i have a 93 eldo touiring coupe northstar w/84000 miles. was running fine then developed a misfire and rough idle. feels to me like its running on less than 8 cyls i changed plugs and wires all the coils give a strong spark still missing. no codes what should i check next?
Have you checked the DTC's?
10-30-08, 08:08 PM
Some have had problems with the ICM under the coil pack.
11-01-08, 08:44 AM
Same problem here! No problems before but suddenly misfiring on idle, in cruice no problem and fuel consuption is like before, 19mpg. No codes ofcourse! I have done complete valve job (bronze guides,new exvalves and seats)new plugs,wires and coils. Injectors cleaned and checked, difference under 2% between each injector. Replaced both oxygen sensors and catalytic converter. after these I have been driving about 1500miles without any problems (if I don't calculate transmission solenoid problem, week ago).
Now I don't know what to do or where to start?
Have there been any problems with valve lifters? Is it possible that they become to keep valves open all the time ie. not tight sealed valves? I had this valve problem 1500miles ago, all exvalves were burnt and guides worn out heavily? Am I going to have same failure again (I din't replace lifters)?:thepan:
Not sure what to tell you except that valves, valve guides and lifter problems seem to be very rare. We almost never hear of it.
11-01-08, 06:37 PM
Now I found the reason for misfiring, It was one of the new coils I replaced 1500miles ago! Bad luck that new coil fails? Coil gave strong spark when tested but when engine was running it did miss, rememer that Northstar is idling rather lean and needs extremely heavy spark to fire properly. Try to replace one coil at a time. Have you made injector power balance test to find out if there is the problem for misfiring? Anyway, try the coil first. These are only my proposals, you make your own decisions.:banghead:
11-01-08, 06:47 PM
Check your coil wiring diagram....
I replaced the entire coil pack assembly and the problem seems cured. idle is smooth no miss throughout the rpm range. i got the coil pack assy at a wrecking yard (you pull you pay) for 20$, off of a 1996 sts. seem to work fine even though some web sites indicate only 93 and 94 are interchangeable. the assy looks identical. will this be a problem?
Are you talking about the coils or the ICM? Either way, I don't think it would be a problem.