Chrysler Repair: 1996 Chrysler LHS: misses at idle and low speeds, side exhaust manifold, 1996 chrysler lhs

Question
The engine chugs in low speed or idling.  Mechanic ran test on the computer, found nothing.  What areas should be looked at.

Note, car has been running on Premium gas.


Answer
Hi Tim,
By "chugs" I assume that you mean it 'misses', correct?
Assuming that there is nothing the matter with the spark plugs or you don't find when you remove the spark plug wires one at a time that there is one cylinder that is the only one that is missing (e.g. that pulling the plug caps off one at a time cause the miss to get worse on all 6 plugs) then I would suspect that you exhaust gas recirculation valve is sticking ajar rather than closing tightly at idle. If however pulling one specific wire doesn't make thinks worse then I would suspect that cylinder is not firing due to a fouled plug or low compression or something else mechanical.
Take a look at the exhaust gas recirculation valve which is located behind the engine near the air intake throttle valve. It is mounted in a pipe that runs between passenger side exhaust manifold and the air intake manifold's throttle body. The valve is mounted horizontally and has a valve stem between its round vacuum actuator top and the body of the valve attached to the pipe, inside the flange that connects the two parts. The stem has a slot into which you can insert the tip of a flat-bladed screwdriver so as to lever the stem back and forth against spring action which should move freely and close tightly. If the stem seems to be sticky so that stem doesn't close all the way by spring action, then you can try spraying some penetrating solvent like WD-40 on the valve stem to freeup its motion.
If the valve is sticking slightly ajar (which is more likely the colder it gets) it will make for a rough idle/miss at low rpm such as you describe because the mixture is too dilute. It is one of the most common causes of this symptom.
So see if you can find the valve and check/lubricate the stem. To check it in motion you can rev the engine from idle to 2500 rpm and back to idle and watch to see if the valve stem moves freely in both directions to the extreme open and closed positions. It may be that the interior of the valve is cruddy so that might require that it be unbolted from the pipe where it it attached and cleaned. But chances are good it will only be a sticky stem. You will probably need to remove the corrugated air intake tube that connects the air filter housing to the throttle body air intake to the engine in order to visualize what I have described.
Feel free to write back with the results and other questions you might have.
Roland