suburban... ;-)

Don't go "third party," stick EXCLUSIVELY to Mopar parts. Mopar
Performance sells a kit to do it (like Dr. Pfeiffer suggested) or you
can scavenge a 72-75 Mopar v8 in a junkyard for all the wiring,
connectors, and ballast resistor and then buy a electronic ignition
amplifier and distributor at any parts store. Even if you go with the
whole MP "kit," the nice thing is that you can still walk into ANY parts
store and say, "Gimme a distributor cap for a '73 Charger with a 440" or
"Gimme a distributor and ignitioin modeule for a '73 Charger with a
440," and you'll get the right part. Try doing THAT when some Mallory or
Accel ignition system intended mostly for the drag strip takes a dump in
the middle of nowhere...

Nobody EVERY needed a 3 day old Lean Burn computer....

Chrysler's quality CONTROL was poor in '78, meaning that the cars varied
a lot from one to the other. That's very different from saying that the
basic design was poor- it was not. It was far better than any POS
Honda, then or now, in terms of the basic architecture of the engine and
drivetrain. If you got 200k out of a '78 Honda- congratulations, you're
a first-hand witness to a miracle. But any of the 78 Mopars that came
off the line built well (and not slapped together by hung-over
knucklee-dragging UAW types of the era who only cared about "sticking
it" to the big company) are EXPECTED to go 200k and more without trouble.

 

I'm *really* suspicious. Where on earth would they have gotten a new
spark control? I won't say it's impossible -- my Newport has a NOS
speedometer I found last Christmas -- but for a random shop to have
gone to the trouble of hunting it down seems really strange. Why did
they think it was the computer itself rather than one of the sensors
(note that the reason I pulled my computer wasn't the computer itself,
it was the throttle position sensor)?

No! If you decide to pull the spark control, put in the Mopar Performance
electronic ignition (Dan will disagree here, on the grounds that the
mechanical advance is too agressive. I haven't looked at the
advance curve and I haven't looked at the weights and magnets, but
the MP ignition works just fine for me).

*If* you're really having ignition problems, and *if* it's really the
spark computer, the problem is almost certainly that the capacitors
have had 26 years to dry out, not the miles.

But at the moment I'm inclined to think your biggest problem is your
mechanic.

 

FWIW I had a 79 LeBaron 318 with the infamous LeanBurn computer on the
air cleaner. I was getting a weird miss at highway speeds that would come
and go and it turned out to be a defective LeanBurn unit. In fact the Tech
Tips column in an old Popular Mechanics magazine nailed it to a tee.

I eventually tossed the entire lean burn system for a straight
distributer, coil, pickup and so forth and if my memory serves me correct
Chrysler even had an entire kit to rip out the Leanburn and install a
standard system.

Keep the car and toss the LeanBurn!

 

Not only "did" they make it, they still do.

http://store.summitracing.com/default.asp?target=eproduct.asp&N=120+400172+300992

 

make sure the air cleaner housing is not shorting out the coil by metal to
terinal contact