1987 Fifth Avenue - VERY Rich at Warm-Up

1987 Chrysler Fifth Avenue with a 318ci V8 and a 2bbl carb. Uses the
LeanBurn system.

Runs great after it has warmed up and the idle kicks down... Gets 22 MPG.
But I noticed today that during the warm-up process that the mini cats were
glowing hot. REALLY HOT. Didn't matter if I forced the idle down or revved
it up, the engine was staying very rich and making the cats too hot. But
after the computer thought things were fine, suddenly I heard a click at the
carb and a slight buzz, then quiet... The cats cooled down.

Is there any way to keep the computer from running the engine so rich until
it determines it's warm enough to re-adjust the mixture?

I sure don't want to end up replacing three catalytic convertors!

Any ideas?

-Steve

 

This is the sort of thing that requires systematic and
procedurally-correct diagnosis. The first thing you need is the FACTORY
service manual for the car. Not Haynes, Chilton's, or any other
non-Chrysler book, you need the genuine book. If you're not willing to
wait til one shows up on Ebay, get it from your dealer.

Either your computer is not working correctly or it is seeing incorrect
information from one or more sensors. Most likely suspects are all of the
system's temperature sensors (coolant and air), closely followed by the
oxygen sensor.

You probably already need to, if they were hot enough to glow they're
almost certainly partially melted, severely restricting exhaust flow.

DS

 

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In addition I would add that the OP might want to concentrate
initially on the basic choke adjustments and whether the Air
Injection System is pumping down stream to the cats instead of up
stream to the exhaust manifolds during a cold start.

 

Excellent advice, and I'd add the choke pulloff itself to the list.

DS

 

I'd say that the original post stating that there was an audible change
when the cats quit glowing is a great indication that it IS the air
injection system sending air to the wrong place. It is possible that the
VDC solenoid in the carb makes the audible change, but in my experience
the Air Injection has a VERY audible change when switching from upstream
to downstream and vice-versa.

Of course the AIS may be working perfectly and the choke pull-off is
just allowing too much fuel in Its annoying how inter-connected
causes and effects can be.

 

H'm. The air injection (more properly, "air switching") system on my '89
318 pickup makes no sound to indicate where air is being injected. There
are systems that do have a very distinct sound to one mode that is not
present in the other, but (a) it's not the type of system installed on the
'87 318 the original poster mentions, and (b) the sound such systems make
is not a "click and buzz", and (c) the sound such systems make is not "at
the carb".

The "click and buzz at the carb" described by the OP is almost certainly
the mixture control duty cycle solenoid activating and modulating, which
it will only do in closed-loop mode, which will only be entered when the
computer senses the engine is warm enough, which will only happen if and
when all temperature-related sensors report values within certain
parameters *AND* the computer sees them accurately.

In the OP's case, it sounds as if the catalytic converters are growing
warm enough to work and/or are receiving injected air *before* the
computer enters closed-loop mode, rather than simultaneously or very
shortly afterward as is normal. The relatively high levels of unburned
fuel present in the exhaust stream in open-loop mode, particularly when/if
the choke is even partially closed, would cause the glowing catalysts.
Once the computer does enter closed-loop mode, it can strong-arm the
mixture control duty cycle solenoid into leaning the mixture enough to
compensate for even such as a partially-closed choke.

So yes, the air switching system is on the shortlist of initial systems to
check for proper functioning, but a malfunction in this system alone would
not explain the OP's symptomology. The system *is* entering closed-loop,
and once it does, everything is described as working acceptably (though
the OP's claim of 22mpg on the highway raises a couple of questions about
a sticking "all or nothing" mixture control duty cycle solenoid...). It's
just apparently not entering closed-loop as soon as it should.

I'm sticking by my original suspicion that one or more temperature
sensors, or the computer itself, is high on the list of suspected
failures.

Careful with abbreviations. AIS = Automatic Idle Speed, called by other
manufacturers IAC, Idle Air Control. The correct abbreviation for the air
injection system is AIR, left over from the days when it was known as Air
Injector Reactor.

(For those who care and don't know, the AIR systems that do change sounds
when switching modes are those that switch between injecting air into the
exhaust stream and not doing so, rather than switching between injecting
air into the exhaust stream at point "A" and injecting air into the
exhaust stream at point "B". All systems run the air pump whenever the
engine is turning, so the air has to go somewhere if it's not being
injected. The former type, when in "no injection" mode, typically routes
the air either into the engine air cleaner or to atmosphere via a muffler
or silencer of one type or another. Ford systems of the '80s and early
'90s make a very distinctive air pump noise when in "no injection" mode.)

DS

 

I disagree with that. They ALL shift sounds (to varying degrees) when
switching injection points.

and (b) the sound such systems make

Probably true, but on every 318 I've ever listened to, the air injection
is louder than the VDC solenoid. But you're right, its more of a switch
from a rasp (exhaust port injection) to a quieter hum (downstream
injection) and not a buzz or click. The old systems that dump air
overboard in one mode or the other do kinda "buzz" but they're MUCH
louder and there's little mistaking that the sound is emanating from the
valve and muffler on the side of the air injection pump.

 

!,! Awright, tough guy, c'mon up here, put a blindfold on and stand next
to my truck as I apply and remove vaccum to the switching valve and you
try to hear me doing it. There're 5-foot drifts of snow all over the
place, so bring your jacket. That's if there's any such a thing as a
"jacket" sold in your state, which I doubt 'cause y'all wouldn't know
winter if you stepped in a pile of it on the street. Oh yeah, and if you
don't stop at Kreuz' and pick me up 3 pounds of everything with extra
bread, you don't get to drive the Dart when you get here.

DS

 

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You know damn well that he's going to stay in Texas where it's
nice and toasty warm.... ;-)

 

It certainly sounds like the open-loop mixture is too rich and the ECM is
just compensating for it once it gets into closed loop. Even if it was
taking too long to go into closed loop, the mixture should not be so rich to
cause the cats to glow. The choke would certainly be a good suspect..

 

I did step in a pile of winter once... it was about 2 years ago and we
had almost a quarter inch of sleet. It was awful, think it scarred me
for life!

If I did that, I'd eat it all on the way up and I wouldn't be able to
fit in the Dart anyway.

Thpppppttttt....

 

Forget who's got the keys to the starter launcher, did we, Steve?

Ohmygaw, almost a quarter inch? Why, that's nearly six whole millimetres!
Wow, and you survived?

Oh *YEAH*?

DS

 

Daniel J. Stern wrote:

If its as cold as you say, the launcher isn't gonna start too easy. Got
an Optima in that thing?

 

An Optima with a heater, Mobil-1 5W-30, a block heater plugged into the
220 line, and SDS EFI. Oh yeah, I made a few changes while your back was
turned. It's gonna start just fine, wanna see?

WABBIT season!