Chrysler Repair: car seems to misfire at 55-60 mph, crank sensor, engine controller

Question
1995 concord 3.3L going at 55-60 will seem to stutter for a second or two . no engine lights flash on but can see a slight drop in rpms. i have replaced plugs and wires. same problem so i got a new coil pack for it... test drive did the same thing again. where to next?  any help with this would be great  thanks

Answer
Hi Farrell,
You have changed out the parts that one typically suspects for high speed missing. The only other items of an electrical sort might be either the cam or the crank sensor but I would not change those without some indication that the engine controller has detected a fault with them. You can ask the engine controller whether it has observed any failures in the control systems that are stored as codes in its memory. The most useful thing to do would be to try to get the fault codes that may stored in the engine controller memory to readout. Try using the ignition key: turn it "on-off-on-off-on" and leave it "on" (doing this quickly, no longer than 5 seconds). By "on" I mean just the normal position when the engine is running, not the cranking position. The 'check engine'light will remain on when you leave the key in the "on" position with the engine still not running. But then watch the 'check engine' light to begin flashing, then pause, flashing, pause, etc. Count the number of flashes before each pause and keep track of the numbers. Repeat the readout and verify the counts are correct. Then group them in pairs in the order that they came out, thus forming two digit numbers. You may notice that the pause is shorter between the digits of a given number, and longer between the numbers themselves. Then send me a 'follow-up' question telling me the results of your readout. By the way, 55 will be the last number (two groups of 5 flashes each) and that is the code for "end of readout". The crank fault is 11 and the cam fault code is 54
I have the troubleshooting manual for several engines and we can look up the possibilities of what is wrong based upon what fault codes you show.
There is also an essay on fault codes at the site:
http://www.allpar.com/fix/codes.html
which gives the meaning of the code numbers. But then you need to get specific info for what exactly might be the diagnostic tests or parts to replace to complete the repair.
The other possibility is with the fuel supply side, specfically a partially clogged fuel filter might cause your misfire. One of the injectors might not be doing its job reliable but catching it in the act probably requires a dynamometer to simulate road conditions.
So let me know if something interesting comes from the readout.
Roland