Help! Why won't my car start when cold?

[nismo1534]

1984 Chrysler Laser - Non-Turbo - Throttle Body Injection

What I know so far:

No engine fault codes
AIS Motor works
Vacuum lines have all been replaced
Brand new spark plugs
Ambient temperature above freezing when troubleshooting
No EGR valve (not sure if relevant)
No pre-heat hose (not sure if relevant)
Runs perfectly smooth when warmed up

When the car is cold I have to crank the engine for several seconds until I hear one cylinder fire. After one cylinder fires, it immediately cuts out and does not continue to fire. I then stop and wait a few seconds and repeat the process, holding the ignition on until another cylinder fires and then waiting a few seconds and trying again. I repeat this process for several minutes. Eventually all cylinders fire and the car will run for a second or two and die. I have to fight with that a few times or hold down the accelerator pedal to keep it running. Then it warms up enough to stay on by itself. Once warm, it runs absolutely perfect. I can also turn it off and turn it right back on. If I turn it off and wait several minutes it will still turn right back on.

I removed the EGR valve after installing an aftermarket exhaust manifold. I do not know if this is relevant.

I also had to remove the pre-heat hose that runs from the factory exhaust manifold to the air box. I understand that this hose feeds heated air into the engine to improve cold engine performance, but that shouldn't matter when first turning on the car, as the manifold is initially cold to begin with.

[NAJ]

84 is High Pressure TBI.
You are going to have to check fuel pressure when you are cranking and the car will not start.

[NAJ]

Also...
84-86 engine controllers are "stupid" and accept any sensor value as being correct.
So while basic ignition and fuel pressure may test ok(basics still need to be checked) you may not be getting the proper amount of fuel while cranking/running cold due to a MAP/CTS issue.

If you are in an extremely cold climate condensation may be freezing in the Map sensor line from underhood to the Map behind the R/S kick panel.
This was a common problem on 84-86 vehicles.

[detobias]

recently tuned up ? or ??

as spark plugs wear, the gap gets larger, and poor cold starting is often the first symptom..

weak Primary spark will show trouble when cold &/or wet

[nismo1534]

Brand New plugs
Ambient temperatures have been above freezing, usually around 40F

Looks like fuel pressure is the next thing to check.

[nismo1534]

Just an update, I got fed up and started throwing new parts at the car

Replaced fuel filter (old one wasn't bad though)
Replaced injector
Replaced fuel pressure regulator
Replaced MAP sensor

Something in the mix seems to have fixed the issue. It starts much easier now and stays on/holds idle, even when cold. Of course the weather is getting warmer now, so who knows!

[NAJ]

Quote:

Originally Posted by nismo1534 Of course the weather is getting warmer now, so who knows!

Well...
If the problem arises again in colder weather you need to look at the Map vacuum line for freezing moisture.
Chrysler released a TSB on this issue.
In the meantime enjoy your summer.

[turismolover22]

There were two fixes for the map sensor issue. One came in the form of a small brass vapor filter, looked a lot like a fuel filter for a lawn mower. Another fix was to move the map sensor into the engine bay, and its lines above the rest of the vacuum system, reducing the level of condensation levels in the line