258 stalls when warmed-up

[bcmjw]

Need some help / ideas please.

As a project I just picked up a 1980 CJ7 with a AMC 258 i6 / 4.2l ; over the last couple of weeks it started to run "rough." When through the simple stuff - new plugs, cap, rotor, fuel pump, fuel filter. It has now progressed to the point where it stalls when it is warm. It will run fine in high idle, but when it steps down it will run for probably 4 - 5 minutes and the stall. At that point it will re-start, but then stall again. If I let it sit for 30 minutes or so it will start right up and go through the whole cycle again. Any help would be appreciated.

bcmjw

 

[coldair]

What's the specson your setup? Running a carb?

 

[hdgapeach]

"Warm" may be a key word here. First thing I thought of was the ICM (ignition control module).

 

[Lumpy Grits]

You run'n a Carter carb?
Then look here-
Idle Problems

Get a factory shop manual ASAP-
Jeep Service Manuals

LG

 

[Torxhead]

After a stall out, or even after it runs for a short while, put your hand on the icm located behind the plastic coolant reservoir. If it is hot, that is pretty much a dead giveaway of what the problem is. I would reccomend replacing it with one from N.A.P.A., Echlin brand as you will get what you pay for providing that is what the problem is.

 

[Lumpy Grits]

How hot is the coil get'n?
Can you keep your hand on it?
LG

 

[Bent]

I think that year used a three port thermal vacuum switch for cold idle? It should be on the drivers side of the engine block just behind the power steering bracket. That switch allows manifold vacuum to advance the timing when the engine is cold. The inside port is for the ported vacuum source. the center port goes to the distributor vacuum advance and the outer port is for manifold vacuum. If the timing isn't advanced enough it will die when it switches off manifold vacuum. Hook up a timing light and see if the timing retards when it get warm. You could also try advancing the timing a little and hook up the vacuum advance directly to ported vacuum for a test.

 

[elwood blues]

"Warm" may be a key word here. First thing I thought of was the ICM (ignition control module).

Me too