Chrysler Repair: 1995 Chrysler New Yorker 3.5L engine hesitation, side exhaust manifold, engine hesitation

Question
Hello:

  My 1995 New Yorker 3.5L engine frequently hesitates during acceleration at about 40 kilometres per hour(or 25mph). The engine bucks but doesn't stall and is fine at regular highway speeds. A local Chrysler dealer test drove the
car recently and hooked a diagnostic device to
a connection under the dash. Predictably, the
engine performed normally and no codes appeared
on the readout. I have also noticed that fuel
consumption is deteriorating somewhat. Spark plugs, air filter and fuel filter have all been replaced recently. What do you think could be the cause of this situation?

Answer
Hi John,
It is good that you tried to get fault codes. In their absense we need to focus on things that are less likely to be picked up by the engine controller.
The items that come to mind are the egr valve, the pcv valve and the spark coil pack.
The stem of the egr valve should be checked for whether it is able to move back and forth freely. It is located along the pipe that connects the right side exhaust manifold to the intake manifold. It has a round top mounted on flanges and inside the flange area is a rod that is the valve stem. It has a slot into which you can insert the tip of a screwdriver and use that to move the valve stem back and forth against a spring that tries to close the valve. If it is not returning fully closed, then spray some solvent such as WD-40 or carb cleaner on the stem where it enters the valve in order to free it up.
The PCV valve is located in a line between a valve cover and the intake manifold and it should be checked to verify that the ball in the valve moves freely. It is inexpensive in any case and could well be replaced.
The coil pack has 3 separate coils, with a pair of output spark wires for each pair of cylinders. If you have an ohmmeter try to measure the resistance between the pair of each of the three pairs of coil towers. They should read 7,000 to 15,000 ohms and be similar to oneanother. Then check the primary winding of each pair: remove the electrical plug-in which has a 4 wire connector. There is one pin on the coil side of the plug that is not adjacent to either the bulge on the inside or the bulge on the outside of the shell. That is the common for all three coils. Put one lead of the ohmmeter on that pin and the other on each of the other three pins in succession to see if the ohms are in the range of 0.45 to 0.65 ohms, of course after carefully zeroing the meter. If not within these values on either set of tests, then the coil pack may be why you are not getting a quality spark which is most needed when trying to accelerate.
Let me know if you have questions and how it works out, please.
The '95 should have a self-readout engine fault capability which you can do yourself: go "on-off-on-off-on and leave on", with the ignition key, within an elapased time of 5 seconds or less. Then watch the check engine light which will be 'on' to begin to flash, pause, flash, puase, etc. and count the number of flashes between each pause. Pair up those numbers to form two digit fault codes, the last of which is always 55, for "end of readout". So keep an eye on this situation yourself using that technique and let me know if you get a code other than 55. This older system is not as elaborate as the post-'96 code system. so subtle problems are not going to be noticed by it. But you can read it out for free anytime.

Roland