1994 Sundance stalls/runs rough when cold

Hello!

I have a 1994 Plymouth Sundance that is giving me a lot of headaches
when the weather is really cold (below freezing)... It runs rough to
begin with and when accelerating out of an intersection it often
stalls, leaving me dead in the intersection or in the middle of the
road (kind of inconvenient at times)

I have replaced Spark Plug Wires, Plugs, Rotor and Cap, PCV Valve and
hoses coming out of the valve cover (one that goes to PCV Valve and one
that goes to air cleaner) I also installed the pre-heater hose that
goes to the air cleaner as the previous owner apparently removed it.
Although the car runs a bit smoother once warmed up after all this
work, it still stalls on me. I really have no idea what else to check
and hope someone else has had this problem and knows what will fix it.
I have tried getting engine codes by turning the key on and off three
times but it comes back saying no codes stored.

If anyone can help me out, I would greatly appreciate it!

Thank you,
Kevin

 

Check your heater hose routing. There's supposed to be engine coolant
routed through the base of the intake manifold to warm it up. Also since
we know that the thermostatic air induction system was at least partially
tampered with (stove hose removed), you will want to check the operation
of the thermostatic air cleaner itself. With the engine and ambient
temperature cold, the air cleaner's damper door should block off the cold
air intake up top, and take all intake air from the stovepipe you
replaced. Just remove the stovepipe from the bottom of the air cleaner,
and remove the cold air intake pipe from the front of the air cleaner, and
cover each snorkel on the air cleaner, one at a time, with your hand to
determine which one produces suction. The system aims to keep intake air
temp at approx 100¡F, so the engine has to be good and warm, and the
ambient temperature not very cold, before the damper door moves to the
"heat off" (cold air) position.

DS

 

As far as I can see, all heater hoses are in check and there are no
problems in the cooling system (no blockages or air pockets etc) as I
just flushed the system and refilled it, making sure no air got
trapped. The damper door seems to be completely shut when I start the
car. I have yet to see it open up, but I have no watched it more than 5
mins after running. But it is taking in the air from the stove which is
what it is supposed to be doing.

The only other thing I am having a problem with, although I am not sure
if it is related, is the temperature gauge. The gauge always reads
cold. I replaced the temp. sensor and it still did that, so then I
went and replaced the gauge itself and it still doesnt work. if the car
is sitting there idling (and its usually rough) and I unplug the wire
that goes to the temp. sensor, the car seems to start running a bit
smoother and the fan starts up. If I plug it back in, the fan stops
and the engine runs a bit rough again.. is this any help?

 

The fan will turn on when you disconnect the coolant temp sensor and the
check engine lite will turn on. Your vehicle is loading up at idle, you need
to check the base engine vacuum at idle. If the engine vacuum is low (below
17) the map sensor will think that the engine is under a slight load and
cause the injector to stay open longer thus a richer mixture. Start with the
basic......Check engine timing (disconnect that coolant sensor to check
basic timing) and then vacuum.
There is also a TSB out for a cold start problem....18-08-94
Cold idle roughness (condition worse if engine speed is increased in
neutral) and poor driveability, after a cold start, in 0 to 30 degree
Fahrenheit temperatures. Condition lasts until the engine coolant
temperature reaches approximately 50 to 60 degrees Fahrenheit. Instead of
replacing the PCM, the 94 model will take a reflash. erase the software and
install the updated software. This would be considered an emission update
and should be covered under the extended warranty.

Glenn Beasley

Chrysler Tech

 

The device you unplug that starts the fan and changes the idle is the
temperature *sensor*. It talks to the SBEC (engine control computer) about
the temperature of the engine coolant, but it does not talk to the
dashboard gauge. The dashboard gauge is driven by the temperature
*sender*, which is a smaller device located not far from the sensor.